Summit Materials (SUM) 10-K 24 Feb 21 2020 FY Annual report Financial data

Cover

Cover - USD ($) $ in Billions	12 Months Ended
	Jan. 02, 2021	Feb. 22, 2021	Jun. 27, 2020
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Jan. 2, 2021
Current Fiscal Year End Date	--01-02
Document Transition Report	false
Entity File Number	001-36873
Entity Registrant Name	SUMMIT MATERIALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-1984212
Entity Address, Address Line One	1550 Wynkoop Street
Entity Address, Address Line Two	3rd Floor
Entity Address, City or Town	Denver
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80202
City Area Code	303
Local Phone Number	893-0012
Title of 12(b) Security	Class A Common Stock (par value $.01 per share)
Trading Symbol	SUM
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1.7
Documents Incorporated by Reference	Certain information required by Items 10, 11, 12, 13 and 14 of Part III incorporate information by reference from Summit Materials, Inc.’s definitive proxy statement relating to its 2021 annual meeting of stockholders to be filed with the Securities and Exchange Commission within 120 days after the close of Summit Materials, Inc.’s fiscal year.
Entity Central Index Key	0001621563
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Common Class A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		114,796,060
Common Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		99
Summit Materials, LLC
Document Information [Line Items]
Entity File Number	333-187556
Entity Registrant Name	SUMMIT MATERIALS, LLC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-4138486
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Central Index Key	0001571371
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Current assets:
Cash and cash equivalents	$ 418,181	$ 311,319
Accounts receivable, net	254,696	253,256
Costs and estimated earnings in excess of billings	8,666	13,088
Inventories	200,308	204,787
Other current assets	11,428	13,831
Total current assets	893,279	796,281
Property, plant and equipment including finance lease right-of-use assets, net	1,850,169	1,747,449
Goodwill	1,201,291	1,199,699
Intangible assets	47,852	23,498
Deferred tax assets	231,877	212,333
Operating lease right-of-use assets	28,543	32,777
Other assets	55,000	55,519
Total assets	4,308,011	4,067,556
Current liabilities:
Current portion of debt	6,354	7,942
Current portion of acquisition-related liabilities	10,265	32,700
Accounts payable	120,813	116,359
Accrued expenses	160,570	120,005
Current operating lease liabilities	8,188	8,427
Billings in excess of costs and estimated earnings	16,499	13,864
Total current liabilities	322,689	299,297
Long-term debt	1,892,347	1,851,057
Acquisition-related liabilities	12,246	19,801
Tax receivable agreement liability	321,680	326,965
Noncurrent operating lease liabilities	21,500	25,381
Other noncurrent liabilities	121,281	100,282
Total liabilities	2,691,743	2,622,783
Commitments and contingencies (see note 16)
Stockholders' equity / Member's interest
Additional paid-in capital	1,264,681	1,234,020
Accumulated earnings	326,772	188,805
Accumulated other comprehensive income	5,203	3,448
Stockholders’ equity	1,597,801	1,427,407
Noncontrolling interest in Summit Holdings	18,467	17,366
Total stockholders’ equity	1,616,268	1,444,773
Total liabilities and stockholders' equity / member's interest	4,308,011	4,067,556
Common Class A
Stockholders' equity / Member's interest
Common stock	1,145	1,134
Common Class B
Stockholders' equity / Member's interest
Common stock	0	0
Summit Materials, LLC
Current assets:
Cash and cash equivalents	418,181	311,319
Accounts receivable, net	254,696	253,256
Costs and estimated earnings in excess of billings	8,666	13,088
Inventories	200,308	204,787
Other current assets	11,428	13,831
Total current assets	893,279	796,281
Property, plant and equipment including finance lease right-of-use assets, net	1,850,169	1,747,449
Goodwill	1,202,291	1,200,699
Intangible assets	47,852	23,498
Operating lease right-of-use assets	28,543	32,777
Other assets	55,000	55,519
Total assets	4,077,134	3,856,223
Current liabilities:
Current portion of debt	6,354	7,942
Current portion of acquisition-related liabilities	7,827	30,200
Accounts payable	121,422	116,970
Accrued expenses	160,801	120,237
Current operating lease liabilities	8,188	8,427
Billings in excess of costs and estimated earnings	16,499	13,864
Total current liabilities	321,091	297,640
Long-term debt	1,892,347	1,851,057
Acquisition-related liabilities	12,246	17,666
Noncurrent operating lease liabilities	21,500	25,381
Other noncurrent liabilities	167,182	151,329
Total liabilities	2,414,366	2,343,073
Stockholders' equity / Member's interest
Member's equity	1,459,211	1,432,718
Accumulated earnings	222,140	101,403
Accumulated other comprehensive income	(18,583)	(20,971)
Total member's interest	1,662,768	1,513,150
Total liabilities and stockholders' equity / member's interest	$ 4,077,134	$ 3,856,223

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Common Class A
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	114,390,595	113,309,385	111,658,927
Common stock, shares outstanding (in shares)	114,390,595	113,309,385
Common Class B
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	99	99
Common stock, shares outstanding (in shares)	99	99

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Revenue:
Revenue	$ 2,332,451	$ 2,222,140	$ 2,101,002
Cost of revenue (excluding items shown separately below):
Cost of revenue	1,583,996	1,526,332	1,475,779
General and administrative expenses	309,531	275,813	270,402
Depreciation, depletion, amortization and accretion	221,320	217,102	204,910
Gain on sale of property, plant and equipment	(7,569)	(10,665)	(12,555)
Operating income	225,173	213,558	162,466
Interest expense	103,595	116,509	116,548
Loss on debt financings	4,064	14,565	149
Tax receivable agreement (benefit) expense	(7,559)	16,237	(22,684)
Gain on sale of business	0	0	(12,108)
Other income, net	(3,982)	(11,977)	(15,516)
Income from operations before taxes	129,055	78,224	96,077
Income tax expense (benefit)	(12,185)	17,101	59,747
Net income	141,240	61,123	36,330
Net income attributable to noncontrolling interest	3,273	2,057	2,424
Net income attributable to Summit Inc.	137,967	59,066	33,906
Summit Materials, LLC
Revenue:
Revenue	2,332,451	2,222,140	2,101,002
Cost of revenue (excluding items shown separately below):
Cost of revenue	1,583,996	1,526,332	1,475,779
General and administrative expenses	309,531	275,813	270,402
Depreciation, depletion, amortization and accretion	221,320	217,102	204,910
Gain on sale of property, plant and equipment	(7,569)	(10,665)	(12,555)
Operating income	225,173	213,558	162,466
Interest expense	103,291	115,988	115,831
Loss on debt financings	4,064	14,565	149
Gain on sale of business	0	0	(12,108)
Other income, net	(3,982)	(11,977)	(15,516)
Income from operations before taxes	121,800	94,982	74,110
Income tax expense (benefit)	1,063	6,385	10,273
Net income	120,737	88,597	63,837
Net income attributable to Summit Inc.	$ 120,737	$ 88,597	$ 63,837
Common Class A
Earnings per share of Class A common stock:
Basic (USD per share)	$ 1.21	$ 0.53	$ 0.30
Diluted (USD per share)	$ 1.20	$ 0.52	$ 0.30
Weighted average shares of Class A common stock:
Basic (in shares)	114,014,749	112,204,067	111,380,175
Diluted (in shares)	114,631,768	112,684,718	112,316,646
Common Class A and Restricted Stock
Earnings per share of Class A common stock:
Basic (USD per share)	$ 1.21	$ 0.53	$ 0.30
Weighted average shares of Class A common stock:
Basic (in shares)	114,227,192	112,204,067	111,380,175
Product
Revenue:
Revenue	$ 1,824,679	$ 1,724,462	$ 1,600,159
Cost of revenue (excluding items shown separately below):
Cost of revenue	1,166,266	1,116,662	1,058,544
Product | Summit Materials, LLC
Revenue:
Revenue	1,824,679	1,724,462	1,600,159
Cost of revenue (excluding items shown separately below):
Cost of revenue	1,166,266	1,116,662	1,058,544
Service
Revenue:
Revenue	310,075	306,185	309,099
Cost of revenue (excluding items shown separately below):
Cost of revenue	220,033	218,177	225,491
Service | Summit Materials, LLC
Revenue:
Revenue	310,075	306,185	309,099
Cost of revenue (excluding items shown separately below):
Cost of revenue	220,033	218,177	225,491
Excluding delivery and subcontract revenue
Revenue:
Revenue	2,134,754	2,030,647	1,909,258
Cost of revenue (excluding items shown separately below):
Cost of revenue	1,386,299	1,334,839	1,284,035
Excluding delivery and subcontract revenue | Summit Materials, LLC
Revenue:
Revenue	2,134,754	2,030,647	1,909,258
Cost of revenue (excluding items shown separately below):
Cost of revenue	1,386,299	1,334,839	1,284,035
Delivery and subcontract revenue
Revenue:
Revenue	197,697	191,493	191,744
Cost of revenue (excluding items shown separately below):
Cost of revenue	197,697	191,493	191,744
Delivery and subcontract revenue | Summit Materials, LLC
Revenue:
Revenue	197,697	191,493	191,744
Cost of revenue (excluding items shown separately below):
Cost of revenue	$ 197,697	$ 191,493	$ 191,744

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Net income	$ 141,240	$ 61,123	$ 36,330
Other comprehensive income (loss):
Postretirement liability adjustment	(2,229)	(1,925)	1,661
Foreign currency translation adjustment	4,617	4,716	(9,348)
Income (loss) on cash flow hedges	0	(146)
Income (loss) on cash flow hedges			1,206
Less tax effect of other comprehensive (loss) income items	(575)	0	1,578
Other comprehensive income	1,813	2,645	(4,903)
Comprehensive income	143,053	63,768	31,427
Less comprehensive income attributable to Summit Holdings	3,331	3,935	2,226
Comprehensive income attributable to Summit Materials, Inc. / Summit Materials, LLC	139,722	59,833	29,201
Summit Materials, LLC
Net income	120,737	88,597	63,837
Other comprehensive income (loss):
Postretirement liability adjustment	(2,229)	(1,925)	1,661
Foreign currency translation adjustment	4,617	4,716	(9,348)
Income (loss) on cash flow hedges	0	(146)
Income (loss) on cash flow hedges			1,206
Other comprehensive income	2,388	2,645	(6,481)
Comprehensive income attributable to Summit Materials, Inc. / Summit Materials, LLC	$ 123,125	$ 91,242	$ 57,356

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Cash flow from operating activities:
Net income	$ 141,240	$ 61,123	$ 36,330
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation, depletion, amortization and accretion	227,817	222,862	208,772
Share-based compensation expense	28,857	20,403	25,378
Net gain on asset disposals	(7,548)	(10,294)	(30,093)
Non-cash loss on debt financings	4,064	2,850	0
Change in deferred tax asset, net	(18,384)	16,012	57,490
Other	619	(2,135)	2,018
Decrease (increase) in operating assets, net of acquisitions and dispositions:
Accounts receivable, net	5,467	(37,049)	(5,796)
Inventories	3,339	8,582	(11,598)
Costs and estimated earnings in excess of billings	4,535	5,558	(8,702)
Other current assets	472	5,465	(7,159)
Other assets	10,264	5,085	(106)
(Decrease) increase in operating liabilities, net of acquisitions and dispositions:
Accounts payable	(4,231)	18,903	(13,403)
Accrued expenses	15,476	7,640	(16,544)
Billings in excess of costs and estimated earnings	2,616	1,988	(5,052)
Tax receivable agreement liability	(5,285)	17,291	(21,666)
Other liabilities	(449)	(7,100)	(501)
Net cash provided by operating activities	408,869	337,184	209,368
Cash flow from investing activities:
Acquisitions, net of cash acquired	(123,477)	(5,392)	(246,017)
Purchases of property, plant and equipment	(177,249)	(177,495)	(220,685)
Proceeds from the sale of property, plant and equipment	14,018	21,173	21,635
Proceeds from sale of business	0	0	21,564
Other	1,121	(1,095)	3,804
Net cash used in investing activities	(285,587)	(162,809)	(419,699)
Cash flow from financing activities:
Proceeds from debt issuances	700,000	300,000	64,500
Debt issuance costs	(9,605)	(6,312)	(550)
Payments on debt	(674,045)	(270,229)	(85,042)
Payments on acquisition-related liabilities	(33,257)	(33,883)	(36,504)
Distributions from partnership	0	0	(69)
Proceeds from stock option exercises	1,043	19,076	15,615
Other	(907)	(502)	(1,943)
Net cash (used in) provided by financing activities	(16,771)	8,150	(43,993)
Impact of foreign currency on cash	351	286	(724)
Net increase in cash	106,862	182,811	(255,048)
Cash and cash equivalents—beginning of period	311,319	128,508	383,556
Cash and cash equivalents—end of period	418,181	311,319	128,508
Summit Materials, LLC
Cash flow from operating activities:
Net income	120,737	88,597	63,837
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation, depletion, amortization and accretion	227,513	222,341	208,055
Share-based compensation expense	28,857	20,403	25,378
Net gain on asset disposals	(7,548)	(10,294)	(30,093)
Non-cash loss on debt financings	4,064	2,850	0
Change in deferred tax asset, net	(2,862)	6,350	9,729
Other	619	(2,135)	2,018
Decrease (increase) in operating assets, net of acquisitions and dispositions:
Accounts receivable, net	5,467	(37,049)	(5,796)
Inventories	3,339	8,582	(11,598)
Costs and estimated earnings in excess of billings	4,535	5,558	(8,702)
Other current assets	472	5,465	(7,159)
Other assets	10,264	5,085	(106)
(Decrease) increase in operating liabilities, net of acquisitions and dispositions:
Accounts payable	(4,231)	18,208	(13,989)
Accrued expenses	15,476	8,335	(16,653)
Billings in excess of costs and estimated earnings	2,616	1,988	(5,052)
Other liabilities	(449)	(7,100)	(501)
Net cash provided by operating activities	408,869	337,184	209,368
Cash flow from investing activities:
Acquisitions, net of cash acquired	(123,477)	(5,392)	(246,017)
Purchases of property, plant and equipment	(177,249)	(177,495)	(220,685)
Proceeds from the sale of property, plant and equipment	14,018	21,173	21,635
Proceeds from sale of business	0	0	21,564
Other	1,121	(1,095)	3,804
Net cash used in investing activities	(285,587)	(162,809)	(419,699)
Cash flow from financing activities:
Capital contributions by member	1,043	19,076	15,615
Proceeds from debt issuances	700,000	300,000	64,500
Debt issuance costs	(9,605)	(6,312)	(550)
Payments on debt	(674,045)	(270,229)	(85,042)
Payments on acquisition-related liabilities	(30,757)	(31,383)	(34,004)
Distributions from partnership	(2,500)	(2,500)	(2,569)
Other	(907)	(502)	(1,943)
Net cash (used in) provided by financing activities	(16,771)	8,150	(43,993)
Impact of foreign currency on cash	351	286	(724)
Net increase in cash	106,862	182,811	(255,048)
Cash and cash equivalents—beginning of period	311,319	128,508	383,556
Cash and cash equivalents—end of period	$ 418,181	$ 311,319	$ 128,508

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity / Member's Interest - USD ($) $ in Thousands	Total	Common Class A	Common Class B	Accumulated Earnings/Deficit	Accumulated Other Comprehensive Income (Loss)	Common StockCommon Class A	Common StockCommon Class B	Additional Paid-in Capital	Noncontrolling Interest	Summit Materials, LLC	Summit Materials, LLCMembers' equity	Summit Materials, LLCAccumulated Earnings/Deficit	Summit Materials, LLCAccumulated Other Comprehensive Income (Loss)
Beginning balance stockholders' equity at Dec. 30, 2017	$ 1,271,721			$ 95,833	$ 7,386	$ 1,104	$ 0	$ 1,154,220	$ 13,178
Beginning balance stockholders' equity (in shares) at Dec. 30, 2017						110,350,594	100
Beginning balance members' interest at Dec. 30, 2017										$ 1,291,594	$ 1,359,760	$ (51,031)	$ (17,135)
Increase (Decrease) In Stockholders' Equity [Rollforward]
Net contributed capital										15,615	15,615
Net income	36,330			33,906					2,424	63,837		63,837
LP Unit exchanges (in shares)						254,102
LP Unit exchanges	0					$ 2		929	(931)
Other comprehensive income (loss), net of tax	(4,903)				(4,705)				(198)	(6,481)			(6,481)
Distributions										(2,569)	(2,569)
Stock option exercises (in shares)						863,898
Stock option exercises	15,616					$ 9		15,607
Share-based compensation	25,378							25,378		25,378	25,378
Distributions from partnership	(69)								(69)
Shares redeemed to settle taxes and other (in shares)						190,333	1
Shares redeemed to settle taxes and other	(1,928)					$ 2		(1,930)		(1,943)	(1,943)
Ending balance stockholders' equity at Dec. 29, 2018	1,342,145			129,739	2,681	$ 1,117	$ 0	1,194,204	14,404				(23,616)
Ending balance stockholders' equity (in shares) at Dec. 29, 2018		111,658,927				111,658,927	99
Ending balance members' interest at Dec. 29, 2018										1,385,431	1,396,241	12,806	(23,616)
Increase (Decrease) In Stockholders' Equity [Rollforward]
Net contributed capital										19,076	19,076
Net income	61,123			59,066					2,057	88,597		88,597
LP Unit exchanges (in shares)		185,861				185,861
LP Unit exchanges	0					$ 2		971	(973)
Other comprehensive income (loss), net of tax	$ 2,645				767				1,878	2,645			2,645
Distributions										(2,500)	(2,500)
Stock option exercises (in shares)	1,065,446	1,065,446				1,065,446
Stock option exercises	$ 19,076					$ 11		19,065
Share-based compensation	20,403							20,403		20,403	20,403
Shares redeemed to settle taxes and other (in shares)		399,151				399,151	0
Shares redeemed to settle taxes and other	(619)					$ 4		(623)		(502)	(502)
Ending balance stockholders' equity at Dec. 28, 2019	1,444,773			188,805	3,448	$ 1,134	$ 0	1,234,020	17,366				(20,971)
Ending balance stockholders' equity (in shares) at Dec. 28, 2019		113,309,385	99			113,309,385	99
Ending balance members' interest at Dec. 28, 2019										1,513,150	1,432,718	101,403	(20,971)
Increase (Decrease) In Stockholders' Equity [Rollforward]
Net contributed capital										1,043	1,043
Net income	141,240									120,737		120,737
LP Unit exchanges (in shares)		376,487
Other comprehensive income (loss), net of tax	1,813									2,388			2,388
Distributions										(2,500)	(2,500)
Stock option exercises (in shares)		54,517
Share-based compensation										28,857	28,857
Shares redeemed to settle taxes and other (in shares)		650,206
Shares redeemed to settle taxes and other										(907)	(907)
Ending balance stockholders' equity at Jan. 02, 2021	$ 1,616,268			$ 326,772	$ 5,203	$ 1,145	$ 0	$ 1,264,681	$ 18,467				(18,583)
Ending balance stockholders' equity (in shares) at Jan. 02, 2021		114,390,595	99			114,390,595	99
Ending balance members' interest at Jan. 02, 2021										$ 1,662,768	$ 1,459,211	$ 222,140	$ (18,583)

Summary of Organization and Sig

Summary of Organization and Significant Accounting Policies	12 Months Ended
	Jan. 02, 2021
Company Information
Summary of Organization and Significant Accounting Policies	Summary of Organization and Significant Accounting Policies Summit Materials, Inc. (“Summit Inc.” and, together with its subsidiaries, “Summit,” “we,” “us,” “our” or the “Company”) is a vertically-integrated construction materials company. The Company is engaged in the production and sale of aggregates, cement, ready-mix concrete, asphalt paving mix and concrete products and owns and operates quarries, sand and gravel pits, two cement plants, cement distribution terminals, ready-mix concrete plants, asphalt plants and landfill sites. It is also engaged in paving and related services. The Company’s three operating and reporting segments are the West, East and Cement segments. Substantially all of the Company’s construction materials, products and services are produced, consumed and performed outdoors, primarily in the spring, summer and fall. Seasonal changes and other weather-related conditions can affect the production and sales volumes of its products and delivery of services. Therefore, the financial results for any interim period are typically not indicative of the results expected for the full year. Furthermore, the Company’s sales and earnings are sensitive to national, regional and local economic conditions, weather conditions and to cyclical changes in construction spending, among other factors. On September 23, 2014, Summit Inc. was formed as a Delaware corporation to be a holding company. Its sole material asset is a controlling equity interest in Summit Materials Holdings L.P. (“Summit Holdings”). Pursuant to a reorganization into a holding company structure (the “Reorganization”) consummated in connection with Summit Inc.’s March 2015 initial public offering ("IPO"), Summit Inc. became a holding corporation operating and controlling all of the business and affairs of Summit Holdings and its subsidiaries. Summit Inc. owns the majority of the partnership interests of Summit Holdings (see note 11, Stockholders’ Equity). Summit Materials, LLC (“Summit LLC”) an indirect wholly owned subsidiary of Summit Holdings, conducts the majority of our operations. Continental Cement Company, L.L.C. (“Continental Cement”) is also a wholly owned subsidiary of Summit LLC. Summit Materials Finance Corp. (“Summit Finance”), an indirect wholly owned subsidiary of Summit LLC, has jointly issued our Senior Notes as described below. Principles of Consolidation —The consolidated financial statements include the accounts of Summit Inc. and its majority owned subsidiaries. All intercompany balances and transactions have been eliminated. As a result of the Reorganization, Summit Holdings became a variable interest entity over which Summit Inc. has 100% voting power and control and for which Summit Inc. has the obligation to absorb losses and the right to receive benefits. The Company’s fiscal year is based on a 52-53 week year with each quarter composed of 13 weeks ending on a Saturday. The year ended January 2, 2021 was a 53-week year. For a summary of the changes in Summit Inc.’s ownership of Summit Holdings, see Note 11, Stockholders’ Equity. The Company attributes consolidated stockholders’ equity and net income separately to the controlling and noncontrolling interests. The Company accounts for investments in entities for which it has an ownership of 20% to 50% using the equity method of accounting. Use of Estimates —Preparation of these consolidated financial statements in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) requires management to make estimates and assumptions. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities and reported amounts of revenue and expenses. Such estimates include the valuation of accounts receivable, inventories, valuation of deferred tax assets, goodwill, intangibles and other long-lived assets, the tax receivable agreement (“TRA”) liability, pension and other postretirement obligations, and asset retirement obligations. Estimates also include revenue earned on contracts and costs to complete contracts. Most of the Company’s paving and related services are performed under fixed unit-price contracts with state and local governmental entities. Management regularly evaluates its estimates and assumptions based on historical experience and other factors, including the current economic environment. As future events and their effects cannot be determined with precision, actual results can differ significantly from estimates made. Changes in estimates, including those resulting from continuing changes in the economic environment, are reflected in the Company’s consolidated financial statements when the change in estimate occurs. Business and Credit Concentrations— The Company’s operations are conducted primarily across 23 U.S. states and in British Columbia, Canada, with the most significant revenue generated in Texas, Utah, Kansas and Missouri. The Company’s accounts receivable consist primarily of amounts due from customers within these areas. Therefore, collection of these accounts is dependent on the economic conditions in the aforementioned states, as well as specific situations affecting individual customers. Credit granted within the Company’s trade areas has been granted to many customers and management does not believe that a significant concentration of credit exists with respect to any individual customer or group of customers. No single customer accounted for more than 10% of the Company’s total revenue in 2020, 2019 or 2018. Accounts Receivable —Accounts receivable are stated at the amount management expects to collect from outstanding balances. Management provides for probable uncollectible amounts through a charge to earnings and a credit to a valuation allowance based on its assessment of the collectability of individual accounts. In establishing the allowance, management considers historical losses adjusted to take into account current market conditions and its customers’ financial condition, the amount of receivables in dispute, the current receivables aging and current payment terms. Balances that remain outstanding after reasonable collection efforts are exercised are written off through a charge to the valuation allowance. The balances billed but not paid by customers, pursuant to retainage provisions included in contracts, are generally due upon completion of the contracts. Revenue Recognition —We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products and plastics components, and from the provision of services, which are primarily paving and related services, but also include landfill operations, the receipt and disposal of waste that is converted to fuel for use in our cement plants. Products We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products, net of discounts or allowances, if any, and freight and delivery charges billed to customers. Revenue for product sales is recognized when evidence of an arrangement exists and when control passes, which generally is when the product is shipped. Aggregates and cement products are sold point-of-sale through purchase orders. When the product is sold on account, collectability typically occurs 30 to 60 days after the sale. Revenue is recognized when cash is received from the customer at the point of sale or when the products are delivered or collected on site. There are no other timing implications that will create a contract asset or liability, and contract modifications are unlikely given the timing and nature of the transaction. Material sales are likely to have multiple performance obligations if the product is sold with delivery. In these instances, delivery most often occurs on the same day as the control of the product transfers to the customer. As a result, even in the case of multiple performance obligations, the performance obligations are satisfied concurrently and revenue is recognized simultaneously. Services We earn revenue from the provision of services, which are primarily paving and related services, but also include landfill operations and the receipt and disposal of waste that is converted to fuel for use in our cement plants. Revenue from the receipt of waste fuels is recognized when the waste is accepted and a corresponding liability is recognized for the costs to process the waste into fuel for the manufacturing of cement or to ship the waste offsite for disposal in accordance with applicable regulations. Collectability of service contracts is due reasonably after certain milestones in the contract are performed. Milestones vary by project, but are typically calculated using monthly progress based on the percentage of completion or a customer’s engineer review of progress. The majority of the time, collection occurs within 90 days of billing and cash is received within the same fiscal year as services performed. On most projects, the customer will withhold a portion of the invoice for retainage, which may last longer than a year depending on the job. Revenue derived from paving and related services is recognized over time based on the proportion of costs incurred to date relative to the total estimated costs at completion, which approximates progress towards completion. Under this method, we recognize paving and related services revenue as services are rendered. The majority of our construction service contracts are completed within one year, but may occasionally extend beyond this time frame. The majority of our construction service contracts, and therefore, revenue, are opened and completed within one year, with most activity during the spring, summer and fall. We estimate profit as the difference between total estimated revenue and total estimated cost of a contract and recognize that profit over the life of the contract based on input measures. We generally measure progress toward completion on long- term paving and related services contracts based on the proportion of costs incurred to date relative to total estimated costs at completion. We include revisions of estimated profits on contracts in earnings under the cumulative catch-up method, under which the effect of revisions in estimates is recognized immediately. If a revised estimate of contract profitability reveals an anticipated loss on the contract, we recognize the loss in the period it is identified. The actual cost to total estimated cost method of accounting involves the use of various estimating techniques to project costs at completion, and in some cases includes estimates of recoveries asserted against the customer for changes in specifications or other disputes. Contract estimates involve various assumptions and projections relative to the outcome of future events over multiple periods, including future labor productivity and availability, the nature and complexity of the work to be performed, the cost and availability of materials, the effect of delayed performance, and the availability and timing of funding from the customer. These estimates are based on our best judgment. A significant change in one or more of these estimates could affect the profitability of one or more of our contracts. We review our contract estimates regularly to assess revisions in contract values and estimated costs at completion. Inherent uncertainties in estimating costs make it at least reasonably possible that the estimates used will change within the near term and over the life of the contracts. No material adjustments to a contract were recognized in the year ended January 2, 2021. We recognize claims when the amount of the claim can be estimated reliably and it is legally enforceable. In evaluating these criteria, we consider the contractual basis for the claim, the cause of any additional costs incurred, the reasonableness of those costs and the objective evidence available to support the claim. When the contract includes variable consideration, we estimate the amount of consideration to which we will be entitled in exchange for transferring the promised goods or services to a customer. The amount of estimated variable consideration included in the transaction price is the amount for which it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Types of variable consideration include, but are not limited to, liquidated damages and other performance penalties and production and placement bonuses. The majority of contract modifications relate to the original contract and are often an extension of the original performance obligation. Predominately, modifications are not distinct from the terms in the original contract; therefore, they are considered part of a single performance obligation. We account for the modification using a cumulative catch-up adjustment. However, there are instances where goods or services in a modification are distinct from those transferred prior to the modification. In these situations, we account for the modifications as either a separate contract or prospectively depending on the facts and circumstances of the modification. Generally, construction contracts contain mobilization costs which are categorized as costs to fulfill a contract. These costs are excluded from any measure of progress toward contract fulfillment. These costs do not result in the transfer of control of a good or service to the customer and are amortized over the life of the contract. Costs and estimated earnings in excess of billings are composed principally of revenue recognized on contracts on the percentage of completion method for which billings had not been presented to customers because the amounts were not billable under the contract terms at the balance sheet date. In accordance with the contract terms, the unbilled receivables at the balance sheet date are expected to be billed in following periods. Billings in excess of costs and estimated earnings represent billings in excess of revenue recognized. Inventories —Inventories consist of stone that has been removed from quarries and processed for future sale, cement, raw materials and finished concrete blocks. Inventories are valued at the lower of cost or net realizable value and are accounted for on a first-in first-out basis or an average cost basis. If items become obsolete or otherwise unusable or if quantities exceed what is projected to be sold within a reasonable period of time, they will be charged to costs of revenue in the period that the items are designated as obsolete or excess inventory. Stripping costs are costs of removing overburden and waste material to access aggregate materials and are expensed as incurred. Property, Plant and Equipment, net —Property, plant and equipment are recorded at cost, less accumulated depreciation, depletion and amortization. Expenditures for additions and improvements that significantly add to the productive capacity or extend the useful life of an asset are capitalized. Repair and maintenance costs that do not substantially expand productive capacity or extend the life of property, plant and equipment are expensed as incurred. Landfill airspace is included in property, plant and equipment at cost and is amortized based on the portion of the airspace used during the period compared to the gross estimated value of available airspace, which is updated periodically as circumstances dictate. Management reassesses the landfill airspace capacity with any changes in value recorded in cost of revenue. Capitalized landfill costs include expenditures for the acquisition of land and related airspace, engineering and permitting costs, cell construction costs and direct site improvement costs. Upon disposal of an asset, the cost and related accumulated depreciation are removed from the Company’s accounts and any gain or loss is included in general and administrative expenses. The Company reviews the carrying value of property, plant and equipment for impairment whenever events or circumstances indicate that the carrying value of an asset may not be recoverable from the estimated future cash flows expected to result from its use and eventual disposition. Such indicators may include, among others, deterioration in general economic conditions, adverse changes in the markets in which an entity operates, increases in input costs that have a negative effect on earnings and cash flows or a trend of negative or declining cash flows over multiple periods. Property, plant and equipment is tested for impairment at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets. As a result, the property, plant and equipment impairment test is at a significantly lower level than the level at which goodwill is tested for impairment. In markets where the Company does not produce downstream products, such as ready-mix concrete, asphalt paving mix and paving and related services, the lowest level of largely independent identifiable cash flows is at the individual aggregates operation or a group of aggregates operations collectively serving a local market or the cement operations. Conversely, in vertically-integrated markets, the cash flows of the downstream and upstream businesses are not largely independently identifiable and the vertically-integrated operations are considered the lowest level of largely independent identifiable cash flows. Aggregates mineral bearing land and interests are included in property, plant and equipment. When leased mineral interests are acquired during a business combination, they are valued using an excess earnings approach for the life of the proven and probable reserves. Depletion expense is recorded using a units of production methodology. Accrued Mining and Landfill Reclamation —The mining reclamation reserve and financial commitments for landfill closure and post-closure activities are based on management’s estimate of future cost requirements to reclaim property at both currently operating and closed sites. Estimates of these obligations have been developed based on management’s interpretation of current requirements and proposed regulatory changes and are intended to approximate fair value. Costs are estimated in current dollars, inflated until the expected time of payment, and then discounted back to present value using a credit-adjusted risk-free rate on obligations of similar maturity, adjusted to reflect the Company’s credit rating. Changes in the credit-adjusted risk-free rate do not change recorded liabilities. However, subsequent increases in the recognized obligations are measured using a current credit-adjusted risk-free rate. Decreases in the recognized obligations are measured at the initial credit-adjusted risk-free rate. Significant changes in inflation rates, or the amount or, timing of future cost estimates typically result in both (1) a current adjustment to the recorded liability (and corresponding adjustment to the asset) and (2) a change in accretion of the liability and depreciation of the asset to be recorded prospectively over the remaining capacity of the unmined quarry or landfill. Goodwill —Goodwill represents the purchase price paid in excess of the fair value of net tangible and intangible assets acquired. Goodwill recorded in connection with the Company’s acquisitions is primarily attributable to the expected profitability, assembled workforces of the acquired businesses and the synergies expected to arise after the Company’s acquisition of those businesses. Goodwill is not amortized, but is tested annually for impairment as of the first day of the fourth quarter and at any time that events or circumstances indicate that goodwill may be impaired. A qualitative approach may first be applied to determine whether it is more likely than not that the estimated fair value of a reporting unit is less than its carrying amount. If, as a result of the qualitative assessment, it is determined that an impairment is more likely than not, the two-step quantitative impairment test is then performed, otherwise further analysis is not required. The two-step impairment test first identifies potential goodwill impairment for each reporting unit and then, if necessary, measures the amount of the impairment loss. Income Taxes —Summit Inc. is a corporation subject to income taxes in the United States. Certain subsidiaries, including Summit Holdings, or subsidiary groups of the Company are taxable separate from Summit Inc. The provision for income taxes, or Summit Inc.’s proportional share of the provision, are included in the Company’s consolidated financial statements. The Company’s deferred income tax assets and liabilities are computed for differences between the tax basis and financial statement amounts that will result in taxable or deductible amounts in the future. The computed deferred balances are based on enacted tax laws and applicable rates for the periods in which the differences are expected to affect taxable income. A valuation allowance is recognized for deferred tax assets if it is more likely than not that some portion or all of the net deferred tax assets will not be realized. In making such a determination, all available positive and negative evidence is considered, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines it would be able to realize its deferred tax assets for which a valuation allowance had been recorded then an adjustment would be made to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company evaluates the tax positions taken on income tax returns that remain open and positions expected to be taken on the current year tax returns to identify uncertain tax positions. Unrecognized tax benefits on uncertain tax positions are recorded on the basis of a two-step process in which (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the largest amount of tax benefit that is more than 50 percent likely to be realized is recognized. Interest and penalties related to unrecognized tax benefits are recorded in income tax expense (benefit). Tax Receivable Agreement — When Class A limited partnership units of Summit Holdings (“LP Units”) are exchanged for shares of Class A common stock of Summit Inc. or Summit Inc. purchases LP Units for cash, this results in increases in Summit Inc.’s share of the tax basis of the tangible and intangible assets, which increases the tax depreciation and amortization deductions that otherwise would not have been available to Summit Inc. These increases in tax basis and tax depreciation and amortization deductions are expected to reduce the amount of cash taxes that we would otherwise be required to pay in the future. Prior to our IPO, we entered into a TRA with the pre-IPO owners that requires us to pay the pre-IPO owners or their permitted assignees 85% of the amount of cash savings, if any, in U.S. federal, state, and local income tax that we actually realize as a result of these exchanges. These benefits include (1) increases in the tax basis of tangible and intangible assets of Summit Holdings and certain other tax benefits related to entering into the TRA, (2) tax benefits attributable to payments under the TRA, or (3) under certain circumstances such as an early termination of the TRA, we are deemed to realize, as a result of the increases in tax basis in connection with exchanges by the pre-IPO owners described above and certain other tax benefits attributable to payments under the TRA. As noted above, we periodically evaluate the realizability of the deferred tax assets resulting from the exchange of LP Units for Class A common stock. If the deferred tax assets are determined to be realizable, we then assess whether payment of amounts under the TRA have become probable. If so, we record a TRA liability equal to 85% of such deferred tax assets. In subsequent periods, we assess the realizability of all of our deferred tax assets subject to the TRA. Should we determine a deferred tax asset with a valuation allowance is realizable in a subsequent period, the related valuation allowance will be released and consideration of a corresponding TRA liability will be assessed. The realizability of deferred tax assets, including those subject to the TRA, is dependent upon the generation of future taxable income during the periods in which those deferred tax assets become deductible and consideration of prudent and feasible tax-planning strategies. The measurement of the TRA liability is accounted for as a contingent liability. Therefore, once we determine that a payment to a pre-IPO owner has become probable and can be estimated, the estimate of payment will be accrued. Earnings per Share— The Company computes basic earnings per share attributable to stockholders by dividing income attributable to Summit Inc. by the weighted-average shares of Class A common stock outstanding. Diluted earnings per share reflects the potential dilution beyond shares for basic earnings per share that could occur if securities or other contracts to issue common stock were exercised, converted into common stock, or resulted in the issuance of common stock that would have shared in the Company’s earnings. Since the Class B common stock has no economic value, those shares are not included in the weighted-average common share amount for basic or diluted earnings per share. In addition, as the shares of Class A common stock are issued by Summit Inc., the earnings and equity interests of noncontrolling interests are not included in basic earnings per share. Prior Year Reclassifications — We have reclassified transaction costs of $2.2 million and $4.2 million for the years ended 2019 and 2018, respectively, from a separate line item included in operating income to general and administrative expenses to conform to the current year presentation. In addition, we reclassified $10.7 million and $12.6 million for the years ended 2019 and 2018, respectively, of gain on sale of property, plant and equipment from general and administrative expenses to its own line item included within operating income, also to conform to the current year presentation. New Accounting Standards — In February 2016, the Financial Accounting Standards Board FASB ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet. Lessees are required to disclose more quantitative and qualitative information about the leases than current U.S. GAAP requires. The ASU and subsequent amendments issued in 2018 are effective for public entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We adopted the standard effective December 30, 2018 using the modified retrospective approach. The modified retrospective approach provides a method for recording existing leases at adoption. In addition, we elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed us to carry forward the historical lease classification. In addition, we elected the hindsight practical expedient to determine the lease term for existing leases. The most significant impact upon adoption was the recognition of $36.8 million of operating lease right-of-use assets and $36.8 million operating lease liabilities. The standard had no material impact on our statements of operations and cash flows. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, allowing more financial and nonfinancial hedging strategies to be eligible for hedge accounting. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, increasing the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which reduces the accounting complexity of implementing a cloud computing service arrangement. The ASU aligns the capitalization of implementation costs among hosting arrangements and costs incurred to develop internal-use software. We adopted this ASU in the first quarter of 2020 and the adoption of this ASU did not have a material impact on the consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework Changes to The Disclosure Requirements for Defined Benefits Plans, which modifies the disclosure requirements of employer-sponsored defined benefit and other postretirement benefits plans. The ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results.
Summit Materials, LLC
Company Information
Summary of Organization and Significant Accounting Policies	Summary of Organization and Significant Accounting Policies Summit Materials, LLC (“Summit LLC” and, together with its subsidiaries, the “Company”) is a vertically-integrated construction materials company. The Company is engaged in the production and sale of aggregates, cement, ready-mix concrete, asphalt paving mix and concrete products and owns and operates quarries, sand and gravel pits, two cement plants, cement distribution terminals, ready-mix concrete plants, asphalt plants and landfill sites. It is also engaged in paving and related services. The Company’s three operating and reporting segments are the West, East and Cement segments. Substantially all of the Company’s construction materials, products and services are produced, consumed and performed outdoors, primarily in the spring, summer and fall. Seasonal changes and other weather-related conditions can affect the production and sales volumes of its products and delivery of services. Therefore, the financial results for any interim period are typically not indicative of the results expected for the full year. Furthermore, the Company’s sales and earnings are sensitive to national, regional and local economic conditions, weather conditions and to cyclical changes in construction spending, among other factors. Summit LLC is a wholly owned indirect subsidiary of Summit Materials Holdings L.P. (“Summit Holdings”), whose primary owner is Summit Materials, Inc. (“Summit Inc.”). Summit Inc. was formed as a Delaware corporation on September 23, 2014. Its sole material asset is a controlling equity interest in Summit Holdings. Pursuant to a reorganization into a holding company structure (the “Reorganization”) in connection with Summit Inc.’s March 2015 initial public offering, Summit Inc. became a holding corporation operating and controlling all of the business and affairs of Summit Holdings and its subsidiaries, including Summit LLC. Principles of Consolidation –The consolidated financial statements include the accounts of Summit LLC and its majority owned subsidiaries. All intercompany balances and transactions have been eliminated. The Company attributes consolidated member’s interest and net income separately to the controlling and noncontrolling interests. Noncontrolling interests in consolidated subsidiaries represent a 20% ownership in Ohio Valley Asphalt, LLC and, prior to the initial public offering (“IPO”) and concurrent purchase of the noncontrolling interests Continental Cement Company, L.L.C. (“Continental Cement”), a 30% redeemable ownership in Continental Cement. The Company accounts for investments in entities for which it has an ownership of 20% to 50% using the equity method of accounting. The Company’s fiscal year is based on a 52-53 week year with each quarter composed of 13 weeks ending on a Saturday. The year ended January 2, 2021 was a 53-week year. Use of Estimates — Preparation of these consolidated financial statements in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) requires management to make estimates and assumptions. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities and reported amounts of revenue and expenses. Such estimates include the valuation of accounts receivable, inventories, valuation of deferred tax assets, goodwill, intangibles and other long-lived assets, pension and other postretirement obligations and asset retirement obligations. Estimates also include revenue earned on contracts and costs to complete contracts. Most of the Company’s paving and related services are performed under fixed unit-price contracts with state and local governmental entities. Management regularly evaluates its estimates and assumptions based on historical experience and other factors, including the current economic environment. As future events and their effects cannot be determined with precision, actual results can differ significantly from estimates made. Changes in estimates, including those resulting from continuing changes in the economic environment, are reflected in the Company’s consolidated financial statements when the change in estimate occurs. Business and Credit Concentrations— The Company’s operations are conducted primarily across 23 U.S. states and in British Columbia, Canada, with the most significant revenue generated in Texas, Utah, Kansas and Missouri. The Company’s accounts receivable consist primarily of amounts due from customers within these areas. Therefore, collection of these accounts is dependent on the economic conditions in the aforementioned states, as well as specific situations affecting individual customers. Credit granted within the Company’s trade areas has been granted to many customers and management does not believe that a significant concentration of credit exists with respect to any individual customer or group of customers. No single customer accounted for more than 10% of the Company’s total revenue in 2020, 2019 or 2018. Accounts Receivable —Accounts receivable are stated at the amount management expects to collect from outstanding balances. Management provides for probable uncollectible amounts through a charge to earnings and a credit to a valuation allowance based on its assessment of the collectability of individual accounts. In establishing the allowance, management considers historical losses adjusted to take into account current market conditions and its customers’ financial condition, the amount of receivables in dispute, the current receivables aging and current payment terms. Balances that remain outstanding after reasonable collection efforts are exercised are written off through a charge to the valuation allowance. The balances billed but not paid by customers, pursuant to retainage provisions included in contracts, are generally due upon completion of the contracts. Revenue Recognition —We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products and plastics components, and from the provision of services, which are primarily paving and related services, but also include landfill operations, the receipt and disposal of waste that is converted to fuel for use in our cement plants. Products We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products, net of discounts or allowances, if any, and freight and delivery charges billed to customers. Revenue for product sales is recognized when evidence of an arrangement exists and when control passes, which generally is when the product is shipped. Aggregates and cement products are sold point-of-sale through purchase orders. When the product is sold on account, collectability typically occurs 30 to 60 days after the sale. Revenue is recognized when cash is received from the customer at the point of sale or when the products are delivered or collected on site. There are no other timing implications that will create a contract asset or liability, and contract modifications are unlikely given the timing and nature of the transaction. Material sales are likely to have multiple performance obligations if the product is sold with delivery. In these instances, delivery most often occurs on the same day as the control of the product transfers to the customer. As a result, even in the case of multiple performance obligations, the performance obligations are satisfied concurrently and revenue is recognized simultaneously. Services We earn revenue from the provision of services, which are primarily paving and related services, but also include landfill operations and the receipt and disposal of waste that is converted to fuel for use in our cement plants. Revenue from the receipt of waste fuels is recognized when the waste is accepted and a corresponding liability is recognized for the costs to process the waste into fuel for the manufacturing of cement or to ship the waste offsite for disposal in accordance with applicable regulations. Collectability of service contracts is due reasonably after certain milestones in the contract are performed. Milestones vary by project, but are typically calculated using monthly progress based on the percentage of completion or a customer’s engineer review of progress. The majority of the time, collection occurs within 90 days of billing and cash is received within the same fiscal year as services performed. On most projects, the customer will withhold a portion of the invoice for retainage, which may last longer than a year depending on the job. Revenue derived from paving and related services is recognized over time based on the proportion of costs incurred to date relative to the total estimated costs at completion, which approximates progress towards completion. Under this method, we recognize paving and related services revenue as services are rendered. The majority of our construction service contracts are completed within one year, but may occasionally extend beyond this time frame. The majority of our construction service contracts, and therefore, revenue, are opened and completed within one year, with most activity during the spring, summer and fall. We estimate profit as the difference between total estimated revenue and total estimated cost of a contract and recognize that profit over the life of the contract based on input measures. We generally measure progress toward completion on long-term paving and related services contracts based on the proportion of costs incurred to date relative to total estimated costs at completion. We include revisions of estimated profits on contracts in earnings under the cumulative catch-up method, under which the effect of revisions in estimates is recognized immediately. If a revised estimate of contract profitability reveals an anticipated loss on the contract, we recognize the loss in the period it is identified. The actual cost to total estimated cost method of accounting involves the use of various estimating techniques to project costs at completion, and in some cases includes estimates of recoveries asserted against the customer for changes in specifications or other disputes. Contract estimates involve various assumptions and projections relative to the outcome of future events over multiple periods, including future labor productivity and availability, the nature and complexity of the work to be performed, the cost and availability of materials, the effect of delayed performance, and the availability and timing of funding from the customer. These estimates are based on our best judgment. A significant change in one or more of these estimates could affect the profitability of one or more of our contracts. We review our contract estimates regularly to assess revisions in contract values and estimated costs at completion. Inherent uncertainties in estimating costs make it at least reasonably possible that the estimates used will change within the near term and over the life of the contracts. No material adjustments to a contract were recognized in the year ended January 2, 2021. We recognize claims when the amount of the claim can be estimated reliably and it is legally enforceable. In evaluating these criteria, we consider the contractual basis for the claim, the cause of any additional costs incurred, the reasonableness of those costs and the objective evidence available to support the claim. When the contract includes variable consideration, we estimate the amount of consideration to which we will be entitled in exchange for transferring the promised goods or services to a customer. The amount of estimated variable consideration included in the transaction price is the amount for which it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Types of variable consideration include, but are not limited to, liquidated damages and other performance penalties and production and placement bonuses. The majority of contract modifications relate to the original contract and are often an extension of the original performance obligation. Predominately, modifications are not distinct from the terms in the original contract; therefore, they are considered part of a single performance obligation. We account for the modification using a cumulative catch-up adjustment. However, there are instances where goods or services in a modification are distinct from those transferred prior to the modification. In these situations, we account for the modifications as either a separate contract or prospectively depending on the facts and circumstances of the modification. Generally, construction contracts contain mobilization costs which are categorized as costs to fulfill a contract. These costs are excluded from any measure of progress toward contract fulfillment. These costs do not result in the transfer of control of a good or service to the customer and are amortized over the life of the contract. Costs and estimated earnings in excess of billings are composed principally of revenue recognized on contracts on the percentage of completion method for which billings had not been presented to customers because the amounts were not billable under the contract terms at the balance sheet date. In accordance with the contract terms, the unbilled receivables at the balance sheet date are expected to be billed in following periods. Billings in excess of costs and estimated earnings represent billings in excess of revenue recognized. Inventories —Inventories consist of stone that has been removed from quarries and processed for future sale, cement, raw materials and finished concrete blocks. Inventories are valued at the lower of cost or net realizable value and are accounted for on a first-in first-out basis or an average cost basis. If items become obsolete or otherwise unusable or if quantities exceed what is projected to be sold within a reasonable period of time, they will be charged to costs of revenue in the period that the items are designated as obsolete or excess inventory. Stripping costs are costs of removing overburden and waste material to access aggregate materials and are expensed as incurred. Property, Plant and Equipment, net —Property, plant and equipment are recorded at cost, less accumulated depreciation, depletion and amortization. Expenditures for additions and improvements that significantly add to the productive capacity or extend the useful life of an asset are capitalized. Repair and maintenance costs that do not substantially expand productive capacity or extend the life of property, plant and equipment are expensed as incurred. Landfill airspace is included in property, plant and equipment at cost and is amortized based on the portion of the airspace used during the period compared to the gross estimated value of available airspace, which is updated periodically as circumstances dictate. Management reassesses the landfill airspace capacity with any changes in value recorded in cost of revenue. Capitalized landfill costs include expenditures for the acquisition of land and related airspace, engineering and permitting costs, cell construction costs and direct site improvement costs. Upon disposal of an asset, the cost and related accumulated depreciation are removed from the Company’s accounts and any gain or loss is included in general and administrative expenses. The Company reviews the carrying value of property, plant and equipment for impairment whenever events or circumstances indicate that the carrying value of an asset may not be recoverable from the estimated future cash flows expected to result from its use and eventual disposition. Such indicators may include, among others, deterioration in general economic conditions, adverse changes in the markets in which an entity operates, increases in input costs that have a negative effect on earnings and cash flows or a trend of negative or declining cash flows over multiple periods. Property, plant and equipment is tested for impairment at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets. As a result, the property, plant and equipment impairment test is at a significantly lower level than the level at which goodwill is tested for impairment. In markets where the Company does not produce downstream products, such as ready-mix concrete, asphalt paving mix and paving and related services, the lowest level of largely independent identifiable cash flows is at the individual aggregates operation or a group of aggregates operations collectively serving a local market or the cement operations. Conversely, in vertically-integrated markets, the cash flows of the downstream and upstream businesses are not largely independently identifiable and the vertically-integrated operations are considered the lowest level of largely independent identifiable cash flows. Aggregates mineral bearing land and interests are included in property, plant and equipment. When leased mineral interests are acquired during a business combination, they are valued using an excess earnings approach for the life of the proven and probable reserves. Depletion expense is recorded using a units of production methodology. Accrued Mining and Landfill Reclamation —The mining reclamation reserve and financial commitments for landfill closure and post-closure activities are based on management’s estimate of future cost requirements to reclaim property at both currently operating and closed sites. Estimates of these obligations have been developed based on management’s interpretation of current requirements and proposed regulatory changes and are intended to approximate fair value. Costs are estimated in current dollars, inflated until the expected time of payment, and then discounted back to present value using a credit-adjusted risk-free rate on obligations of similar maturity, adjusted to reflect the Company’s credit rating. Changes in the credit-adjusted risk-free rate do not change recorded liabilities. However, subsequent increases in the recognized obligations are measured using a current credit-adjusted risk-free rate. Decreases in the recognized obligations are measured at the initial credit-adjusted risk-free rate. Significant changes in inflation rates, or the amount or, timing of future cost estimates typically result in both (1) a current adjustment to the recorded liability (and corresponding adjustment to the asset) and (2) a change in accretion of the liability and depreciation of the asset to be recorded prospectively over the remaining capacity of the unmined quarry or landfill. Goodwill —Goodwill represents the purchase price paid in excess of the fair value of net tangible and intangible assets acquired. Goodwill recorded in connection with the Company’s acquisitions is primarily attributable to the expected profitability, assembled workforces of the acquired businesses and the synergies expected to arise after the Company’s acquisition of those businesses. Goodwill is not amortized, but is tested annually for impairment as of the first day of the fourth quarter and at any time that events or circumstances indicate that goodwill may be impaired. A qualitative approach may first be applied to determine whether it is more likely than not that the estimated fair value of a reporting unit is less than its carrying amount. If, as a result of the qualitative assessment, it is determined that an impairment is more likely than not, the two-step quantitative impairment test is then performed, otherwise further analysis is not required. The two-step impairment test first identifies potential goodwill impairment for each reporting unit and then, if necessary, measures the amount of the impairment loss. Income Taxes —As a limited liability company, the Company’s federal and state income tax attributes are generally passed to its member. However, certain subsidiaries, or subsidiary groups, of the Company are taxable entities subject to income taxes in the United States and Canada, the provisions for which are included in the consolidated financial statements. Significant judgments and estimates are required in the determination of the consolidated income tax expense. The Company’s deferred income tax assets and liabilities are computed for differences between the tax basis and financial statement amounts that will result in taxable or deductible amounts in the future. The computed deferred balances are based on enacted tax laws and applicable rates for the periods in which the differences are expected to affect taxable income. A valuation allowance is recognized for deferred tax assets if it is more likely than not that some portion or all of the net deferred tax assets will not be realized. In making such a determination, all available positive and negative evidence is considered, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines it would be able to realize its deferred tax assets for which a valuation allowance had been recorded then an adjustment would be made to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company evaluates the tax positions taken on income tax returns that remain open and positions expected to be taken on the current year tax returns to identify uncertain tax positions. Unrecognized tax benefits on uncertain tax positions are recorded on the basis of a two-step process in which (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the largest amount of tax benefit that is more than 50 percent likely to be realized is recognized. Interest and penalties related to unrecognized tax benefits are recorded in income tax expense (benefit). Prior Year Reclassifications — We have reclassified transaction costs of $2.2 million and $4.2 million for the years ended 2019 and 2018, respectively, from a separate line item included in operating income to general and administrative expenses to conform to the current year presentation. In addition, we reclassified $10.7 million and $12.6 million for the years ended 2019 and 2018, respectively, of gain on sale of property, plant and equipment from general and administrative expenses to its own line item included within operating income, also to conform to the current year presentation. New Accounting Standards — In February 2016, the Financial Accounting Standards Board FASB ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet. Lessees are required to disclose more quantitative and qualitative information about the leases than current U.S. GAAP requires. The ASU and subsequent amendments issued in 2018 are effective for public entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We adopted the standard effective December 30, 2018 using the modified retrospective approach. The modified retrospective approach provides a method for recording existing leases at adoption. In addition, we elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed us to carry forward the historical lease classification. In addition, we elected the hindsight practical expedient to determine the lease term for existing leases. The most significant impact upon adoption was the recognition of $36.8 million of operating lease right-of-use assets and $36.8 million operating lease liabilities. The standard had no material impact on our statements of operations and cash flows. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, allowing more financial and nonfinancial hedging strategies to be eligible for hedge accounting. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, increasing the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which reduces the accounting complexity of implementing a cloud computing service arrangement. The ASU aligns the capitalization of implementation costs among hosting arrangements and costs incurred to develop internal-use software. We adopted this ASU in the first quarter of 2020 and the adoption of this ASU did not have a material impact on the consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework Changes to The Disclosure Requirements for Defined Benefits Plans, which modifies the disclosure requirements of employer-sponsored defined benefit and other postretirement benefits plans. The ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results.

Acquisitions

Acquisitions	12 Months Ended
	Jan. 02, 2021
Acquisitions	Acquisitions The Company has completed numerous acquisitions since its formation, which have been financed through a combination of debt and equity funding. The operations of each acquisition have been included in the Company’s consolidated results of operations since the respective closing dates of the acquisitions. The Company measures all assets acquired and liabilities assumed at their acquisition-date fair value. The purchase price allocation for the 2020 acquisitions has not yet been finalized due to the recent timing of the acquisitions. The following table summarizes the Company’s acquisitions by region and year: 2020 2019 2018 West 2 2 5 East (1) 1 — 7 ______________________ (1) In addition, the Company acquired certain assets of a small ready-mix concrete operation in the second quarter of 2018. The table below summarizes aggregated information regarding the fair values of the assets acquired and liabilities assumed as of the respective acquisition dates. 2020 2019 Financial assets $ 8,696 $ — Inventories 2,856 52 Property, plant and equipment 130,042 3,542 Other assets 2,790 — Financial liabilities (4,469) (36) Other long-term liabilities (16,069) — Net assets acquired 123,846 3,558 Goodwill — 1,834 Purchase price 123,846 5,392 Other (369) — Net cash paid for acquisitions $ 123,477 $ 5,392 Acquisition-Related Liabilities —A number of acquisition-related liabilities have been recorded subject to terms in the relevant purchase agreements, including deferred consideration and noncompete payments. Noncompete payments have been accrued where certain former owners of newly acquired companies have entered into standard noncompete arrangements. Subject to terms and conditions stated in these noncompete agreements, payments are generally made over a five-year period. Deferred consideration is purchase price consideration paid in the future as agreed to in the purchase agreement and is not contingent on future events. Deferred consideration is generally scheduled to be paid in years ranging from 5 to 20 years in annual installments. The remaining payments due under these noncompete and deferred consideration agreements are as follows: 2021 $ 9,705 2022 3,411 2023 2,657 2024 2,620 2025 2,567 Thereafter 4,454 Total scheduled payments 25,414 Present value adjustments (4,766) Total noncompete obligations and deferred consideration $ 20,648 Accretion on the deferred consideration and noncompete obligations is recorded in interest expense.
Summit Materials, LLC
Acquisitions	Acquisitions The Company has completed numerous acquisitions since its formation, which have been financed through a combination of debt and equity funding. The operations of each acquisition have been included in the Company’s consolidated results of operations since the respective closing dates of the acquisitions. The Company measures all assets acquired and liabilities assumed at their acquisition-date fair value. The purchase price allocation for the 2020 acquisitions has not yet been finalized due to the recent timing of the acquisitions. The following table summarizes the Company’s acquisitions by region and year: 2020 2019 2018 West 2 2 5 East (1) 1 — 7 ______________________ (1) In addition, the Company acquired certain assets of a small ready-mix concrete operation in the second quarter of 2018. The table below summarizes aggregated information regarding the fair values of the assets acquired and liabilities assumed as of the respective acquisition dates. 2020 2019 Financial assets $ 8,696 $ — Inventories 2,856 52 Property, plant and equipment 130,042 3,542 Other assets 2,790 — Financial liabilities (4,469) (36) Other long-term liabilities (16,069) — Net assets acquired 123,846 3,558 Goodwill — 1,834 Purchase price 123,846 5,392 Other (369) — Net cash paid for acquisitions $ 123,477 $ 5,392 Acquisition-Related Liabilities —A number of acquisition-related liabilities have been recorded subject to terms in the relevant purchase agreements, including deferred consideration and noncompete payments. Noncompete payments have been accrued where certain former owners of newly acquired companies have entered into standard noncompete arrangements. Subject to terms and conditions stated in these noncompete agreements, payments are generally made over a five-year period. Deferred consideration is purchase price consideration paid in the future as agreed to in the purchase agreement and is not contingent on future events. Deferred consideration is generally scheduled to be paid in years ranging from 5 to 20 years in annual installments. The remaining payments due under these noncompete and deferred consideration agreements are as follows: 2021 $ 7,205 2022 3,411 2023 2,657 2024 2,620 2025 2,567 Thereafter 4,454 Total scheduled payments 22,914 Present value adjustments (4,704) Total noncompete obligations and deferred consideration $ 18,210

Goodwill

Goodwill	12 Months Ended
	Jan. 02, 2021
Goodwill	Goodwill As of January 2, 2021, the Company had 11 reporting units with goodwill for which the annual goodwill impairment test was completed. We perform the annual impairment test on the first day of the fourth quarter each year. We initially perform a qualitative analysis. As a result of this analysis, it was determined that it is more likely than not that the fair value of seven reporting units were greater than its carrying value. For the remaining reporting units we perform a two-step quantitative analysis. Step 1 of that analysis compares the estimated the fair value of the reporting units using an income approach (i.e., a discounted cash flow technique) and a market approach to the carrying value of the reporting unit. If the estimated fair value exceeds its carrying value, the goodwill of the reporting unit is not considered impaired. If the carrying value of the reporting unit exceeds its fair value, we proceed to the second step to measure the amount of potential impairment loss. Based on this analysis, it was determined that the reporting units’ fair values were greater than their carrying values and no impairment charges were recognized in 2020. The accumulated impairment charges recognized in periods prior to 2018 totaled $68.2 million. These estimates of a reporting unit’s fair value involve significant management estimates and assumptions, including but not limited to sales prices of similar assets, assumptions related to future profitability, cash flows, and discount rates. These estimates are based upon historical trends, management’s knowledge and experience and overall economic factors, including projections of future earnings potential. Developing discounted future cash flow estimates in applying the income approach required management to evaluate its intermediate to longer-term strategies, including, but not limited to, estimates about revenue growth, operating margins, capital requirements, inflation and working capital management. The development of appropriate rates to discount the estimated future cash flows required the selection of risk premiums, which can materially affect the present value of estimated future cash flows. The following table presents goodwill by reportable segments and in total: West East Cement Total Balance—December 29, 2018 $ 580,567 $ 406,805 $ 204,656 $ 1,192,028 Acquisitions 1,657 3,621 — 5,278 Foreign currency translation adjustments 2,393 — — 2,393 Balance—December 28, 2019 $ 584,617 $ 410,426 $ 204,656 $ 1,199,699 Acquisitions (1) 19 — — 19 Foreign currency translation adjustments 1,573 — — 1,573 Balance—January 2, 2021 $ 586,209 $ 410,426 $ 204,656 $ 1,201,291 ______________________ (1) Reflects goodwill from 2020 acquisitions and working capital adjustments from prior year acquisitions.
Summit Materials, LLC
Goodwill	Goodwill As of January 2, 2021, the Company had 11 reporting units with goodwill for which the annual goodwill impairment test was completed. We perform the annual impairment test on the first day of the fourth quarter each year. We initially perform a qualitative analysis. As a result of this analysis, it was determined that it is more likely than not that the fair value of seven reporting units were greater than its carrying value. For the remaining reporting units we perform a two-step quantitative analysis. Step 1 of that analysis compares the estimated the fair value of the reporting units using an income approach (i.e., a discounted cash flow technique) and a market approach to the carrying value of the reporting unit. If the estimated fair value exceeds its carrying value, the goodwill of the reporting unit is not considered impaired. If the carrying value of the reporting unit exceeds its fair value, we proceed to the second step to measure the amount of potential impairment loss. Based on this analysis, it was determined that the reporting units’ fair values were greater than their carrying values and no impairment charges were recognized in 2020. The accumulated impairment charges recognized in periods prior to 2018 totaled $68.2 million. These estimates of a reporting unit’s fair value involve significant management estimates and assumptions, including but not limited to sales prices of similar assets, assumptions related to future profitability, cash flows, and discount rates. These estimates are based upon historical trends, management’s knowledge and experience and overall economic factors, including projections of future earnings potential. Developing discounted future cash flow estimates in applying the income approach required management to evaluate its intermediate to longer-term strategies, including, but not limited to, estimates about revenue growth, operating margins, capital requirements, inflation and working capital management. The development of appropriate rates to discount the estimated future cash flows required the selection of risk premiums, which can materially affect the present value of estimated future cash flows. The following table presents goodwill by reportable segments and in total: West East Cement Total Balance—December 29, 2018 $ 581,567 $ 406,805 $ 204,656 $ 1,193,028 Acquisitions 1,657 3,621 — 5,278 Foreign currency translation adjustments 2,393 — — 2,393 Balance—December 28, 2019 $ 585,617 $ 410,426 $ 204,656 $ 1,200,699 Acquisitions (1) 19 — — 19 Foreign currency translation adjustments 1,573 — — 1,573 Balance—January 2, 2021 $ 587,209 $ 410,426 $ 204,656 $ 1,202,291 ______________________ (1) Reflects goodwill from 2020 acquisitions and working capital adjustments from prior year acquisitions.

Revenue Recognition

Revenue Recognition	12 Months Ended
	Jan. 02, 2021
Revenue from External Customer [Line Items]
Revenue Recognition	Revenue Recognition We derive our revenue predominantly by selling construction materials, products and providing paving and related services. Construction materials consist of aggregates and cement. Products consist of related downstream products, including ready-mix concrete, asphalt paving mix and concrete products. Paving and related service revenue is generated primarily from the asphalt paving services that we provide, and is recognized based on the proportion of costs incurred to date relative to the total estimated costs at completion. The majority of our construction service contracts, and therefore revenue, are opened and completed within one year, with the most activity during the spring, summer and fall. Revenue by product for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 consisted of the following: 2020 2019 2018 Revenue by product*: Aggregates $ 498,007 $ 469,670 $ 373,824 Cement 257,629 266,235 258,876 Ready-mix concrete 668,060 607,622 584,114 Asphalt 349,350 330,750 301,247 Paving and related services 381,430 360,234 379,540 Other 177,975 187,629 203,401 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ * Revenue from the liquid asphalt terminals is included in asphalt revenue. The following table outlines the significant changes in contract assets and contract liability balances from December 28, 2019 to January 2, 2021. Also included in the table is the net change in the estimate as a percentage of aggregate revenue for such contracts: Costs and estimated Billings in excess earnings in of costs and excess of billings estimated earnings Balance—December 28, 2019 $ 13,088 $ 13,864 Changes in revenue billed, contract price or cost estimates (4,535) 2,616 Other 113 19 Balance—January 2, 2021 $ 8,666 $ 16,499 Accounts receivable, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Trade accounts receivable $ 191,871 $ 191,672 Construction contract receivables 47,179 47,966 Retention receivables 18,824 17,808 Receivables from related parties 1,339 1,596 Accounts receivable 259,213 259,042 Less: Allowance for doubtful accounts (4,517) (5,786) Accounts receivable, net $ 254,696 $ 253,256 Retention receivables are amounts earned by the Company but held by customers until paving and related service contracts and projects are near completion or fully completed. Amounts are generally billed and collected within one year.
Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue Recognition	Revenue Recognition We derive our revenue predominantly by selling construction materials, products and providing paving and related services. Construction materials consist of aggregates and cement. Products consist of related downstream products, including ready-mix concrete, asphalt paving mix and concrete products. Paving and related service revenue is generated primarily from the asphalt paving services that we provide, and is recognized based on the proportion of costs incurred to date relative to the total estimated costs at completion. The majority of our construction service contracts, and therefore revenue, are opened and completed within one year, with the most activity during the spring, summer and fall. Revenue by product for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 consisted of the following: 2020 2019 2018 Revenue by product*: Aggregates $ 498,007 $ 469,670 $ 373,824 Cement 257,629 266,235 258,876 Ready-mix concrete 668,060 607,622 584,114 Asphalt 349,350 330,750 301,247 Paving and related services 381,430 360,234 379,540 Other 177,975 187,629 203,401 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ *Revenue from the liquid asphalt terminals is included in asphalt revenue. The following table outlines the significant changes in contract assets and contract liability balances from December 28, 2019 to January 2, 2021. Also included in the table is the net change in the estimate as a percentage of aggregate revenue for such contracts: Costs and estimated Billings in excess earnings in of costs and excess of billings estimated earnings Balance—December 28, 2019 $ 13,088 $ 13,864 Changes in revenue billed, contract price or cost estimates (4,535) 2,616 Other 113 19 Balance—January 2, 2021 $ 8,666 $ 16,499 Accounts receivable, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Trade accounts receivable $ 191,871 $ 191,672 Construction contract receivables 47,179 47,966 Retention receivables 18,824 17,808 Receivables from related parties 1,339 1,596 Accounts receivable 259,213 259,042 Less: Allowance for doubtful accounts (4,517) (5,786) Accounts receivable, net $ 254,696 $ 253,256 Retention receivables are amounts earned by the Company but held by customers until paving and related service contracts and projects are near completion or fully completed. Amounts are generally billed and collected within one year.

Inventories

Inventories	12 Months Ended
	Jan. 02, 2021
Inventory [Line Items]
Inventories	Inventories Inventories consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Aggregate stockpiles $ 137,938 $ 140,461 Finished goods 32,993 33,023 Work in process 9,281 7,664 Raw materials 20,096 23,639 Total $ 200,308 $ 204,787
Summit Materials, LLC
Inventory [Line Items]
Inventories	Inventories Inventories consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Aggregate stockpiles $ 137,938 $ 140,461 Finished goods 32,993 33,023 Work in process 9,281 7,664 Raw materials 20,096 23,639 Total $ 200,308 $ 204,787

Property, Plant and Equipment,

Property, Plant and Equipment, net and Intangibles, net	12 Months Ended
	Jan. 02, 2021
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, net and Intangibles, net	Property, Plant and Equipment, net and Intangibles, net Property, plant and equipment, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Mineral bearing land and leased interests $ 468,966 $ 333,024 Land (non-mineral bearing) 197,432 182,065 Buildings and improvements 181,198 178,088 Plants, machinery and equipment 1,397,410 1,318,512 Mobile equipment and barges 543,133 501,809 Truck and auto fleet 56,163 54,838 Landfill airspace and improvements 52,202 49,766 Office equipment 45,942 43,155 Construction in progress 40,648 42,007 Property, plant and equipment 2,983,094 2,703,264 Less accumulated depreciation, depletion and amortization (1,132,925) (955,815) Property, plant and equipment, net $ 1,850,169 $ 1,747,449 Depreciation on property, plant and equipment, including assets subject to capital leases, is generally computed on a straight-line basis. Depletion of mineral reserves and leased mineral interests are computed based on the portion of the reserves used during the period compared to the gross estimated value of proven and probable reserves, which is updated periodically as circumstances dictate. Leasehold improvements are amortized on a straight-line basis over the lesser of the asset’s useful life or the remaining lease term. The estimated useful lives are generally as follows: Buildings and improvements 10 - 30 years Plant, machinery and equipment 7 - 20 years Office equipment 3 - 7 years Truck and auto fleet 5 - 8 years Mobile equipment and barges 6 - 8 years Landfill airspace and improvements 10 - 30 years Other 4 - 20 years Depreciation, depletion and amortization expense of property, plant and equipment was $195.3 million, $196.8 million and $199.6 million in the years ended January 2, 2021, December 28, 2019 and December 29, 2018, respectively. Property, plant and equipment at January 2, 2021 and December 28, 2019 included $92.7 million and $82.7 million, respectively, of finance leases for certain equipment and a building with accumulated amortization of $32.8 million and $24.9 million, respectively. The equipment leases generally have terms of less than five years and the building lease had an original term of 30 years. Approximately $24.6 million and $16.0 million of the future obligations associated with the finance leases are included in accrued expenses other noncurrent liabilities Assets are assessed for impairment charges when identified for disposition. The net gain from asset dispositions recognized in general and administrative expenses in fiscal years 2020, 2019 and 2018 was $7.6 million, $10.7 million and $12.6 million, respectively. No material impairment charges have been recognized on assets held for use in fiscal 2020, 2019 or 2018. Intangible Assets —The Company’s intangible assets subject to amortization are primarily composed of operating permits, mineral lease agreements and reserve rights. Operating permits relate to permitting and zoning rights acquired outside of a business combination. The assets related to mineral lease agreements reflect the submarket royalty rates paid under agreements, primarily for extracting aggregates. The values were determined as of the respective acquisition dates by a comparison of market-royalty rates. The reserve rights relate to aggregate reserves to which the Company has the rights of ownership, but does not own the reserves. The intangible assets are amortized on a straight-line basis over the lives of the leases or permits, or computed based on the portion of the reserves used during the period compared to the gross estimated value of proven and probable reserves. The following table shows intangible assets by type and in total: January 2, 2021 December 28, 2019 Gross Net Gross Net Carrying Accumulated Carrying Carrying Accumulated Carrying Amount Amortization Amount Amount Amortization Amount Operating permits $ 33,671 $ (1,207) $ 32,464 $ 6,609 $ (290) $ 6,319 Mineral leases 19,225 (7,571) 11,654 19,064 (6,408) 12,656 Reserve rights 6,234 (2,504) 3,730 6,234 (2,248) 3,986 Trade names — — — 1,000 (958) 42 Other 586 (582) 4 957 (462) 495 Total intangible assets $ 59,716 $ (11,864) $ 47,852 $ 33,864 $ (10,366) $ 23,498 Amortization expense in fiscal 2020, 2019 and 2018 was $2.7 million, $2.1 million and $1.5 million, respectively. The estimated amortization expense for intangible assets for each of the next five years and thereafter is as follows: 2021 $ 3,129 2022 3,136 2023 3,003 2024 2,908 2025 2,863 Thereafter 32,813 Total $ 47,852
Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, net and Intangibles, net	Property, Plant and Equipment, net and Intangibles, net Property, plant and equipment, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Mineral bearing land and leased interests $ 468,966 $ 333,024 Land (non-mineral bearing) 197,432 182,065 Buildings and improvements 181,198 178,088 Plants, machinery and equipment 1,397,410 1,318,512 Mobile equipment and barges 543,133 501,809 Truck and auto fleet 56,163 54,838 Landfill airspace and improvements 52,202 49,766 Office equipment 45,942 43,155 Construction in progress 40,648 42,007 Property, plant and equipment 2,983,094 2,703,264 Less accumulated depreciation, depletion and amortization (1,132,925) (955,815) Property, plant and equipment, net $ 1,850,169 $ 1,747,449 Depreciation on property, plant and equipment, including assets subject to capital leases, is generally computed on a straight-line basis. Depletion of mineral reserves and leased mineral interests are computed based on the portion of the reserves used during the period compared to the gross estimated value of proven and probable reserves, which is updated periodically as circumstances dictate. Leasehold improvements are amortized on a straight-line basis over the lesser of the asset’s useful life or the remaining lease term. The estimated useful lives are generally as follows: Buildings and improvements 10 - 30 years Plant, machinery and equipment 7 - 20 years Office equipment 3 - 7 years Truck and auto fleet 5 - 8 years Mobile equipment and barges 6 - 8 years Landfill airspace and improvements 10 - 30 years Other 4 - 20 years Depreciation, depletion and amortization expense of property, plant and equipment was $195.3 million, $196.8 million and $199.6 million in the years ended January 2, 2021, December 28, 2019 and December 29, 2018, respectively. Property, plant and equipment at January 2, 2021 and December 28, 2019 included $92.7 million and $82.7 million, respectively, of finance leases for certain equipment and a building with accumulated amortization of $32.8 million and $24.9 million, respectively. The equipment leases generally have terms of less than five years and the building lease had an original term of 30 years. Approximately $24.6 million and $16.0 million of the future obligations associated with the finance leases are included in accrued expenses other noncurrent liabilities Assets are assessed for impairment charges when identified for disposition. The net gain from asset dispositions recognized in general and administrative expenses in fiscal years 2020, 2019 and 2018 was $7.6 million, $10.7 million and $12.6 million, respectively. No material impairment charges have been recognized on assets held for use in fiscal 2020, 2019 or 2018. Intangible Assets —The Company’s intangible assets subject to amortization are primarily composed of operating permits, mineral lease agreements and reserve rights. Operating permits relate to permitting and zoning rights acquired outside of a business combination. The assets related to mineral lease agreements reflect the submarket royalty rates paid under agreements, primarily for extracting aggregates. The values were determined as of the respective acquisition dates by a comparison of market-royalty rates. The reserve rights relate to aggregate reserves to which the Company has the rights of ownership, but does not own the reserves. The intangible assets are amortized on a straight-line basis over the lives of the leases or permits, or computed based on the portion of the reserves used during the period compared to the gross estimated value of proven and probable reserves. The following table shows intangible assets by type and in total: January 2, 2021 December 28, 2019 Gross Net Gross Net Carrying Accumulated Carrying Carrying Accumulated Carrying Amount Amortization Amount Amount Amortization Amount Operating permits $ 33,671 $ (1,207) $ 32,464 $ 6,609 $ (290) $ 6,319 Mineral leases 19,225 (7,571) 11,654 19,064 (6,408) 12,656 Reserve rights 6,234 (2,504) 3,730 6,234 (2,248) 3,986 Trade names — — — 1,000 (958) 42 Other 586 (582) 4 957 (462) 495 Total intangible assets $ 59,716 $ (11,864) $ 47,852 $ 33,864 $ (10,366) $ 23,498 Amortization expense in fiscal 2020, 2019 and 2018 was $2.7 million, $2.1 million and $1.5 million, respectively. The estimated amortization expense for intangible assets for each of the next five years and thereafter is as follows: 2021 $ 3,129 2022 3,136 2023 3,003 2024 2,908 2025 2,863 Thereafter 32,813 Total $ 47,852

Accrued Expenses

Accrued Expenses	12 Months Ended
	Jan. 02, 2021
Schedule Of Accrued Expenses [Line Items]
Accrued Expenses	Accrued Expenses Accrued expenses consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Interest $ 21,860 $ 26,892 Payroll and benefits 46,026 29,356 Finance lease obligations 24,601 16,007 Insurance 18,355 14,968 Non-income taxes 15,669 7,666 Deferred asset purchase payments 9,749 3,525 Professional fees 828 902 Other (1) 23,482 20,689 Total $ 160,570 $ 120,005 ______________________ (1) Consists primarily of current portion of asset retirement obligations and miscellaneous accruals.
Summit Materials, LLC
Schedule Of Accrued Expenses [Line Items]
Accrued Expenses	Accrued Expenses Accrued expenses consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Interest $ 21,860 $ 26,892 Payroll and benefits 46,026 29,356 Finance lease obligations 24,601 16,007 Insurance 18,355 14,968 Non-income taxes 15,900 7,898 Deferred asset purchase payments 9,749 3,525 Professional fees 828 902 Other (1) 23,482 20,689 Total $ 160,801 $ 120,237 ______________________ (1) Consists primarily of current portion of asset retirement obligations and miscellaneous accruals.

Debt

Debt	12 Months Ended
	Jan. 02, 2021
Debt	Debt Debt consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Term Loan, due 2024: $616.3 million and $624.3 million, net of $0.9 million and $1.1 million discount at January 2, 2021 and December 28, 2019, respectively $ 615,425 $ 623,140 6 1⁄8% Senior Notes, due 2023: $650.0 million, net of $0.9 million discount at December 28, 2019 — 649,133 5 1⁄8% Senior Notes, due 2025 300,000 300,000 6 1⁄2% Senior Notes, due 2027 300,000 300,000 5 1⁄4% Senior Notes, due 2029 700,000 — Total 1,915,425 1,872,273 Current portion of long-term debt 6,354 7,942 Long-term debt $ 1,909,071 $ 1,864,331 The contractual payments of long-term debt, including current maturities, for the five years subsequent to January 2, 2021, are as follows: 2021 $ 6,354 2022 6,354 2023 6,354 2024 597,252 2025 300,000 Thereafter 1,000,000 Total 1,916,314 Less: Original issue net discount (889) Less: Capitalized loan costs (16,724) Total debt $ 1,898,701 Senior Notes —On August 11, 2020, Summit LLC and Summit Finance (together, the “Issuers”) issued $700.0 million in aggregate principal amount of 5.250% senior notes due January 15, 2029 (the “2029 Notes”). The 2029 Notes were issued at 100.0% of their par value with proceeds of $690.4 million, net of related fees and expenses. The 2029 Notes were issued under an indenture dated August 11, 2020 (the "2020 Indenture"). The 2020 Indenture contains covenants limiting, among other things, Summit LLC and its restricted subsidiaries’ ability to incur additional indebtedness or issue certain preferred shares, pay dividends, redeem stock or make other distributions, make certain investments, sell or transfer certain assets, create liens, consolidate, merge, sell or otherwise dispose of all or substantially all of its assets, enter into certain transactions with affiliates, and designate subsidiaries as unrestricted subsidiaries. The 2020 Indenture also contains customary events of default. Interest on the 2029 Notes is payable semi-annually on January 15 and July 15 of each year commencing on January 15, 2021. In August 2020, using the proceeds from the 2029 Notes, all of the outstanding $650.0 million 6.125% senior notes due 2023 (the “2023 Notes”) were redeemed at a price equal to par and the indenture under which the 2023 Notes were issued was satisfied and discharged. As a result of the extinguishment, charges of $4.1 million were recognized in the quarter ended September 26, 2020, which included charges of $0.8 million for the write-off of original issue discount and $3.3 million for the write-off of deferred financing fees. On March 15, 2019, the Issuers issued $300.0 million in aggregate principal amount of 6.500% senior notes due March 15, 2027 (the “2027 Notes”). The 2027 Notes were issued at 100.0% of their par value with proceeds of $296.3 million, net of related fees and expenses. The 2027 Notes were issued under an indenture dated March 25, 2019, the terms of which are generally consistent with the 2020 Indenture. Interest on the 2027 Notes is payable semi-annually on March 15 and September 15 of each year commencing on September 15, 2019. In March 2019, using the proceeds from the 2027 Notes, all of the outstanding $250.0 million 8.500% senior notes due 2022 (the “2022 Notes”) were redeemed at a price equal to par plus an applicable premium and the indenture under which the 2022 Notes were issued was satisfied and discharged. As a result of the extinguishment, charges of $14.6 million were recognized in the quarter ended March 30, 2019, which included charges of $11.7 million for the applicable redemption premium and $2.9 million for the write-off of deferred financing fees. In 2017, the Issuers issued $300.0 million of 5.125% senior notes due June 1, 2025 (the “2025 Notes”). The 2025 Notes were issued at 100.0% of their par value with proceeds of $295.4 million, net of related fees and expenses. The 2025 Notes were issued under an indenture dated June 1, 2017, the terms of which are generally consistent with the 2020 Indenture. Interest on the 2025 Notes is payable semi-annually on June 1 and December 1 of each year commencing on December 1, 2017. In 2015, the Issuers issued $650.0 million of 6.125% senior notes due July 2023 (the “2023 Notes” and collectively with the 2022 Notes and the 2027 Notes, the “Senior Notes”). Of the aggregate $650.0 million of 2023 Notes, $350.0 million were issued at par and $300.0 million were issued at 99.375% of par. The 2023 Notes were issued under an indenture dated July 8, 2015, the terms of which are generally consistent with the 2020 Indenture. The 2023 Notes were paid in full in August 2020 as noted above. As of January 2, 2021 and December 28, 2019, the Company was in compliance with all financial covenants under the applicable indentures. Senior Secured Credit Facilities — Summit LLC has credit facilities that provide for term loans in an aggregate amount of $650.0 million and revolving credit commitments in an aggregate amount of $345.0 million (the “Senior Secured Credit Facilities”). Under the Senior Secured Credit Facilities, required principal repayments of 0.25% of the refinanced aggregate amount of term debt are due on the last business day of each March, June, September and December, commencing with the March 2018 payment. The unpaid principal balance is due in full on the maturity date, which is November 21, 2024. On February 25, 2019, Summit LLC entered into Incremental Amendment No. 4 to the credit agreement governing the Senior Secured Credit Facilities (the “Credit Agreement”) which, among other things, increased the total amount available under the revolving credit facility to $345.0 million and extended the maturity date of the Credit Agreement with respect to the revolving credit commitments to February 25, 2024. The revolving credit facility bears interest per annum equal to, at Summit LLC’s option, either (i) a base rate determined by reference to the highest of (a) the federal funds rate plus 0.50%, (b) the prime rate of Bank of America, N.A. and (c) LIBOR plus 1.00%, plus an applicable margin of 2.00% for base rate loans or (ii) a LIBOR rate determined by reference to Reuters prior to the interest period relevant to such borrowing adjusted for certain additional costs plus an applicable margin of 3.00% for LIBOR rate loans. There were no outstanding borrowings under the revolving credit facility as of January 2, 2021 or December 28, 2019. As of January 2, 2021, we had remaining borrowing capacity of $329.1 million under the revolving credit facility, which is net of $15.9 million of outstanding letters of credit. The outstanding letters of credit are renewed annually and support required bonding on construction projects and the Company’s insurance liabilities. Summit LLC’s Consolidated First Lien Net Leverage Ratio, as such term is defined in the Credit Agreement, should be no greater than 4.75:1.0 as of each quarter-end. As of January 2, 2021 and December 28, 2019, Summit LLC was in compliance with all financial covenants under the Credit Agreement. Summit LLC’s wholly-owned domestic subsidiary companies, subject to certain exclusions and exceptions, are named as subsidiary guarantors of the Senior Notes and the Senior Secured Credit Facilities. In addition, Summit LLC has pledged substantially all of its assets as collateral, subject to certain exclusions and exceptions, for the Senior Secured Credit Facilities. The following table presents the activity for the deferred financing fees for the years ended January 2, 2021 and December 28, 2019: Deferred financing fees Balance—December 29, 2018 $ 15,475 Loan origination fees 6,312 Amortization (3,501) Write off of deferred financing fees (2,850) Balance—December 28, 2019 $ 15,436 Loan origination fees 9,605 Amortization (3,336) Write off of deferred financing fees (3,338) Balance—January 2, 2021 $ 18,367 Other —On January 15, 2015, the Company’s wholly-owned subsidiary in British Columbia, Canada entered into an agreement with HSBC for a (i) $6.0 million Canadian dollar (“CAD”) revolving credit commitment to be used for operating activities that bears interest per annum equal to the bank’s prime rate plus 0.20%, (ii) $0.5 million CAD revolving credit commitment to be used for capital equipment that bears interest per annum at the bank’s prime rate plus 0.90% and (iii) $0.4 million CAD revolving credit commitment to provide guarantees on behalf of that subsidiary. There were no amounts outstanding under this agreement as of January 2, 2021 or December 28, 2019.
Summit Materials, LLC
Debt	Debt Debt consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Term Loan, due 2024: $616.3 million and $624.3 million, net of $0.9 million and $1.1 million discount at January 2, 2021 and December 28, 2019, respectively $ 615,425 $ 623,140 6 1⁄8% Senior Notes, due 2023: $650.0 million, net of $0.9 million discount at December 28, 2019 — 649,133 5 1⁄8% Senior Notes, due 2025 300,000 300,000 6 1⁄2% Senior Notes, due 2027 300,000 300,000 5 1⁄4% Senior Notes, due 2029 700,000 — Total 1,915,425 1,872,273 Current portion of long-term debt 6,354 7,942 Long-term debt $ 1,909,071 $ 1,864,331 The contractual payments of long-term debt, including current maturities, for the five years subsequent to January 2, 2021, are as follows: 2021 $ 6,354 2022 6,354 2023 6,354 2024 597,252 2025 300,000 Thereafter 1,000,000 Total 1,916,314 Less: Original issue net discount (889) Less: Capitalized loan costs (16,724) Total debt $ 1,898,701 Senior Notes —On August 11, 2020, Summit LLC and Summit Finance (together, the “Issuers”) issued $700.0 million in aggregate principal amount of 5.250% senior notes due January 15, 2029 (the “2029 Notes”). The 2029 Notes were issued at 100.0% of their par value with proceeds of $690.4 million, net of related fees and expenses. The 2029 Notes were issued under an indenture dated August 11, 2020 (the "2020 Indenture"). The 2020 Indenture contains covenants limiting, among other things, Summit LLC and its restricted subsidiaries’ ability to incur additional indebtedness or issue certain preferred shares, pay dividends, redeem stock or make other distributions, make certain investments, sell or transfer certain assets, create liens, consolidate, merge, sell or otherwise dispose of all or substantially all of its assets, enter into certain transactions with affiliates, and designate subsidiaries as unrestricted subsidiaries. The 2020 Indenture also contains customary events of default. Interest on the 2029 Notes is payable semi-annually on January 15 and July 15 of each year commencing on January 15, 2021. In August 2020, using the proceeds from the 2029 Notes, all of the outstanding $650.0 million 6.125% senior notes due 2023 (the “2023 Notes”) were redeemed at a price equal to par and the indenture under which the 2023 Notes were issued was satisfied and discharged. As a result of the extinguishment, charges of $4.1 million were recognized in the quarter ended September 26, 2020, which included charges of $0.8 million for the write-off of original issue discount and $3.3 million for the write-off of deferred financing fees. On March 15, 2019, the Issuers issued $300.0 million in aggregate principal amount of 6.500% senior notes due March 15, 2027 (the “2027 Notes”). The 2027 Notes were issued at 100.0% of their par value with proceeds of $296.3 million, net of related fees and expenses. The 2027 Notes were issued under an indenture dated March 25, 2019, the terms of which are generally consistent with the 2020 Indenture. Interest on the 2027 Notes is payable semi-annually on March 15 and September 15 of each year commencing on September 15, 2019. In March 2019, using the proceeds from the 2027 Notes, all of the outstanding $250.0 million 8.500% senior notes due 2022 (the “2022 Notes”) were redeemed at a price equal to par plus an applicable premium and the indenture under which the 2022 Notes were issued was satisfied and discharged. As a result of the extinguishment, charges of $14.6 million were recognized in the quarter ended March 30, 2019, which included charges of $11.7 million for the applicable redemption premium and $2.9 million for the write-off of deferred financing fees. In 2017, the Issuers issued $300.0 million of 5.125% senior notes due June 1, 2025 (the “2025 Notes”). The 2025 Notes were issued at 100.0% of their par value with proceeds of $295.4 million, net of related fees and expenses. The 2025 Notes were issued under an indenture dated June 1, 2017, the terms of which are generally consistent with the 2020 Indenture. Interest on the 2025 Notes is payable semi-annually on June 1 and December 1 of each year commencing on December 1, 2017. In 2015, the Issuers issued $650.0 million of 6.125% senior notes due July 2023 (the “2023 Notes” and collectively with the 2022 Notes and the 2027 Notes, the “Senior Notes”). Of the aggregate $650.0 million of 2023 Notes, $350.0 million were issued at par and $300.0 million were issued at 99.375% of par. The 2023 Notes were issued under an indenture dated July 8, 2015, the terms of which are generally consistent with the 2020 Indenture. The 2023 Notes were paid in full in August 2020 as noted above. As of January 2, 2021 and December 28, 2019, the Company was in compliance with all financial covenants under the applicable indentures. Senior Secured Credit Facilities — Summit LLC has credit facilities that provide for term loans in an aggregate amount of $650.0 million and revolving credit commitments in an aggregate amount of $345.0 million (the “Senior Secured Credit Facilities”). Under the Senior Secured Credit Facilities, required principal repayments of 0.25% of the refinanced aggregate amount of term debt are due on the last business day of each March, June, September and December, commencing with the March 2018 payment. The unpaid principal balance is due in full on the maturity date, which is November 21, 2024. On February 25, 2019, Summit LLC entered into Incremental Amendment No. 4 to the credit agreement governing the Senior Secured Credit Facilities (the “Credit Agreement”) which, among other things, increased the total amount available under the revolving credit facility to $345.0 million and extended the maturity date of the Credit Agreement with respect to the revolving credit commitments to February 25, 2024. The revolving credit facility bears interest per annum equal to, at Summit LLC’s option, either (i) a base rate determined by reference to the highest of (a) the federal funds rate plus 0.50%, (b) the prime rate of Bank of America, N.A. and (c) LIBOR plus 1.00%, plus an applicable margin of 2.00% for base rate loans or (ii) a LIBOR rate determined by reference to Reuters prior to the interest period relevant to such borrowing adjusted for certain additional costs plus an applicable margin of 3.00% for LIBOR rate loans. There were no outstanding borrowings under the revolving credit facility as of January 2, 2021 or December 28, 2019. As of January 2, 2021, we had remaining borrowing capacity of $329.1 million under the revolving credit facility, which is net of $15.9 million of outstanding letters of credit. The outstanding letters of credit are renewed annually and support required bonding on construction projects and the Company’s insurance liabilities. Summit LLC’s Consolidated First Lien Net Leverage Ratio, as such term is defined in the Credit Agreement, should be no greater than 4.75:1.0 as of each quarter-end. As of January 2, 2021 and December 28, 2019, Summit LLC was in compliance with all financial covenants under the Credit Agreement. Summit LLC’s wholly-owned domestic subsidiary companies, subject to certain exclusions and exceptions, are named as subsidiary guarantors of the Senior Notes and the Senior Secured Credit Facilities. In addition, Summit LLC has pledged substantially all of its assets as collateral, subject to certain exclusions and exceptions, for the Senior Secured Credit Facilities. The following table presents the activity for the deferred financing fees for the years ended January 2, 2021 and December 28, 2019: Deferred financing fees Balance—December 29, 2018 $ 15,475 Loan origination fees 6,312 Amortization (3,501) Write off of deferred financing fees (2,850) Balance—December 28, 2019 $ 15,436 Loan origination fees 9,605 Amortization (3,336) Write off of deferred financing fees (3,338) Balance—January 2, 2021 $ 18,367 Other —On January 15, 2015, the Company’s wholly-owned subsidiary in British Columbia, Canada entered into an agreement with HSBC for a (i) $6.0 million Canadian dollar (“CAD”) revolving credit commitment to be used for operating activities that bears interest per annum equal to the bank’s prime rate plus 0.20%, (ii) $0.5 million CAD revolving credit commitment to be used for capital equipment that bears interest per annum at the bank’s prime rate plus 0.90% and (iii) $0.4 million CAD revolving credit commitment to provide guarantees on behalf of that subsidiary. There were no amounts outstanding under this agreement as of January 2, 2021 or December 28, 2019.

Income Taxes

Income Taxes	12 Months Ended
	Jan. 02, 2021
Income Taxes [Line Items]
Income Taxes	Income Taxes Summit Inc.’s tax provision includes its proportional share of Summit Holdings’ tax attributes. Summit Holdings’ subsidiaries are primarily limited liability companies, but do include certain entities organized as C corporations and a Canadian subsidiary. The tax attributes related to the limited liability companies are passed on to Summit Holdings and then to its partners, including Summit Inc. The tax attributes associated with the C corporation and Canadian subsidiaries are fully reflected in the Company’s consolidated financial statements. For the years ended January 2, 2021, December 28, 2019 and December 29, 2018, income taxes consisted of the following: 2020 2019 2018 Provision for income taxes: Current $ 3,827 $ 69 $ 463 Deferred (16,012) 17,032 59,284 Income tax expense (benefit) $ (12,185) $ 17,101 $ 59,747 The effective tax rate on pre-tax income differs from the U.S. statutory rate of 21% for 2020, 2019 and 2018, respectively, due to the following: 2020 2019 2018 Income tax expense (benefit) at federal statutory tax rate $ 27,100 $ 16,427 $ 20,177 Less: Income tax benefit at federal statutory tax rate for LLC entities (593) (658) (561) State and local income taxes 5,067 3,792 4,894 Permanent differences (3,345) (6,272) (5,537) Effective tax rate change 4,257 (2,006) 4,034 Unrecognized tax benefits (41,548) 18,885 22,663 Tax receivable agreement (benefit) expense (6) 2,436 (8,282) Change in valuation allowance — (17,691) 17,592 Other (3,117) 2,188 4,767 Income tax expense (benefit) $ (12,185) $ 17,101 $ 59,747 The following table summarizes the components of the net deferred income tax asset (liability) as January 2, 2021 and December 28, 2019: 2020 2019 Deferred tax assets (liabilities): Net intangible assets $ 199,497 $ 240,790 Accelerated depreciation (209,644) (201,126) Net operating loss 227,560 164,335 Investment in limited partnership (33,139) (31,987) Mining reclamation reserve 3,306 2,018 Working capital (e.g., accrued compensation, prepaid assets) 45,972 37,287 Interest expense limitation carryforward — 2,691 Less valuation allowance (1,675) (1,675) Deferred tax assets 231,877 212,333 Less foreign deferred tax liability (included in other noncurrent liabilities) (18,393) (8,267) Net deferred tax asset $ 213,484 $ 204,066 As of January 2, 2021, $378.5 million of our deferred tax assets subject to our TRA are included in the net intangible assets and the net operating loss line items above. Our income tax expense (benefit) was $(12.2) million, $17.1 million and $59.7 million in the fiscal years ended 2020, 2019 and 2018, respectively. Our effective income tax rate in 2020 and 2019 was impacted by the IRS interpretative guidance of TCJA, a change in state tax rates and a change in the amount of our TRA liability. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible, as well as consideration of tax-planning strategies we may seek to utilize net operating loss carryforwards that begin to expire in 2030. The Company updates the analysis, and adjusted the valuation allowance for interest expense carryforwards limited under the TCJA based on updated forecast models each year. On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (“TCJA”) was enacted. Among other things, the TCJA, beginning January 1, 2018, reduced the federal statutory rate from 35% to 21% and extended bonus depreciation provisions. In addition, the TCJA prescribes the application of net operating loss carryforwards generated in 2018 and beyond will be limited, 100% asset expensing will be allowed through 2022 and begin to phase out in 2023, and the amount of interest expense we are able to deduct may also be limited in future years. We completed our analysis of the TCJA in 2018 consistent with the guidance of Staff Accounting Bulletin 118 and any adjustments during the measurement period were included in net earnings from continuing operations as an adjustment to income tax expense. As such, in the fourth quarter of 2018, we recorded additional tax expense of $17.6 million resulting from the IRS interpretative guidance of TCJA. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: Unrecognized Tax Benefits Balance—December 29, 2018 $ 22,663 Additions based on tax position in 2018 18,885 Balance—December 28, 2019 $ 41,548 Reductions based on new regulations (41,548) Balance—January 2, 2021 $ — At January 2, 2021, December 28, 2019 and December 29, 2018 there was $0.0 million, $41.5 million and $22.7 million, respectively, of unrecognized tax benefits that if recognized would affect the annual effective tax rate. We did not recognize interest or penalties related to this amount as it is offset by other attributes. Our net operating loss carryforward deferred tax assets begin to expire in 2030 and are expected to reverse before expiration. Therefore, we have not given consideration to any potential tax planning strategies as a source of future taxable income to monetize those net operating loss carryforwards. The Company will continue to monitor facts and circumstances, including our analysis of other sources of taxable income, in the reassessment of the likelihood that the tax benefit of our deferred tax assets will be realized. As of January 2, 2021, Summit Inc. had federal net operating loss carryforwards of $917 million, a portion of which expire between 2030 and 2038. As of January 2, 2021, $497 million of our federal net operating losses were under the terms of our TRA. As of January 2, 2021 and December 28, 2019, Summit Inc. had a valuation allowance on net deferred tax assets of $1.7 million and $1.7 million, respectively, where realization of our net operating losses are not more likely than not. 2020 2019 Valuation Allowance: Beginning balance $ (1,675) $ (19,366) Current year decreases (increases) from operations — 17,691 Ending balance $ (1,675) $ (1,675) Tax Receivable Agreement — During 2015, the Company entered into a TRA with the holders of LP Units and certain other pre-initial public offering owners (“Investor Entities”) that provides for the payment by Summit Inc. to exchanging holders of LP Units of 85% of the benefits, if any, that Summit Inc. actually realizes (or, under certain circumstances such as an early termination of the TRA, is deemed to realize) as a result of increases in the tax basis of tangible and intangible assets of Summit Holdings and certain other tax benefits related to entering into the TRA, including tax benefits attributable to payments under the TRA. When LP Units are exchanged for an equal number of newly-issued shares of Summit Inc.’s Class A common stock, these exchanges result in new deferred tax assets. Using tax rates in effect as of each year end, $2.4 million and $1.1 million of deferred tax assets were created during the years ended January 2, 2021 and December 28, 2019, respectively, when LP Units were exchanged for shares of Class A common stock. Each year, we update our estimate as to when TRA payments will be made. As noted above, when payments are made under the TRA, a portion of the payment made will be characterized as imputed interest under IRS regulations. The TCJA enacted in late 2017 contained provisions whereby interest expense deductions may be limited, and the IRS issued proposed regulations in late 2018 around the deductibility of interest expense. Under our forecast prepared at the end of 2018, we expected the amount of imputed interest based on future TRA payments would result in interest expense deductions being limited, and therefore we would not benefit from that deduction. However, based on the updated forecast model at the end of 2019, which updated our forecast of the timing of TRA payments, we believe that our interest expense deductions will not be limited under the proposed regulations. We also updated our estimate of the state income tax rate that will be in effect at the date the TRA payments are made. As a result of our updated state income tax rate, and the imputed interest limitation noted above, we have decreased our TRA liability $7.6 million and increased by $16.2 million as of January 2, 2021 and December 28, 2019, respectively. Our TRA liability as of January 2, 2021 and December 28, 2019 was $321.7 million and $327.0 million, respectively. Tax Distributions – The holders of Summit Holdings’ LP Units, including Summit Inc., incur U.S. federal, state and local income taxes on their share of any taxable income of Summit Holdings. The limited partnership agreement of Summit Holdings provides for pro rata cash distributions (“tax distributions”) to the holders of the LP Units in an amount generally calculated to provide each holder of LP Units with sufficient cash to cover its tax liability in respect of the LP Units. In general, these tax distributions are computed based on Summit Holdings’ estimated taxable income allocated to Summit Inc. multiplied by an assumed tax rate equal to the highest effective marginal combined U.S. federal, state and local income tax rate applicable to a corporate resident in New York, New York. For the years ended January 2, 2021 and December 28, 2019, Summit Holdings did not pay any tax distributions and paid tax distributions totaling $0.1 million, respectively, to holders of its LP Units, other than Summit Inc. C Corporation Subsidiaries — The effective income tax rate for the C corporations differ from the statutory federal rate primarily due to (1) tax depletion expense (benefit) in excess of the expense recorded under U.S. GAAP, (2) state income taxes and the effect of graduated tax rates, (3) various other items such as limitations on meals and entertainment and other costs and (4) unrecognized tax benefits. The effective income tax rate for the Canadian subsidiary is not significantly different from its historical effective tax rate. No material interest or penalties were recognized in income tax expense during the years ended January 2, 2021, December 28, 2019 or December 29, 2018. Tax years from 2014 to 2018 remain open and subject to audit by federal, Canadian, and state tax authorities.
Summit Materials, LLC
Income Taxes [Line Items]
Income Taxes	Income Taxes Summit LLC is a limited liability company and passes its tax attributes for federal and state tax purposes to its member and is generally not subject to federal or state income tax. However, certain subsidiaries, or subsidiary groups, file federal, state, and Canadian income tax returns due to their status as C corporations or laws within that jurisdiction. The provision for income taxes is primarily composed of federal, state and local income taxes for the subsidiary entities that have C corporation status. For the years ended January 2, 2021, December 28, 2019 and December 29, 2018, income taxes consisted of the following: 2020 2019 2018 Provision for income taxes: Current $ 3,827 $ 69 $ 463 Deferred (2,764) 6,316 9,810 Income tax expense (benefit) $ 1,063 $ 6,385 $ 10,273 The effective tax rate on pre-tax income differs from the U.S. statutory rate of 21% for 2020, 2019 and 2018, respectively, due to the following: 2020 2019 2018 Income tax expense (benefit) at federal statutory tax rate $ 25,577 $ 19,947 $ 15,563 Less: Income tax benefit at federal statutory tax rate for LLC entities (17,647) (15,387) (13,863) State and local income taxes 2,073 1,680 1,614 Permanent differences 2,479 13 (1,194) Effective tax rate change 681 (725) (1,148) Unrecognized tax benefits (11,525) 5,038 6,487 Valuation allowance — (2,478) 2,586 Other (575) (1,703) 228 Income tax benefit $ 1,063 $ 6,385 $ 10,273 The following table summarizes the components of the net deferred income tax asset (liability) as January 2, 2021 and December 28, 2019: 2020 2019 Deferred tax (liabilities) assets: Accelerated depreciation $ (70,588) $ (60,216) Net operating loss 26,929 18,036 Investment in limited partnership (18,931) (17,686) Net intangible assets (3,264) (2,554) Mining reclamation reserve 1,652 723 Working capital (e.g., accrued compensation, prepaid assets) 1,590 1,366 Interest expense limitation carryforward — 2,691 Net deferred tax liabilities (62,612) (57,640) Less valuation allowance (1,675) (1,675) Net deferred tax liability $ (64,287) $ (59,315) The net deferred income tax liability as of January 2, 2021 and December 28, 2019, are included in other noncurrent liabilities on the consolidated balance sheets. As of January 2, 2021, Summit LLC had federal net operating loss carryforwards of $120.3 million, which expire between 2030 and 2037. Valuation Allowance —The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible (including the effect of available carryback and carryforward periods) and tax-planning strategies. The deferred income tax asset related to net operating losses resides with two separate tax paying subsidiaries (or subsidiary groups) of Summit LLC. These tax payers have historically generated taxable income and forecast to continue generating taxable income; however, the use of a portion of the net operating may be limited. 2020 2019 Valuation Allowance: Beginning balance $ (1,675) $ (4,261) Loss carryforwards — — Current year decreases (increases) from operations — 2,586 Release of valuation allowance and other — — Ending balance $ (1,675) $ (1,675) On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (“TCJA”) was enacted. Among other things, the TCJA, beginning January 1, 2018, reduced the federal statutory rate from 35% to 21% and extended bonus depreciation provisions. In addition, the TCJA prescribes the application of net operating loss carryforwards generated in 2018 and beyond will be limited, 100% asset expensing will be allowed through 2022 and begin to phase out in 2023, and the amount of interest expense we are able deduct may also be limited in future years. The TCJA contains many provisions which continue to be clarified through new regulations. As permitted by Staff Accounting Bulletin 118 issued by the SEC on December 22, 2017, we completed our accounting of the impacts of the TCJA. We have completed our analysis within 2018 consistent with the guidance of SAB 118 and any adjustments during the measurement period have been included in net earnings from continuing operations as an adjustment to income tax expense. As such, in the fourth quarter of 2018, the Company recorded additional tax expense of $2.6 million resulting from the IRS interpretative guidance of TCJA. As of January 2, 2021 and December 28, 2019, a $1.7 million and $1.7 million, respectively, valuation allowance has been recorded on net deferred tax assets where realization of our net operating losses are not more likely than not. The Company has recognized a reserve against the deferred tax assets for unrecognized tax benefits in the amount of $0.0 million and $11.6 million as of January 2, 2021 and December 28, 2019, respectively. The Company records interest and penalties as a component of the income tax provision. No material interest or penalties were recognized in income tax expense during the years ended January 2, 2021 and December 28, 2019. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: Unrealized Tax Benefits Balance—December 29, 2018 $ 6,487 Additions based on tax position in 2018 5,132 Balance—December 28, 2019 $ 11,619 Reductions based on new regulations (11,619) Balance—January 2, 2021 $ — Tax years from 2014 to 2019 remain open and subject to audit by federal, Canadian, and state tax authorities. No income tax expense or benefit was recognized in other comprehensive loss in 2019, 2018 or 2017. Tax Distributions –

Earnings Per Share

Earnings Per Share	12 Months Ended
	Jan. 02, 2021
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per share is computed by dividing net earnings by the weighted average common shares outstanding and diluted net earnings is computed by dividing net earnings, adjusted for changes in the earnings allocated to Summit Inc. as a result of the assumed conversion of LP Units, by the weighted-average common shares outstanding assuming dilution. The following table shows the calculation of basic income per share: 2020 2019 2018 Net income attributable to Summit Inc. $ 137,967 $ 59,066 $ 33,906 Weighted average shares of Class A stock outstanding Add: Nonvested restricted stock awards of retirement eligible shares 212,443 — — Add: Weighted average shares of Class A stock outstanding 114,014,749 112,204,067 111,380,175 Weighted average basic shares outstanding 114,227,192 112,204,067 111,380,175 Basic earnings per share $ 1.21 $ 0.53 $ 0.30 Diluted net income attributable to Summit Inc. $ 137,967 $ 59,066 $ 33,906 Weighted average shares of Class A stock outstanding 114,014,749 112,204,067 111,380,175 Add: stock options 3,390 87,290 282,329 Add: warrants — 4,206 25,049 Add: restricted stock units 520,871 342,620 459,280 Add: performance stock units 92,758 46,535 169,813 Weighted average dilutive shares outstanding 114,631,768 112,684,718 112,316,646 Diluted earnings per share $ 1.20 $ 0.52 $ 0.30 Excluded from the above calculations were the shares noted below as they were antidilutive: 2020 2019 2018 Antidilutive shares: LP Units 3,060,248 3,372,706 3,512,669 Warrants 100,037 — —

Stockholder's Equity_Members' I

Stockholder's Equity/Members' Interest	12 Months Ended
	Jan. 02, 2021
Schedule of Capitalization, Equity [Line Items]
Stockholder's Equity	Stockholders’ Equity Our capital stock consists of 1.0 billion shares of $0.01 par value Class A common stock authorized, of which 114,390,595 shares were issued and outstanding as of January 2, 2021. We also have authorized 250 million shares of $0.01 par value Class B common stock, of which 99 shares were issued and outstanding as of January 2, 2021. The Class B common stock entitles holders thereof, who are also holders of LP Units, with a number of votes that is equal to the number of LP Units they hold. The Class B common stock does not participate in dividends and does not have any liquidation rights. From time to time, limited partners of Summit Holdings exchange their LP Units for shares of Class A common stock of Summit Inc. The following table summarizes the changes in our ownership of Summit Holdings: Summit Inc. Shares (Class A) LP Units Total Summit Inc. Ownership Percentage Balance — December 29, 2018 111,658,927 3,435,518 115,094,445 97.0 % Exchanges during period 185,861 (185,861) — Stock option exercises 1,065,446 — 1,065,446 Other equity transactions 399,151 — 399,151 Balance — December 28, 2019 113,309,385 3,249,657 116,559,042 97.2 % Exchanges during period 376,487 (376,487) — Stock option exercises 54,517 — 54,517 Other equity transactions 650,206 — 650,206 Balance — January 2, 2021 114,390,595 2,873,170 117,263,765 97.5 % Accumulated other comprehensive income (loss) - The changes in each component of accumulated other comprehensive income (loss) consisted of the following: Accumulated Foreign currency other Change in translation Cash flow hedge comprehensive retirement plans adjustments adjustments income (loss) Balance — December 29, 2018 $ 3,573 $ (2,147) $ 1,255 $ 2,681 Postretirement liability adjustment, net of tax (1,402) — — (1,402) Foreign currency translation adjustment, net of tax — 3,424 — 3,424 Income on cash flow hedges, net of tax — — (1,255) (1,255) Balance — December 28, 2019 $ 2,171 $ 1,277 $ — $ 3,448 Postretirement liability adjustment, net of tax (1,638) — — (1,638) Foreign currency translation adjustment, net of tax — 3,393 — 3,393 Balance — January 2, 2021 $ 533 $ 4,670 $ — $ 5,203
Summit Materials, LLC
Schedule of Capitalization, Equity [Line Items]
Members' Interest	Members’ Interest Summit LLC is a wholly owned indirect subsidiary of Summit Holdings, whose primary owner is Summit Inc. Summit Inc. was formed as a Delaware corporation on September 23, 2014. Its sole material asset is a controlling equity interest in Summit Holdings. Pursuant to a reorganization into a holding company structure (the “Reorganization”) in connection with Summit Inc.’s March 2015 initial public offering, Summit Inc. became a holding corporation operating and controlling all of the business and affairs of Summit Holdings and its subsidiaries, including Summit LLC. Accumulated other comprehensive income (loss) - The changes in each component of accumulated other comprehensive income (loss) consisted of the following: Accumulated Foreign currency other Change in translation Cash flow hedge comprehensive retirement plans adjustments adjustments income (loss) Balance — December 29, 2018 $ (4,392) $ (19,370) $ 146 $ (23,616) Postretirement liability adjustment (1,925) — — (1,925) Foreign currency translation adjustment — 4,716 — 4,716 Income on cash flow hedges — — (146) (146) Balance — December 28, 2019 $ (6,317) $ (14,654) $ — $ (20,971) Postretirement liability adjustment (2,229) — — (2,229) Foreign currency translation adjustment — 4,617 — 4,617 Balance — January 2, 2021 $ (8,546) $ (10,037) $ — $ (18,583)

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Jan. 02, 2021
Schedule Of Cash Flow Supplemental [Line Items]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Supplemental cash flow information for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was as follows: 2020 2019 2018 Cash payments: Interest $ 99,551 $ 104,614 $ 103,250 Payments (refunds) for income taxes, net 1,754 (919) 3,340 Operating cash payments on operating leases 10,452 10,618 N/A Operating cash payments on finance leases 3,132 3,051 N/A Finance cash payments on finance leases 14,408 13,164 N/A Non cash financing activities: Right of use assets obtained in exchange for operating lease obligations $ 4,849 $ 5,842 N/A Right of use assets obtained in exchange for finance leases obligations 18,016 23,965 N/A Exchange of LP Units to shares of Class A common stock 8,227 3,847 7,499
Summit Materials, LLC
Schedule Of Cash Flow Supplemental [Line Items]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Supplemental cash flow information for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was as follows: 2020 2019 2018 Cash payments: Interest $ 99,551 $ 104,614 $ 103,250 Payments (refunds) for income taxes, net 1,754 (919) 3,340 Operating cash payments on operating leases 10,452 10,618 N/A Operating cash payments on finance leases 3,132 3,051 N/A Finance cash payments on finance leases 14,408 13,164 N/A Non cash financing activities: Right of use assets obtained in exchange for operating lease obligations $ 4,849 $ 5,842 N/A Right of use assets obtained in exchange for finance leases obligations 18,016 23,965 N/A

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Jan. 02, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	Stock-Based Compensation Prior to the IPO and related Reorganization, the capital structure of Summit Holdings consisted of six different classes of limited partnership units, each of which was subject to unique distribution rights. In connection with the IPO and the related Reorganization, the limited partnership agreement of Summit Holdings was amended and restated to, among other things, modify its capital structure by creating LP Units. Holders of the LP Units periodically exchange their LP Units for shares of Class A common Stock of Summit Inc. In the first quarter of 2018, the Board of Directors vested the time-vesting units outstanding and we recognized the remaining $1.0 million of stock based compensation related to these LP units. Omnibus Incentive Plan In 2015, our Board of Directors and stockholders adopted the Summit Materials, Inc. 2015 Omnibus Incentive Plan (the "Plan"), which allows for grants of equity-based awards in the form of stock options, stock appreciation rights, restricted stock and restricted stock units, performance units, and other stock-based awards. The Plan authorizes the issuance of up to 13,500,000 shares of Class A common stock in the form of restricted stock units and stock options, of which 4.3 million shares were available for future grants as of January 2, 2021. Restricted Stock Restricted Stock with Service-Based Vesting—Under the Plan, the Compensation Committee of the Board of Directors (the “Compensation Committee”) has granted restricted stock to members of the Board of Directors, executive officers and other key employees. These awards contain service conditions associated with continued employment or service. The terms of the restricted stock provide voting and regular dividend rights to holders of the awards. Upon vesting, the restrictions on the restricted stock lapse and the shares are considered issued and outstanding for accounting purposes. In each of 2020, 2019 and 2018, the Compensation Committee granted restricted stock to executives and key employees under the Plan as part of our annual equity award program, which vest over a two three Further, in each of 2020, 2019 and 2018, the Compensation Committee granted 42,736, 65,144 and 38,232 shares, respectively, to non-employee members of the Board of Directors for their annual service as directors. These restricted stock grants vest over a one year period. In measuring compensation expense associated with the grant of restricted stock, we use the fair value of the award, determined as the closing stock price for our Class A common stock on the date of grant. Compensation expense is recorded monthly over the vesting period of the award. Restricted stock with Service- and Market-Condition-Based Vesting—In 2020, 2019 and 2018, the Compensation Committee granted restricted stock to certain members of our executive team as part of their annual compensation package. The restricted stock vests at the end of a three Compensation expense is recorded monthly over the vesting period of the awards. The following table summarizes information for the equity awards granted in 2020: Options Restricted Stock Units Performance Stock Units Warrants Weighted Weighted Weighted Weighted average grant- Number of average grant- Number of average grant- average grant- Number of date fair value restricted date fair value performance date fair value Number of date fair value options per unit stock units per unit stock units per unit warrants per unit Beginning balance—December 28, 2019 2,128,107 $ 9.08 1,556,636 $ 20.29 390,645 $ 31.08 100,037 $ 18.00 Granted — — 1,379,943 18.10 199,946 23.43 — — Forfeited/ Canceled (35,117) 12.30 (154,283) 19.12 (112,416) 26.54 — — Exercised (54,517) 10.10 — — — — — — Vested — — (647,345) 21.28 (49,300) 32 — — Balance—January 2, 2021 2,038,473 $ 9.16 2,134,951 $ 18.64 428,875 $ 28.64 100,037 $ 18.00 The fair value of the time-vesting options granted was estimated as of the grant date using the Black-Scholes-Merton model, which requires the input of subjective assumptions, including the expected volatility and the expected term. The fair value of the performance stock units granted was estimated as of the grant date using Monte Carlo simulations, which requires the input of subjective assumptions, including the expected volatility and the expected term. No options to purchase common stock were granted in 2020, 2019 and 2018. The risk-free rate is based on the yield at the date of grant of a U.S. Treasury security with a maturity period approximating the expected term. As Summit Holdings has not historically and does not plan to issue regular dividends, a dividend yield of zero was used. The volatility assumption is based on reported data of a peer group of publicly traded companies for which historical information was available adjusted for the Company’s capital structure. The expected term is based on expectations about future exercises and represents the period of time that the units granted are expected to be outstanding. Compensation expense for time-vesting interests granted is based on the grant date fair value. The Company recognizes compensation costs on a straight-line basis over the service period, which is generally the vesting period of the award. Forfeitures are recognized as they occur. Share-based compensation expense, which is recognized in general and administrative expenses, totaled $28.9 million, $20.4 million and $25.4 million in the years ended January 2, 2021, December 28, 2019 and December 29, 2018, respectively. As of January 2, 2021, unrecognized compensation cost totaled $22.0 million. The weighted average remaining contractual term over which the unrecognized compensation cost is to be recognized is 1.7 years as of year-end 2020. As of January 2, 2021, the intrinsic value of outstanding options, restricted stock units and performance stock units was $3.8 million, $42.9 million and $8.6 million, respectively, and the remaining contractual term was 3.3 years, 1.0 year and 1.3 years, respectively. The weighted average strike price of stock options outstanding as of January 2, 2021 was $18.75 per share. The intrinsic value of 2.0 million exercisable stock options as of January 2, 2021 was $3.8 million with a weighted average strike price of $18.75 and a weighted average remaining contractual period of 3.3 years.
Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	Stock-Based Compensation Prior to the IPO and related Reorganization, the capital structure of Summit Holdings consisted of six different classes of limited partnership units, each of which was subject to unique distribution rights. In connection with the IPO and the related Reorganization, the limited partnership agreement of Summit Holdings was amended and restated to, among other things, modify its capital structure by creating LP Units. Holders of the LP Units periodically exchange their LP Units for shares of Class A common Stock of Summit Inc. In the first quarter of 2018, the Board of Directors vested the time-vesting units outstanding and we recognized the remaining $1.0 million of stock based compensation related to these LP units. Omnibus Incentive Plan In 2015, our Board of Directors and stockholders adopted the Summit Materials, Inc. 2015 Omnibus Incentive Plan (the "Plan"), which allows for grants of equity-based awards in the form of stock options, stock appreciation rights, restricted stock and restricted stock units, performance units, and other stock-based awards. The Plan authorizes the issuance of up to 13,500,000 shares of Class A common stock in the form of restricted stock units and stock options, of which 4.3 million shares were available for future grants as of January 2, 2021. Restricted Stock Restricted Stock with Service-Based Vesting —Under the Plan, the Compensation Committee of the Board of Directors (the “Compensation Committee”) has granted restricted stock to members of the Board of Directors, executive officers and other key employees. These awards contain service conditions associated with continued employment or service. The terms of the restricted stock provide voting and regular dividend rights to holders of the awards. Upon vesting, the restrictions on the restricted stock lapse and the shares are considered issued and outstanding for accounting purposes. In each of 2020, 2019 and 2018, the Compensation Committee granted restricted stock to executives and key employees under the Plan as part of our annual equity award program, which vest over a two three Further, in each of 2020, 2019 and 2018, the Compensation Committee granted 42,736, 65,144 and 38,232 shares, respectively, to non-employee members of the Board of Directors for their annual service as directors. These restricted stock grants vest over a one year period. In measuring compensation expense associated with the grant of restricted stock, we use the fair value of the award, determined as the closing stock price for our Class A common stock on the date of grant. Compensation expense is recorded monthly over the vesting period of the award. Restricted stock with Service- and Market-Condition-Based Vesting —In 2020, 2019 and 2018, the Compensation Committee granted restricted stock to certain members of our executive team as part of their annual compensation package. The restricted stock vests at the end of a three Compensation expense is recorded monthly over the vesting period of the awards. The following table summarizes information for the equity awards granted in 2020: Options Restricted Stock Units Performance Stock Units Warrants Weighted Weighted Weighted Weighted average grant- Number of average grant- Number of average grant- average grant- Number of date fair value restricted date fair value performance date fair value Number of date fair value options per unit stock units per unit stock units per unit warrants per unit Beginning balance—December 28, 2019 2,128,107 $ 9.08 1,556,636 $ 20.29 390,645 $ 31.08 100,037 $ 18.00 Granted — — 1,379,943 18.10 199,946 23.43 — — Forfeited/ Canceled (35,117) 12.30 (154,283) 19.12 (112,416) 26.54 — — Exercised (54,517) 10.10 — — — — — — Vested — — (647,345) 21.28 (49,300) 32 — — Balance—January 2, 2021 2,038,473 $ 9.16 2,134,951 $ 18.64 428,875 $ 28.64 100,037 $ 18.00 The fair value of the time-vesting options granted was estimated as of the grant date using the Black-Scholes-Merton model, which requires the input of subjective assumptions, including the expected volatility and the expected term. The fair value of the performance stock units granted was estimated as of the grant date using Monte Carlo simulations, which requires the input of subjective assumptions, including the expected volatility and the expected term. No options to purchase common stock were granted in 2020, 2019 and 2018. The risk-free rate is based on the yield at the date of grant of a U.S. Treasury security with a maturity period approximating the expected term. As Summit Holdings has not historically and does not plan to issue regular dividends, a dividend yield of zero was used. The volatility assumption is based on reported data of a peer group of publicly traded companies for which historical information was available adjusted for the Company’s capital structure. The expected term is based on expectations about future exercises and represents the period of time that the units granted are expected to be outstanding. Compensation expense for time-vesting interests granted is based on the grant date fair value. The Company recognizes compensation costs on a straight-line basis over the service period, which is generally the vesting period of the award. Forfeitures are recognized as they occur. Share-based compensation expense, which is recognized in general and administrative expenses, totaled $28.9 million, $20.4 million and $25.4 million in the years ended January 2, 2021, December 28, 2019 and December 29, 2018, respectively. As of January 2, 2021, unrecognized compensation cost totaled $22.0 million. The weighted average remaining contractual term over which the unrecognized compensation cost is to be recognized is 1.7 years as of year-end 2020. As of January 2, 2021, the intrinsic value of outstanding options, restricted stock units and performance stock units was $3.8 million, $42.9 million and $8.6 million, respectively, and the remaining contractual term was 3.3 years, 1.0 year and 1.3 years, respectively. The weighted average strike price of stock options outstanding as of January 2, 2021 was $18.75 per share. The intrinsic value of 2.0 million exercisable stock options as of January 2, 2021 was $3.8 million with a weighted average strike price of $18.75 and a weighted average remaining contractual period of 3.3 years.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Jan. 02, 2021
Defined Benefit Plan Disclosure [Line Items]
Employee Benefit Plans	Employee Benefit Plans Defined Contribution Plan —The Company sponsors employee 401(k) savings plans for its employees, including certain union employees. The plans provide for various required and discretionary Company matches of employees’ eligible compensation contributed to the plans. The expense for the defined contribution plans was $12.1 million, $11.7 million and $11.2 million for the years ended January 2, 2021, December 28, 2019 and December 29, 2018, respectively. Defined Benefit and Other Postretirement Benefits Plans —The Company’s subsidiary, Continental Cement, sponsors two noncontributory defined benefit pension plans for hourly and salaried employees. The plans are closed to new participants and benefits are frozen. As a result of the collective bargaining unit negotiations in 2017, the hourly defined benefit pension plan was amended to stop future benefit accruals for the Davenport employees effective December 31, 2017. Pension benefits for eligible hourly employees are based on a monthly pension factor for each year of credited service. Pension benefits for eligible salaried employees are generally based on years of service and average eligible compensation. Continental Cement also sponsors two unfunded healthcare and life insurance benefits plans for certain eligible retired employees. Effective January 1, 2014, the plan covering employees of the Hannibal, Missouri location was amended to eliminate all future retiree health and life coverage for current employees. During 2015, Continental Cement adopted one new unfunded healthcare plan to provide benefits prior to Medicare eligibility for certain hourly employees of the Davenport, Iowa location. As a result of the collective bargaining unit negotiations in 2017, hourly Davenport employees hired on or after January 1, 2018 are no longer eligible for retiree medical benefits. The funded status of the pension and other postretirement benefit plans is recognized in the consolidated balance sheets as the difference between the fair value of plan assets and the benefit obligations. For defined benefit pension plans, the benefit obligation is the projected benefit obligation (“PBO”) and for the healthcare and life insurance benefits plans, the benefit obligation is the accumulated postretirement benefit obligation (“APBO”). The PBO represents the actuarial present value of benefits expected to be paid upon retirement based on estimated future compensation levels. However, since the plans’ participants are not subject to future compensation increases, the plans’ PBO equals the accumulated benefit obligation (“ABO”). The APBO represents the actuarial present value of postretirement benefits attributed to employee services already rendered. The fair value of plan assets represents the current market value of assets held by an irrevocable trust fund for the sole benefit of participants. The measurement of the benefit obligations is based on the Company’s estimates and actuarial valuations. These valuations reflect the terms of the plan and use participant-specific information, such as compensation, age and years of service, as well as certain assumptions that require significant judgment, including estimates of discount rates, expected return on plan assets, rate of compensation increases, interest-crediting rates and mortality rates. The Company uses December 31 as the measurement date for its defined benefit pension and other postretirement benefit plans. Obligations and Funded Status —The following information is as of January 2, 2021 and December 28, 2019 and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. Change in benefit obligations: Beginning of period $ 26,181 $ 9,090 $ 24,203 $ 9,203 Service cost 71 176 60 166 Interest cost 733 242 928 321 Actuarial (gain) loss 2,425 676 2,571 165 Benefits paid (1,583) (955) (1,581) (765) End of period $ 27,827 $ 9,229 $ 26,181 $ 9,090 Change in fair value of plan assets: Beginning of period $ 18,242 $ — $ 17,449 $ — Actual return on plan assets 1,916 — 2,055 — Employer contributions 483 955 319 765 Benefits paid (1,583) (955) (1,581) (765) End of period $ 19,058 $ — $ 18,242 $ — Funded status of plans $ (8,769) $ (9,229) $ (7,939) $ (9,090) Current liabilities $ — $ (636) $ — $ (653) Noncurrent liabilities (8,769) (8,593) (7,939) (8,437) Liability recognized $ (8,769) $ (9,229) $ (7,939) $ (9,090) Amounts recognized in accumulated other comprehensive income: Net actuarial (gain) loss $ 10,689 $ 2,707 $ 9,286 $ 2,121 Prior service cost — (1,690) — (1,931) Total amount recognized $ 10,689 $ 1,017 $ 9,286 $ 190 The amount recognized in accumulated other comprehensive income (“AOCI”) is the actuarial loss (credit) and prior service cost, which has not yet been recognized in periodic benefit cost. 2020 2019 2018 Pension Healthcare Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. benefits & Life Ins. Amounts recognized in other comprehensive (income) loss: Net actuarial loss (gain) $ 1,728 $ 675 $ 1,760 $ 165 $ (1,300) $ (172) Amortization of prior year service cost — 241 — 241 — 241 Amortization of gain (326) (89) (202) (39) (312) (118) Total amount recognized $ 1,402 $ 827 $ 1,558 $ 367 $ (1,612) $ (49) Components of net periodic benefit cost: Service cost $ 71 $ 176 $ 60 $ 166 $ 67 $ 170 Interest cost 733 242 928 321 898 317 Amortization of gain 326 89 202 39 312 118 Expected return on plan assets (1,221) — (1,244) — (1,284) — Amortization of prior service credit — (241) — (241) — (241) Net periodic (expense) benefit cost $ (91) $ 266 $ (54) $ 285 $ (7) $ 364 Assumptions— Weighted-average assumptions used to determine the benefit obligations as of year-end 2020 and 2019 are: 2020 2019 Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 1.84% - 2.14% 1.80% - 1.82% 2.78% - 2.96% 2.73% - 2.79% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A Weighted-average assumptions used to determine net periodic benefit cost for years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Healthcare Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 2.78% - 2.96% 2.73% - 2.79% 3.90% - 4.02% 3.87% - 3.91% 3.23% - 3.37% 3.20% - 3.25% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A 7.00% N/A The expected long-term return on plan assets is based upon the Plans’ consideration of historical and forward-looking returns and the Company’s estimation of what a portfolio, with the target allocation described below, will earn over a long-term horizon. The discount rate is derived using the FTSE Pension Discount Curve. Assumed health care cost trend rates were 8.0% as of year-end 2020 and 2019, grading to an ultimate trend rate of 4.5% in 2034 and 2033. Assumed health care cost trend rates have a significant effect on the amounts reported for the Company’s healthcare and life insurance benefits plans. Plan Assets —The defined benefit pension plans’ (the “Plans”) investment strategy is to minimize investment risk while generating acceptable returns. The Plans currently invest a relatively high proportion of the plan assets in fixed income securities, while the remainder is invested in equity securities, cash reserves and precious metals. The equity securities are diversified into funds with growth and value investment strategies. The target allocation for plan assets is as follows: equity securities—30%; fixed income securities—63%; cash reserves—5%; and precious metals—2%. The Plans’ current investment allocations are within the tolerance of the target allocation. The Company had no Level 3 investments as of or for the years ended January 2, 2021 and December 28, 2019. At year-end 2020 and 2019, the Plans’ assets were invested predominantly in fixed-income securities and publicly traded equities, but may invest in other asset classes in the future subject to the parameters of the investment policy. The Plans’ investments in fixed-income assets include U.S. Treasury and U.S. agency securities and corporate bonds. The Plans’ investments in equity assets include U.S. and international securities and equity funds. The Company estimates the fair value of the Plans’ assets using various valuation techniques and, to the extent available, quoted market prices in active markets or observable market inputs. The descriptions and fair value methodologies for the Plans’ assets are as follows: Fixed Income Securities —Corporate and government bonds are classified as Level 2 assets, as they are either valued at quoted market prices from observable pricing sources at the reporting date or valued based upon comparable securities with similar yields and credit ratings. Equity Securities —Equity securities are valued at the closing market price reported on a U.S. exchange where the security is actively traded and are therefore classified as Level 1 assets. Cash —The carrying amounts of cash approximate fair value due to the short-term maturity. Precious Metals— Precious metals are valued at the closing market price reported on a U.S. exchange where the security is actively traded and are therefore classified as Level 1 assets. The fair value of the Plans’ assets by asset class and fair value hierarchy level as of January 2, 2021 and December 28, 2019 are as follows: 2020 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 3,294 $ 3,294 $ — Intermediate—corporate 3,218 — 3,218 Short-term—government 705 705 — Short-term—corporate 448 — 448 International 1,086 — 1,086 Equity securities: U.S. Large cap value 1,516 1,516 — U.S. Large cap growth 1,483 1,483 — U.S. Mid cap value 631 631 — U.S. Mid cap growth 619 619 — U.S. Small cap value 663 663 — U.S. Small cap growth 650 650 — International 1,227 407 820 Emerging Markets 409 409 — Commodities Broad Basket 1,002 182 820 Cash 2,107 2,107 — Total $ 19,058 $ 12,666 $ 6,392 2019 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 2,482 $ 2,482 $ — Intermediate—corporate 1,066 — 1,066 Short-term—government 1,387 1,387 — Short-term—corporate 3,173 — 3,173 International 1,387 — 1,387 Equity securities: U.S. Large cap value 1,225 1,225 — U.S. Large cap growth 1,167 1,167 — U.S. Mid cap value 581 581 — U.S. Mid cap growth 578 578 — U.S. Small cap value 583 583 — U.S. Small cap growth 593 593 — Managed Futures 340 — 340 International 1,174 386 788 Emerging Markets 394 394 — Commodities Broad Basket 1,118 362 756 Cash 994 994 — Total $ 18,242 $ 10,732 $ 7,510 Cash Flows —The Company expects to contribute approximately $1.2 million and $0.6 million in 2021 to its pension plans and to its healthcare and life insurance benefits plans, respectively. The estimated benefit payments for each of the next five years and the five-year period thereafter are as follows: Pension Healthcare and Life benefits Insurance Benefits 2021 $ 1,692 $ 636 2022 1,693 630 2023 1,696 617 2024 1,655 619 2025 1,613 627 2026 - 2030 7,597 3,139 Multiemployer Pension Plans — In 2018, the Company acquired Buildex, LLC and assumed its obligation to contribute to a number of multiemployer defined benefit pension plans under the terms of collective-bargaining agreements that cover its union-represented employees. The risks of participating in multiemployer pension plans are different from single-employer plans. Assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers. If a participating employer ceases contributing to the plan, the unfunded obligations of the plan are the responsibility of the remaining participating employers. The Company's participation in these plans for the annual period ended December 31, 2020, is outlined in the table below. The ''EIN/Pension Plan Number" column provides the Employer Identification Number (EIN) and the three-digit plan number, if applicable. Unless otherwise noted, the most recent Pension Protection Act (PPA) zone status available in 2020 and 2019 is for the plan 's year end at December 31, 2020, and December 31, 2019, respectively. The zone status is based on information the Company received from the plan and is certified by the plan's actuary. Among other factors, plans in the red zone are generally less than 65% funded, plans in the yellow zone are less than 80% funded and plans in the green zone are at least 80% funded. The "FIP/RP Status Pending/Implemented" column indicates plans for which a financial improvement plan (FIP) or a rehabilitation plan (RP) is either pending or has been implemented. The "Surcharge Imposed" column indicates whether a surcharge has been imposed on contributions to the plan. The last column lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject. There have been no significant changes that affect the comparability of 2020 and 2019 contributions. Expiration Date of Pension Protection Act FIP/RP Status Contributions of Company Collective- Pension EIN/ Pension Zone Status Pending/ ($ in thousands) Surcharge Bargaining Trust Fund Plan Number 2020 2019 Implemented 2020 2019 Imposed Agreement Construction Industry Laborers Pension Fund 43-6060737/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None $ 100 $ 112 No 3/31/2021 Operating Engineers Local 101 Pension Plan 43-6059213/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None 20 23 No 3/31/2021 Total Contributions $ 120 $ 135 The Company was not listed as providing more than 5% of the total contributions for the Operating Engineers Local 101 Pension Plan or the Construction Industry Laborers Pension Fund for the plan years 2020 and 2019 per the plans' Forms 5500. As of the date of the filing of this annual report on Form 10-K, Forms 5500 were not available for the plan year ending December 31, 2020.
Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Employee Benefit Plans	Employee Benefit Plans Defined Contribution Plan —The Company sponsors employee 401(k) savings plans for its employees, including certain union employees. The plans provide for various required and discretionary Company matches of employees’ eligible compensation contributed to the plans. The expense for the defined contribution plans was $12.1 million, $11.7 million and $11.2 million for the years ended January 2, 2021, December 28, 2019 and December 29, 2018, respectively. Defined Benefit and Other Postretirement Benefits Plans —The Company’s subsidiary, Continental Cement, sponsors two noncontributory defined benefit pension plans for hourly and salaried employees. The plans are closed to new participants and benefits are frozen. As a result of the collective bargaining unit negotiations in 2017, the hourly defined benefit pension plan was amended to stop future benefit accruals for the Davenport employees effective December 31, 2017. Pension benefits for eligible hourly employees are based on a monthly pension factor for each year of credited service. Pension benefits for eligible salaried employees are generally based on years of service and average eligible compensation. Continental Cement also sponsors two unfunded healthcare and life insurance benefits plans for certain eligible retired employees. Effective January 1, 2014, the plan covering employees of the Hannibal, Missouri location was amended to eliminate all future retiree health and life coverage for current employees. During 2015, Continental Cement adopted one new unfunded healthcare plan to provide benefits prior to Medicare eligibility for certain hourly employees of the Davenport, Iowa location. As a result of the collective bargaining unit negotiations in 2017, hourly Davenport employees hired on or after January 1, 2018 are no longer eligible for retiree medical benefits. The funded status of the pension and other postretirement benefit plans is recognized in the consolidated balance sheets as the difference between the fair value of plan assets and the benefit obligations. For defined benefit pension plans, the benefit obligation is the projected benefit obligation (“PBO”) and for the healthcare and life insurance benefits plans, the benefit obligation is the accumulated postretirement benefit obligation (“APBO”). The PBO represents the actuarial present value of benefits expected to be paid upon retirement based on estimated future compensation levels. However, since the plans’ participants are not subject to future compensation increases, the plans’ PBO equals the accumulated benefit obligation (“ABO”). The APBO represents the actuarial present value of postretirement benefits attributed to employee services already rendered. The fair value of plan assets represents the current market value of assets held by an irrevocable trust fund for the sole benefit of participants. The measurement of the benefit obligations is based on the Company’s estimates and actuarial valuations. These valuations reflect the terms of the plan and use participant-specific information, such as compensation, age and years of service, as well as certain assumptions that require significant judgment, including estimates of discount rates, expected return on plan assets, rate of compensation increases, interest-crediting rates and mortality rates. The Company uses December 31 as the measurement date for its defined benefit pension and other postretirement benefit plans. Obligations and Funded Status —The following information is as of January 2, 2021 and December 28, 2019 and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. Change in benefit obligations: Beginning of period $ 26,181 $ 9,090 $ 24,203 $ 9,203 Service cost 71 176 60 166 Interest cost 733 242 928 321 Actuarial (gain) loss 2,425 676 2,571 165 Benefits paid (1,583) (955) (1,581) (765) End of period $ 27,827 $ 9,229 $ 26,181 $ 9,090 Change in fair value of plan assets: Beginning of period $ 18,242 $ — $ 17,449 $ — Actual return on plan assets 1,916 — 2,055 — Employer contributions 483 955 319 765 Benefits paid (1,583) (955) (1,581) (765) End of period $ 19,058 $ — $ 18,242 $ — Funded status of plans $ (8,769) $ (9,229) $ (7,939) $ (9,090) Current liabilities $ — $ (636) $ — $ (653) Noncurrent liabilities (8,769) (8,593) (7,939) (8,437) Liability recognized $ (8,769) $ (9,229) $ (7,939) $ (9,090) Amounts recognized in accumulated other comprehensive income: Net actuarial (gain) loss $ 10,689 $ 2,707 $ 9,286 $ 2,121 Prior service cost — (1,690) — (1,931) Total amount recognized $ 10,689 $ 1,017 $ 9,286 $ 190 The amount recognized in accumulated other comprehensive income (“AOCI”) is the actuarial loss (credit) and prior service cost, which has not yet been recognized in periodic benefit cost. 2020 2019 2018 Pension Healthcare Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. benefits & Life Ins. Amounts recognized in other comprehensive (income) loss: Net actuarial loss (gain) $ 1,728 $ 675 $ 1,760 $ 165 $ (1,300) $ (172) Amortization of prior year service cost — 241 — 241 — 241 Amortization of gain (326) (89) (202) (39) (312) (118) Total amount recognized $ 1,402 $ 827 $ 1,558 $ 367 $ (1,612) $ (49) Components of net periodic benefit cost: Service cost $ 71 $ 176 $ 60 $ 166 $ 67 $ 170 Interest cost 733 242 928 321 898 317 Amortization of gain 326 89 202 39 312 118 Expected return on plan assets (1,221) — (1,244) — (1,284) — Amortization of prior service credit — (241) — (241) — (241) Net periodic (expense) benefit cost $ (91) $ 266 $ (54) $ 285 $ (7) $ 364 Assumptions— Weighted-average assumptions used to determine the benefit obligations as of year-end 2020 and 2019 are: 2020 2019 Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 1.84% - 2.14% 1.80% - 1.82% 2.78% - 2.96% 2.73% - 2.79% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A Weighted-average assumptions used to determine net periodic benefit cost for years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Healthcare Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 2.78% - 2.96% 2.73% - 2.79% 3.90% - 4.02% 3.87% - 3.91% 3.23% - 3.37% 3.20% - 3.25% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A 7.00% N/A The expected long-term return on plan assets is based upon the Plans’ consideration of historical and forward-looking returns and the Company’s estimation of what a portfolio, with the target allocation described below, will earn over a long-term horizon. The discount rate is derived using the FTSE Pension Discount Curve. Assumed health care cost trend rates were 8.0% as of year-end 2020 and 2019, grading to an ultimate trend rate of 4.5% in 2034 and 2033. Assumed health care cost trend rates have a significant effect on the amounts reported for the Company’s healthcare and life insurance benefits plans. Plan Assets —The defined benefit pension plans’ (the “Plans”) investment strategy is to minimize investment risk while generating acceptable returns. The Plans currently invest a relatively high proportion of the plan assets in fixed income securities, while the remainder is invested in equity securities, cash reserves and precious metals. The equity securities are diversified into funds with growth and value investment strategies. The target allocation for plan assets is as follows: equity securities—30%; fixed income securities—63%; cash reserves—5%; and precious metals—2%. The Plans’ current investment allocations are within the tolerance of the target allocation. The Company had no Level 3 investments as of or for the years ended January 2, 2021 and December 28, 2019. At year-end 2020 and 2019, the Plans’ assets were invested predominantly in fixed-income securities and publicly traded equities, but may invest in other asset classes in the future subject to the parameters of the investment policy. The Plans’ investments in fixed-income assets include U.S. Treasury and U.S. agency securities and corporate bonds. The Plans’ investments in equity assets include U.S. and international securities and equity funds. The Company estimates the fair value of the Plans’ assets using various valuation techniques and, to the extent available, quoted market prices in active markets or observable market inputs. The descriptions and fair value methodologies for the Plans’ assets are as follows: Fixed Income Securities —Corporate and government bonds are classified as Level 2 assets, as they are either valued at quoted market prices from observable pricing sources at the reporting date or valued based upon comparable securities with similar yields and credit ratings. Equity Securities —Equity securities are valued at the closing market price reported on a U.S. exchange where the security is actively traded and are therefore classified as Level 1 assets. Cash —The carrying amounts of cash approximate fair value due to the short-term maturity. Precious Metals— Precious metals are valued at the closing market price reported on a U.S. exchange where the security is actively traded and are therefore classified as Level 1 assets. The fair value of the Plans’ assets by asset class and fair value hierarchy level as of January 2, 2021 and December 28, 2019 are as follows: 2020 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 3,294 $ 3,294 $ — Intermediate—corporate 3,218 — 3,218 Short-term—government 705 705 — Short-term—corporate 448 — 448 International 1,086 — 1,086 Equity securities: U.S. Large cap value 1,516 1,516 — U.S. Large cap growth 1,483 1,483 — U.S. Mid cap value 631 631 — U.S. Mid cap growth 619 619 — U.S. Small cap value 663 663 — U.S. Small cap growth 650 650 — International 1,227 407 820 Emerging Markets 409 409 — Commodities Broad Basket 1,002 182 820 Cash 2,107 2,107 — Total $ 19,058 $ 12,666 $ 6,392 2019 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 2,482 $ 2,482 $ — Intermediate—corporate 1,066 — 1,066 Short-term—government 1,387 1,387 — Short-term—corporate 3,173 — 3,173 International 1,387 — 1,387 Equity securities: U.S. Large cap value 1,225 1,225 — U.S. Large cap growth 1,167 1,167 — U.S. Mid cap value 581 581 — U.S. Mid cap growth 578 578 — U.S. Small cap value 583 583 — U.S. Small cap growth 593 593 — Managed Futures 340 — 340 International 1,174 386 788 Emerging Markets 394 394 — Commodities Broad Basket 1,118 362 756 Cash 994 994 — Total $ 18,242 $ 10,732 $ 7,510 Cash Flows —The Company expects to contribute approximately $1.2 million and $0.6 million in 2021 to its pension plans and to its healthcare and life insurance benefits plans, respectively. The estimated benefit payments for each of the next five years and the five-year period thereafter are as follows: Pension Healthcare and Life benefits Insurance Benefits 2021 $ 1,692 $ 636 2022 1,693 630 2023 1,696 617 2024 1,655 619 2025 1,613 627 2026 - 2030 7,597 3,139 Multiemployer Pension Plans — In 2018, the Company acquired Buildex, LLC and assumed its obligation to contribute to a number of multiemployer defined benefit pension plans under the terms of collective-bargaining agreements that cover its union-represented employees. The risks of participating in multiemployer pension plans are different from single-employer plans. Assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers. If a participating employer ceases contributing to the plan, the unfunded obligations of the plan are the responsibility of the remaining participating employers. The Company's participation in these plans for the annual period ended December 31, 2020, is outlined in the table below. The ''EIN/Pension Plan Number" column provides the Employer Identification Number (EIN) and the three-digit plan number, if applicable. Unless otherwise noted, the most recent Pension Protection Act (PPA) zone status available in 2020 and 2019 is for the plan 's year end at December 31, 2020, and December 31, 2019, respectively. The zone status is based on information the Company received from the plan and is certified by the plan's actuary. Among other factors, plans in the red zone are generally less than 65% funded, plans in the yellow zone are less than 80% funded and plans in the green zone are at least 80% funded. The "FIP/RP Status Pending/Implemented" column indicates plans for which a financial improvement plan (FIP) or a rehabilitation plan (RP) is either pending or has been implemented. The "Surcharge Imposed" column indicates whether a surcharge has been imposed on contributions to the plan. The last column lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject. There have been no significant changes that affect the comparability of 2020 and 2019 contributions. Expiration Date of Pension Protection Act FIP/RP Status Contributions of Company Collective- Pension EIN/ Pension Zone Status Pending/ ($ in thousands) Surcharge Bargaining Trust Fund Plan Number 2020 2019 Implemented 2020 2019 Imposed Agreement Construction Industry Laborers Pension Fund 43-6060737/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None $ 100 $ 112 No 3/31/2021 Operating Engineers Local 101 Pension Plan 43-6059213/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None 20 23 No 3/31/2021 Total Contributions $ 120 $ 135 The Company was not listed as providing more than 5% of the total contributions for the Operating Engineers Local 101 Pension Plan or the Construction Industry Laborers Pension Fund for the plan years 2020 and 2019 per the plans' Forms 5500. As of the date of the filing of this annual report on Form 10-K, Forms 5500 were not available for the plan year ending December 31, 2020.

Accrued Mining and Landfill Rec

Accrued Mining and Landfill Reclamation	12 Months Ended
	Jan. 02, 2021
Asset Retirement Obligations [Line Items]
Accrued Mining and Landfill Reclamation	Accrued Mining and Landfill Reclamation The Company has asset retirement obligations arising from regulatory or contractual requirements to perform certain reclamation activities at the time that certain quarries and landfills are closed, which are primarily included in other noncurrent liabilities on the consolidated balance sheets. The current portion of the liabilities, $10.0 million and $7.9 million as of January 2, 2021 and December 28, 2019, respectively, is included in accrued expenses on the consolidated balance sheets. The total undiscounted anticipated costs for site reclamation as of January 2, 2021 and December 28, 2019 were $112.8 million and $97.4 million, respectively. The liabilities were initially measured at fair value and are subsequently adjusted for accretion expense, payments and changes in the amount or timing of the estimated cash flows. The corresponding asset retirement costs are capitalized as part of the carrying amount of the related long-lived asset and depreciated over the asset’s remaining useful life. The following table presents the activity for the asset retirement obligations for the years ended January 2, 2021 and December 28, 2019: 2020 2019 Beginning balance $ 36,676 $ 30,999 Acquired obligations 861 805 Change in cost estimate 6,523 4,468 Settlement of reclamation obligations (3,095) (1,812) Accretion expense 2,638 2,216 Ending balance $ 43,603 $ 36,676
Summit Materials, LLC
Asset Retirement Obligations [Line Items]
Accrued Mining and Landfill Reclamation	Accrued Mining and Landfill Reclamation The Company has asset retirement obligations arising from regulatory or contractual requirements to perform certain reclamation activities at the time that certain quarries and landfills are closed, which are primarily included in other noncurrent liabilities on the consolidated balance sheets. The current portion of the liabilities, $10.0 million and $7.9 million as of January 2, 2021 and December 28, 2019, respectively, is included in accrued expenses on the consolidated balance sheets. The total undiscounted anticipated costs for site reclamation as of January 2, 2021 and December 28, 2019 were $112.8 million and $97.4 million, respectively. The liabilities were initially measured at fair value and are subsequently adjusted for accretion expense, payments and changes in the amount or timing of the estimated cash flows. The corresponding asset retirement costs are capitalized as part of the carrying amount of the related long-lived asset and depreciated over the asset’s remaining useful life. The following table presents the activity for the asset retirement obligations for the years ended January 2, 2021 and December 28, 2019: 2020 2019 Beginning balance $ 36,676 $ 30,999 Acquired obligations 861 805 Change in cost estimate 6,523 4,468 Settlement of reclamation obligations (3,095) (1,812) Accretion expense 2,638 2,216 Ending balance $ 43,603 $ 36,676

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Jan. 02, 2021
Loss Contingencies [Line Items]
Commitments and Contingencies	Commitments and Contingencies The Company is party to certain legal actions arising from the ordinary course of business activities. Accruals are recorded when the outcome is probable and can be reasonably estimated. While the ultimate results of claims and litigation cannot be predicted with certainty, management expects that the ultimate resolution of all current pending or threatened claims and litigation will not have a material effect on the Company’s consolidated financial position, results of operations or liquidity. The Company records legal fees as incurred. In March 2018, we were notified of an investigation by the Canadian Competition Bureau (the “CCB”) into pricing practices by certain asphalt paving contractors in British Columbia, including Winvan Paving, Ltd. (“Winvan”). We believe the investigation is focused on time periods prior to our April 2017 acquisition of Winvan and we are cooperating with the CCB. Although we currently do not believe this matter will have a material adverse effect on our business, financial condition or results of operations, we are not able to predict the ultimate outcome or cost of the investigation at this time. Environmental Remediation and Site Restoration— The Company’s operations are subject to and affected by federal, state, provincial and local laws and regulations relating to the environment, health and safety and other regulatory matters. These operations require environmental operating permits, which are subject to modification, renewal and revocation. The Company regularly monitors and reviews its operations, procedures and policies for compliance with these laws and regulations. Despite these compliance efforts, risk of environmental liability is inherent in the operation of the Company’s business, as it is with other companies engaged in similar businesses and there can be no assurance that environmental liabilities or noncompliance will not have a material adverse effect on the Company’s consolidated financial condition, results of operations or liquidity. Other— The Company is obligated under various firm purchase commitments for certain raw materials and services that are in the ordinary course of business. Management does not expect any significant changes in the market value of these goods and services during the commitment period that would have a material adverse effect on the financial condition, results of operations and cash flows of the Company. The terms of the purchase commitments generally approximate one year.
Summit Materials, LLC
Loss Contingencies [Line Items]
Commitments and Contingencies	Commitments and Contingencies The Company is party to certain legal actions arising from the ordinary course of business activities. Accruals are recorded when the outcome is probable and can be reasonably estimated. While the ultimate results of claims and litigation cannot be predicted with certainty, management expects that the ultimate resolution of all current pending or threatened claims and litigation will not have a material effect on the Company’s consolidated financial position, results of operations or liquidity. The Company records legal fees as incurred. In March 2018, we were notified of an investigation by the Canadian Competition Bureau (the “CCB”) into pricing practices by certain asphalt paving contractors in British Columbia, including Winvan Paving, Ltd. (“Winvan”). We believe the investigation is focused on time periods prior to our April 2017 acquisition of Winvan and we are cooperating with the CCB. Although we currently do not believe this matter will have a material adverse effect on our business, financial condition or results of operations, we are not able to predict the ultimate outcome or cost of the investigation at this time. Environmental Remediation and Site Restoration— The Company’s operations are subject to and affected by federal, state, provincial and local laws and regulations relating to the environment, health and safety and other regulatory matters. These operations require environmental operating permits, which are subject to modification, renewal and revocation. The Company regularly monitors and reviews its operations, procedures and policies for compliance with these laws and regulations. Despite these compliance efforts, risk of environmental liability is inherent in the operation of the Company’s business, as it is with other companies engaged in similar businesses and there can be no assurance that environmental liabilities or noncompliance will not have a material adverse effect on the Company’s consolidated financial condition, results of operations or liquidity.

Leases

Leases	12 Months Ended
	Jan. 02, 2021
Lessee, Lease, Description [Line Items]
Leases	Leases We lease construction and office equipment, distribution facilities and office space. Leases with an initial term of 12 months or less, including month to month leases, are not recorded on the balance sheet. Lease expense for short-term leases is recognized on a straight line basis over the lease term. For lease agreements entered into or reassessed after the adoption of Topic 842, we combine lease and nonlease components. While we also own mineral leases for mining operations, those leases are outside the scope of Topic 842. Assets acquired under finance leases are included in property, plant and equipment. Many of our leases include options to purchase the leased equipment. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328 The Company has lease agreements associated with quarry facilities under which royalty payments are made. The payments are generally based on tons sold in a particular period; however, certain agreements have minimum annual payments. Royalty expense recorded in cost of revenue during the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was $29.2 million, $24.3 million and $20.1 million, respectively. Minimum contractual commitments for the subsequent five years under royalty agreements are as follows: Royalty Agreements 2021 $ 9,916 2022 9,880 2023 9,594 2024 9,295 2025 9,052
Leases	Leases We lease construction and office equipment, distribution facilities and office space. Leases with an initial term of 12 months or less, including month to month leases, are not recorded on the balance sheet. Lease expense for short-term leases is recognized on a straight line basis over the lease term. For lease agreements entered into or reassessed after the adoption of Topic 842, we combine lease and nonlease components. While we also own mineral leases for mining operations, those leases are outside the scope of Topic 842. Assets acquired under finance leases are included in property, plant and equipment. Many of our leases include options to purchase the leased equipment. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328 The Company has lease agreements associated with quarry facilities under which royalty payments are made. The payments are generally based on tons sold in a particular period; however, certain agreements have minimum annual payments. Royalty expense recorded in cost of revenue during the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was $29.2 million, $24.3 million and $20.1 million, respectively. Minimum contractual commitments for the subsequent five years under royalty agreements are as follows: Royalty Agreements 2021 $ 9,916 2022 9,880 2023 9,594 2024 9,295 2025 9,052
Summit Materials, LLC
Lessee, Lease, Description [Line Items]
Leases	Leases We lease construction and office equipment, distribution facilities and office space. Leases with an initial term of 12 months or less, including month to month leases, are not recorded on the balance sheet. Lease expense for short-term leases is recognized on a straight line basis over the lease term. For lease agreements entered into or reassessed after the adoption of Topic 842, we combine lease and nonlease components. While we also own mineral leases for mining operations, those leases are outside the scope of Topic 842. Assets acquired under finance leases are included in property, plant and equipment. Many of our leases include options to purchase the leased equipment. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328 The Company has lease agreements associated with quarry facilities under which royalty payments are made. The payments are generally based on tons sold in a particular period; however, certain agreements have minimum annual payments. Royalty expense recorded in cost of revenue during the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was $29.2 million, $24.3 million and $20.1 million, respectively. Minimum contractual commitments for the subsequent five years under royalty agreements are as follows: Royalty Agreements 2021 $ 9,916 2022 9,880 2023 9,594 2024 9,295 2025 9,052
Leases	Leases We lease construction and office equipment, distribution facilities and office space. Leases with an initial term of 12 months or less, including month to month leases, are not recorded on the balance sheet. Lease expense for short-term leases is recognized on a straight line basis over the lease term. For lease agreements entered into or reassessed after the adoption of Topic 842, we combine lease and nonlease components. While we also own mineral leases for mining operations, those leases are outside the scope of Topic 842. Assets acquired under finance leases are included in property, plant and equipment. Many of our leases include options to purchase the leased equipment. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328 The Company has lease agreements associated with quarry facilities under which royalty payments are made. The payments are generally based on tons sold in a particular period; however, certain agreements have minimum annual payments. Royalty expense recorded in cost of revenue during the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was $29.2 million, $24.3 million and $20.1 million, respectively. Minimum contractual commitments for the subsequent five years under royalty agreements are as follows: Royalty Agreements 2021 $ 9,916 2022 9,880 2023 9,594 2024 9,295 2025 9,052

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Jan. 02, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair Value Measurements— Certain acquisitions made by the Company require the payment of contingent amounts of purchase consideration. These payments are contingent on specified operating results being achieved in periods subsequent to the acquisition and will only be made if earn-out thresholds are achieved. Contingent consideration obligations are measured at fair value each reporting period. Any adjustments to fair value are recognized in earnings in the period identified. The fair value of contingent consideration as of January 2, 2021 and December 28, 2019 was: 2020 2019 Current portion of acquisition-related liabilities and Accrued expenses: Contingent consideration $ 654 $ 1,967 Acquisition-related liabilities and Other noncurrent liabilities: Contingent consideration $ 1,209 $ 1,302 The fair value accounting guidance establishes the following fair value hierarchy that prioritizes the inputs used to measure fair value: Level 1 — Quoted prices in active markets for identical assets and liabilities. Level 2 — Observable inputs, other than quoted prices, for similar assets or liabilities in active markets. Level 3 — Unobservable inputs, which includes the use of valuation models. Financial Instruments —The Company’s financial instruments include debt and certain acquisition-related liabilities (deferred consideration and noncompete obligations). The carrying value and fair value of these financial instruments as of January 2, 2021 and December 28, 2019 were: January 2, 2021 December 28, 2019 Fair Value Carrying Value Fair Value Carrying Value Level 1 Long-term debt(1) $ 1,971,087 $ 1,915,425 $ 1,918,720 $ 1,872,273 Level 3 Current portion of deferred consideration and noncompete obligations(2) 9,611 9,611 30,733 30,733 Long term portion of deferred consideration and noncompete obligations(3) 11,037 11,037 18,499 18,499 _____________________ (1) $6.4 million and $7.9 million were included in current portion of debt as of January 2, 2021 and December 28, 2019, respectively. (2) Included in current portion of acquisition-related liabilities on the consolidated balance sheets. (3) Included in acquisition-related liabilities on the consolidated balance sheets. Level 1 fair values are used to value investments in publicly-traded entities and assumed obligations for publicly-traded long-term debt. Level 2 fair values are typically used to value acquired receivables, inventories, machinery and equipment, land, buildings, deferred income tax assets and liabilities, liabilities for asset retirement obligations, environmental remediation and compliance obligations. Additionally, Level 2 fair values are typically used to value assumed contracts at other-than-market rates. Level 3 fair values are used to value acquired mineral reserves and leased mineral interests and other identifiable intangible assets. The fair values of mineral reserves and leased mineral interests are determined using an excess earnings approach, which requires management to estimate future cash flows. The estimate of future cash flows is based on available historical information and forecasts determined by management, but is inherently uncertain. Key assumptions in estimating future cash flows include sales price, volumes and expected profit margins, net of capital requirements. The present value of the projected net cash flows represents the fair value assigned to mineral reserves and mineral interests. The discount rate is a significant assumption used in the valuation model and is based on the required rate of return that a hypothetical market participant would assume if purchasing the acquired business. The Level 3 fair values of contingent consideration were based on projected probability-weighted cash payments and a 9.5% discount rate, which reflects a market discount rate. Changes in fair value may occur as a result of a change in actual or projected cash payments, the probability weightings applied by the Company to projected payments or a change in the discount rate. Significant increases or decreases in any of these inputs in isolation could result in a lower, or higher, fair value measurement. There were no material adjustments to the fair value of contingent consideration in 2020 or 2019. The fair values of the deferred consideration and noncompete obligations were determined based on the cash payment terms in the purchase agreements and a discount rate reflecting the Company’s credit risk. The discount rate used is generally consistent with that used when the obligations were initially recorded. Securities with a maturity of three months or less are considered cash equivalents and the fair value of these assets approximates their carrying value.
Summit Materials, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair Value Measurements— Certain acquisitions made by the Company require the payment of contingent amounts of purchase consideration. These payments are contingent on specified operating results being achieved in periods subsequent to the acquisition and will only be made if earn-out thresholds are achieved. Contingent consideration obligations are measured at fair value each reporting period. Any adjustments to fair value are recognized in earnings in the period identified. The fair value of contingent consideration as of January 2, 2021 and December 28, 2019 was: 2020 2019 Current portion of acquisition-related liabilities and Accrued expenses: Contingent consideration $ 654 $ 1,967 Acquisition-related liabilities and Other noncurrent liabilities: Contingent consideration $ 1,209 $ 1,302 The fair value accounting guidance establishes the following fair value hierarchy that prioritizes the inputs used to measure fair value: Level 1 — Quoted prices in active markets for identical assets and liabilities. Level 2 — Observable inputs, other than quoted prices, for similar assets or liabilities in active markets. Level 3 — Unobservable inputs, which includes the use of valuation models. Financial Instruments —The Company’s financial instruments include debt and certain acquisition-related liabilities (deferred consideration and noncompete obligations). The carrying value and fair value of these financial instruments as of January 2, 2021 and December 28, 2019 were: January 2, 2021 December 28, 2019 Fair Value Carrying Value Fair Value Carrying Value Level 1 Long-term debt(1) $ 1,971,087 $ 1,915,425 $ 1,918,720 $ 1,872,273 Level 3 Current portion of deferred consideration and noncompete obligations(2) 7,173 7,173 28,233 28,233 Long term portion of deferred consideration and noncompete obligations(3) 11,037 11,037 16,364 16,364 ______________________ (1) $6.4 million and $7.9 million were included in current portion of debt as of January 2, 2021 and December 28, 2019, respectively. (2) Included in current portion of acquisition-related liabilities on the consolidated balance sheets. (3) Included in acquisition-related liabilities on the consolidated balance sheets. Level 1 fair values are used to value investments in publicly-traded entities and assumed obligations for publicly-traded long-term debt. Level 2 fair values are typically used to value acquired receivables, inventories, machinery and equipment, land, buildings, deferred income tax assets and liabilities, liabilities for asset retirement obligations, environmental remediation and compliance obligations. Additionally, Level 2 fair values are typically used to value assumed contracts at other-than-market rates. Level 3 fair values are used to value acquired mineral reserves and leased mineral interests and other identifiable intangible assets. The fair values of mineral reserves and leased mineral interests are determined using an excess earnings approach, which requires management to estimate future cash flows. The estimate of future cash flows is based on available historical information and forecasts determined by management, but is inherently uncertain. Key assumptions in estimating future cash flows include sales price, volumes and expected profit margins, net of capital requirements. The present value of the projected net cash flows represents the fair value assigned to mineral reserves and mineral interests. The discount rate is a significant assumption used in the valuation model and is based on the required rate of return that a hypothetical market participant would assume if purchasing the acquired business. The Level 3 fair values of contingent consideration were based on projected probability-weighted cash payments and a 9.5% discount rate, which reflects a market discount rate. Changes in fair value may occur as a result of a change in actual or projected cash payments, the probability weightings applied by the Company to projected payments or a change in the discount rate. Significant increases or decreases in any of these inputs in isolation could result in a lower, or higher, fair value measurement. There were no material adjustments to the fair value of contingent consideration in 2020 or 2019. The fair values of the deferred consideration and noncompete obligations were determined based on the cash payment terms in the purchase agreements and a discount rate reflecting the Company’s credit risk. The discount rate used is generally consistent with that used when the obligations were initially recorded. Securities with a maturity of three months or less are considered cash equivalents and the fair value of these assets approximates their carrying value.

Segment Information

Segment Information	12 Months Ended
	Jan. 02, 2021
Segment Reporting Information [Line Items]
Segment Information	Segment Information The Company has three operating segments: West; East; and Cement, which are its reporting segments. These segments are consistent with the Company’s management reporting structure. The operating results of each segment are regularly reviewed and evaluated by the Chief Executive Officer, the Company’s Chief Operating Decision Maker (“CODM”). The CODM primarily evaluates the performance of its segments and allocates resources to them based on a segment profit metric that we call Adjusted EBITDA, which is computed as earnings from continuing operations before interest, taxes, depreciation, depletion, amortization, accretion, share-based compensation, and transaction costs, as well as various other non-recurring, non-cash amounts. The West and East segments have several acquired subsidiaries that are engaged in various activities including quarry mining, aggregate production and contracting. The Cement segment is engaged in the production of Portland cement. Assets employed by each segment include assets directly identified with those operations. Corporate assets consist primarily of cash, property, plant and equipment for corporate operations and other assets not directly identifiable with a reportable business segment. The accounting policies applicable to each segment are consistent with those used in the consolidated financial statements. The following tables display selected financial data for the Company’s reportable business segments as of and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Revenue*: West $ 1,262,196 $ 1,122,338 $ 1,117,066 East 799,633 809,098 703,147 Cement 270,622 290,704 280,789 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ * Intercompany sales are immaterial and the presentation above only reflects sales to external customers. 2020 2019 2018 Income from operations before taxes $ 129,055 $ 78,224 $ 96,077 Interest expense 103,595 116,509 116,548 Depreciation, depletion and amortization 218,682 214,886 203,305 Accretion 2,638 2,216 1,605 Loss on debt financings 4,064 14,565 149 Tax receivable agreement (benefit) expense (7,559) 16,237 (22,684) Gain on sale of business — — (12,108) Transaction costs 2,747 2,222 4,238 Non-cash compensation 28,857 20,403 25,378 Other 2,957 (3,800) (6,247) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 Total Adjusted EBITDA by Segment: West $ 271,052 $ 204,964 $ 188,999 East 162,275 187,625 138,032 Cement 92,956 103,438 111,394 Corporate and other (41,247) (34,565) (32,164) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 2020 2019 2018 Purchases of property, plant and equipment West $ 67,500 $ 71,397 $ 120,657 East 92,528 77,894 64,384 Cement 15,071 25,691 28,036 Total reportable segments 175,099 174,982 213,077 Corporate and other 2,150 2,513 7,608 Total purchases of property, plant and equipment $ 177,249 $ 177,495 $ 220,685 2020 2019 2018 Depreciation, depletion, amortization and accretion: West $ 93,866 $ 93,256 $ 91,794 East 86,205 81,403 75,433 Cement 37,267 38,447 35,061 Total reportable segments 217,338 213,106 202,288 Corporate and other 3,982 3,996 2,622 Total depreciation, depletion, amortization and accretion $ 221,320 $ 217,102 $ 204,910 2020 2019 2018 Total assets: West $ 1,503,382 $ 1,379,684 $ 1,370,501 East 1,303,742 1,288,835 1,253,640 Cement 850,835 868,528 877,586 Total reportable segments 3,657,959 3,537,047 3,501,727 Corporate and other 650,052 530,509 355,914 Total $ 4,308,011 $ 4,067,556 $ 3,857,641
Summit Materials, LLC
Segment Reporting Information [Line Items]
Segment Information	Segment Information The Company has three operating segments: West; East; and Cement, which are its reporting segments. These segments are consistent with the Company’s management reporting structure. The operating results of each segment are regularly reviewed and evaluated by the Chief Executive Officer, the Company’s Chief Operating Decision Maker (“CODM”). The CODM primarily evaluates the performance of its segments and allocates resources to them based on a segment profit metric that we call Adjusted EBITDA, which is computed as earnings from continuing operations before interest, taxes, depreciation, depletion, amortization, accretion, share-based compensation, and transaction costs, as well as various other non-recurring, non-cash amounts. The West and East segments have several acquired subsidiaries that are engaged in various activities including quarry mining, aggregate production and contracting. The Cement segment is engaged in the production of Portland cement. Assets employed by each segment include assets directly identified with those operations. Corporate assets consist primarily of cash, property, plant and equipment for corporate operations and other assets not directly identifiable with a reportable business segment. The accounting policies applicable to each segment are consistent with those used in the consolidated financial statements. The following tables display selected financial data for the Company’s reportable business segments as of and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Revenue*: West $ 1,262,196 $ 1,122,338 $ 1,117,066 East 799,633 809,098 703,147 Cement 270,622 290,704 280,789 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ * Intercompany sales are immaterial and the presentation above only reflects sales to external customers. 2020 2019 2018 Income from operations before taxes $ 121,800 $ 94,982 $ 74,110 Interest expense 103,291 115,988 115,831 Depreciation, depletion and amortization 218,682 214,886 203,305 Accretion 2,638 2,216 1,605 Loss on debt financings 4,064 14,565 149 Gain on sale of business — — (12,108) Transaction costs 2,747 2,222 4,238 Non-cash compensation 28,857 20,403 25,378 Other 2,957 (3,800) (6,247) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 Total Adjusted EBITDA by Segment: West $ 271,052 $ 204,964 $ 188,999 East 162,275 187,625 138,032 Cement 92,956 103,438 111,394 Corporate and other (41,247) (34,565) (32,164) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 2020 2019 2018 Purchases of property, plant and equipment West $ 67,500 $ 71,397 $ 120,657 East 92,528 77,894 64,384 Cement 15,071 25,691 28,036 Total reportable segments 175,099 174,982 213,077 Corporate and other 2,150 2,513 7,608 Total purchases of property, plant and equipment $ 177,249 $ 177,495 $ 220,685 2020 2019 2018 Depreciation, depletion, amortization and accretion: West $ 93,866 $ 93,256 $ 91,794 East 86,205 81,403 75,433 Cement 37,267 38,447 35,061 Total reportable segments 217,338 213,106 202,288 Corporate and other 3,982 3,996 2,622 Total depreciation, depletion, amortization and accretion $ 221,320 $ 217,102 $ 204,910 2020 2019 2018 Total assets: West $ 1,503,382 $ 1,379,684 $ 1,370,501 East 1,303,742 1,288,835 1,253,640 Cement 850,835 868,528 877,586 Total reportable segments 3,657,959 3,537,047 3,501,727 Corporate and other 419,175 319,176 131,517 Total $ 4,077,134 $ 3,856,223 $ 3,633,244

Senior Notes' Guarantor and Non

Senior Notes' Guarantor and Non-Guarantor Financial Information	12 Months Ended
	Jan. 02, 2021
Summit Materials, LLC
Condensed Financial Statements, Captions [Line Items]
Senior Notes' Guarantor and Non-Guarantor Financial Information	Senior Notes’ Guarantor and Non-Guarantor Financial Information Summit LLC’s domestic wholly-owned subsidiary companies other than Finance Corp. are named as guarantors (collectively, the “Guarantors”) of the Senior Notes. Certain other partially-owned subsidiaries and a non-U.S. entity do not guarantee the Senior Notes (collectively, the “Non-Guarantors”). The Guarantors provide a joint and several, full and unconditional guarantee of the Senior Notes. There are no significant restrictions on Summit LLC’s ability to obtain funds from any of the Guarantor Subsidiaries in the form of dividends or loans. Additionally, there are no significant restrictions on a Guarantor Subsidiary’s ability to obtain funds from Summit LLC or its direct or indirect subsidiaries. The following condensed consolidating balance sheets, statements of operations and cash flows are provided for the Issuers, the Wholly-owned Guarantors and the Non-Guarantors. Earnings from subsidiaries are included in other income in the condensed consolidated statements of operations below. The financial information may not necessarily be indicative of the financial position, results of operations or cash flows had the guarantor or non-guarantor subsidiaries operated as independent entities. Condensed Consolidating Balance Sheets January 2, 2021 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Assets Current assets: Cash and cash equivalents $ 401,074 $ 10,287 $ 10,461 $ (3,641) $ 418,181 Accounts receivable, net 4 230,199 24,384 109 254,696 Intercompany receivables 404,459 1,303,293 — (1,707,752) — Cost and estimated earnings in excess of billings — 7,504 1,162 — 8,666 Inventories — 193,417 6,891 — 200,308 Other current assets 2,840 6,797 1,791 — 11,428 Total current assets 808,377 1,751,497 44,689 (1,711,284) 893,279 Property, plant and equipment, net 9,410 1,746,045 94,714 — 1,850,169 Goodwill — 1,142,083 60,208 — 1,202,291 Intangible assets, net — 47,852 — — 47,852 Operating lease right-of-use assets 2,615 21,880 4,048 — 28,543 Other assets 4,022,729 207,699 493 (4,175,921) 55,000 Total assets $ 4,843,131 $ 4,917,056 $ 204,152 $ (5,887,205) $ 4,077,134 Liabilities and Member’s Interest Current liabilities: Current portion of debt $ 6,354 $ — $ — $ — $ 6,354 Current portion of acquisition-related liabilities — 7,827 — — 7,827 Accounts payable 3,889 108,805 8,619 109 121,422 Accrued expenses 54,108 106,320 4,014 (3,641) 160,801 Current operating lease liabilities 913 6,114 1,161 — 8,188 Intercompany payables 1,215,043 485,401 7,308 (1,707,752) — Billings in excess of costs and estimated earnings — 15,508 991 — 16,499 Total current liabilities 1,280,307 729,975 22,093 (1,711,284) 321,091 Long-term debt 1,892,347 — — — 1,892,347 Acquisition-related liabilities — 12,246 — — 12,246 Noncurrent operating lease liabilities 2,567 16,062 2,871 — 21,500 Other noncurrent liabilities 5,142 208,540 117,921 (164,421) 167,182 Total liabilities 3,180,363 966,823 142,885 (1,875,705) 2,414,366 Total member's interest 1,662,768 3,950,233 61,267 (4,011,500) 1,662,768 Total liabilities and member’s interest $ 4,843,131 $ 4,917,056 $ 204,152 $ (5,887,205) $ 4,077,134 Condensed Consolidating Balance Sheets December 28, 2019 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Assets Current assets: Cash and cash equivalents $ 302,474 $ 5,488 $ 9,834 $ (6,477) $ 311,319 Accounts receivable, net — 234,053 19,236 (33) 253,256 Intercompany receivables 443,323 942,385 — (1,385,708) — Cost and estimated earnings in excess of billings — 12,291 797 — 13,088 Inventories — 199,794 4,993 — 204,787 Other current assets 1,763 10,308 1,760 — 13,831 Total current assets 747,560 1,404,319 36,620 (1,392,218) 796,281 Property, plant and equipment, net 11,602 1,674,443 61,404 — 1,747,449 Goodwill — 1,142,063 58,636 — 1,200,699 Intangible assets, net — 23,498 — — 23,498 Operating lease right-of-use assets 3,316 24,551 4,910 — 32,777 Other assets 3,596,161 168,314 734 (3,709,690) 55,519 Total assets $ 4,358,639 $ 4,437,188 $ 162,304 $ (5,101,908) $ 3,856,223 Liabilities and Member’s Interest Current liabilities: Current portion of debt $ 7,942 $ — $ — $ — $ 7,942 Current portion of acquisition-related liabilities — 30,200 — — 30,200 Accounts payable 4,588 103,812 8,603 (33) 116,970 Accrued expenses 51,043 72,970 2,701 (6,477) 120,237 Current operating lease liabilities 764 6,571 1,092 — 8,427 Intercompany payables 922,356 447,827 15,525 (1,385,708) — Billings in excess of costs and estimated earnings — 12,183 1,681 — 13,864 Total current liabilities 986,693 673,563 29,602 (1,392,218) 297,640 Long-term debt 1,851,057 — — — 1,851,057 Acquisition-related liabilities — 17,666 — — 17,666 Noncurrent operating lease liabilities 3,480 18,047 3,854 — 25,381 Other noncurrent liabilities 4,259 203,919 80,169 (137,018) 151,329 Total liabilities 2,845,489 913,195 113,625 (1,529,236) 2,343,073 Total member's interest 1,513,150 3,523,993 48,679 (3,572,672) 1,513,150 Total liabilities and member’s interest $ 4,358,639 $ 4,437,188 $ 162,304 $ (5,101,908) $ 3,856,223 Condensed Consolidating Statements of Operations and Comprehensive Income Year Ended January 2, 2021 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Revenue $ — $ 2,259,865 $ 89,752 $ (17,166) $ 2,332,451 Cost of revenue (excluding items shown separately below) — 1,542,586 58,576 (17,166) 1,583,996 General and administrative expenses 72,504 217,897 11,561 — 301,962 Depreciation, depletion, amortization and accretion 3,983 210,038 7,299 — 221,320 Operating (loss) income (76,487) 289,344 12,316 — 225,173 Other (income) loss, net (328,914) (2,473) (198) 331,667 82 Interest expense (income) 130,176 (31,402) 4,517 — 103,291 Income from operation before taxes 122,251 323,219 7,997 (331,667) 121,800 Income tax expense (benefit) 1,514 (4,737) 4,286 — 1,063 Net income attributable to Summit LLC $ 120,737 $ 327,956 $ 3,711 $ (331,667) $ 120,737 Comprehensive income (loss) attributable to member of Summit Materials, LLC $ 123,125 $ 330,185 $ (906) $ (329,279) $ 123,125 Condensed Consolidating Statements of Operations and Comprehensive Income Year ended December 28, 2019 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Revenue $ — $ 2,139,457 $ 94,879 $ (12,196) $ 2,222,140 Cost of revenue (excluding items shown separately below) — 1,473,124 65,404 (12,196) 1,526,332 General and administrative expenses 58,099 195,683 11,366 — 265,148 Depreciation, depletion, amortization and accretion 3,997 207,277 5,828 — 217,102 Operating (loss) income (62,096) 263,373 12,281 — 213,558 Other (income) loss, net (279,517) (8,767) (790) 291,662 2,588 Interest expense (income) 127,734 (16,561) 4,815 — 115,988 Income from operation before taxes 89,687 288,701 8,256 (291,662) 94,982 Income tax expense 1,090 3,377 1,918 — 6,385 Net income attributable to Summit LLC $ 88,597 $ 285,324 $ 6,338 $ (291,662) $ 88,597 Comprehensive income attributable to member of Summit Materials, LLC $ 91,242 $ 287,395 $ 1,622 $ (289,017) $ 91,242 Condensed Consolidating Statements of Operations and Comprehensive Income Year ended December 29, 2018 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Revenue $ — $ 2,018,428 $ 88,658 $ (6,084) $ 2,101,002 Cost of revenue (excluding items shown separately below) — 1,416,222 65,641 (6,084) 1,475,779 General and administrative expenses 62,376 184,917 10,554 — 257,847 Depreciation, depletion, amortization and accretion 2,622 197,406 4,882 — 204,910 Operating (loss) income (64,998) 219,883 7,581 — 162,466 Other (income) loss, net (249,204) (14,643) 823 247,657 (15,367) Interest expense 118,857 (7,818) 4,792 — 115,831 Gain on sale of business — (12,108) — — (12,108) Income from continuing operations before taxes 65,349 254,452 1,966 (247,657) 74,110 Income tax (benefit) expense 1,512 8,226 535 — 10,273 Net income attributable to member of Summit Materials, LLC $ 63,837 $ 246,226 $ 1,431 $ (247,657) $ 63,837 Comprehensive income attributable to member of Summit Materials, LLC $ 57,356 $ 243,359 $ 10,779 $ (254,138) $ 57,356 Condensed Consolidating Statements of Cash Flows For the year ended January 2, 2021 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Net cash (used in) provided by operating activities $ (135,895) $ 502,595 $ 42,169 $ — $ 408,869 Cash flow from investing activities: Acquisitions, net of cash acquired — (92,085) (31,392) — (123,477) Purchase of property, plant and equipment (2,150) (173,228) (1,871) — (177,249) Proceeds from the sale of property, plant, and equipment — 13,935 83 — 14,018 Other — 1,121 — — 1,121 Net cash used for investing activities (2,150) (250,257) (33,180) — (285,587) Cash flow from financing activities: Proceeds from investment by member (91,142) 87,925 4,260 — 1,043 Net proceeds from debt issuance 700,000 — — — 700,000 Loans received from and payments made on loans from other Summit Companies 298,656 (288,711) (12,781) 2,836 — Payments on long-term debt (657,942) (15,911) (192) — (674,045) Payments on acquisition-related liabilities — (30,757) — — (30,757) Debt issuance costs (9,605) — — — (9,605) Distributions from partnership (2,500) — — — (2,500) Other (822) (85) — — (907) Net cash provided by (used in) financing activities 236,645 (247,539) (8,713) 2,836 (16,771) Impact of cash on foreign currency — — 351 — 351 Net increase in cash 98,600 4,799 627 2,836 106,862 Cash — Beginning of period 302,474 5,488 9,834 (6,477) 311,319 Cash — End of period $ 401,074 $ 10,287 $ 10,461 $ (3,641) $ 418,181 Condensed Consolidating Statements of Cash Flows For the year ended December 28, 2019 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Net cash (used in) provided by operating activities $ (112,019) $ 431,323 $ 17,880 $ — $ 337,184 Cash flow from investing activities: Acquisitions, net of cash acquired — (5,392) — — (5,392) Purchase of property, plant and equipment (2,513) (163,652) (11,330) — (177,495) Proceeds from the sale of property, plant, and equipment — 21,083 90 — 21,173 Proceeds from the sale of a business — 21,564 — — 21,564 Other — (1,095) — — (1,095) Net cash used for investing activities (2,513) (149,056) (11,240) — (162,809) Cash flow from financing activities: Proceeds from investment by member (21,614) 40,690 — — 19,076 Net proceeds from debt issuance 300,000 — — — 300,000 Loans received from and payments made on loans from other Summit Companies 287,029 (280,836) (4,586) (1,607) — Payments on long-term debt (256,354) (13,650) (225) — (270,229) Payments on acquisition-related liabilities — (31,383) — — (31,383) Financing costs (6,312) — — — (6,312) Distributions from partnership (2,500) — — — (2,500) Other (462) (40) — — (502) Net cash provided by (used in) financing activities 299,787 (285,219) (4,811) (1,607) 8,150 Impact of cash on foreign currency — — 286 — 286 Net increase (decrease) in cash 185,255 (2,952) 2,115 (1,607) 182,811 Cash — Beginning of period 117,219 8,440 7,719 (4,870) 128,508 Cash — End of period $ 302,474 $ 5,488 $ 9,834 $ (6,477) $ 311,319 Condensed Consolidating Statements of Cash Flows For the year ended December 29, 2018 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Net cash (used in) provided by operating activities $ (142,315) $ 340,401 $ 11,282 $ — $ 209,368 Cash flow from investing activities: Acquisitions, net of cash acquired — (246,017) — — (246,017) Purchase of property, plant and equipment (7,607) (188,435) (24,643) — (220,685) Proceeds from the sale of property, plant, and equipment — 21,263 372 — 21,635 Proceeds from the sale of a business — 21,564 — — 21,564 Other — 3,804 — — 3,804 Net cash used for investing activities (7,607) (387,821) (24,271) — (419,699) Cash flow from financing activities: Proceeds from investment by member (146,533) 162,148 — — 15,615 Net proceeds from debt issuance 64,500 — — — 64,500 Loans received from and payments made on loans from other Summit Companies 51,696 (65,845) 6,647 7,502 — Payments on long-term debt (69,265) (15,662) (115) — (85,042) Payments on acquisition-related liabilities — (34,004) — — (34,004) Financing costs (550) — — — (550) Distributions from partnership (2,569) — — — (2,569) Other (879) (1,031) (33) — (1,943) Net cash provided by financing activities (103,600) 45,606 6,499 7,502 (43,993) Impact of cash on foreign currency — — (724) — (724) Net (decrease) increase in cash (253,522) (1,814) (7,214) 7,502 (255,048) Cash — Beginning of period 370,741 10,254 14,933 (12,372) 383,556 Cash — End of period $ 117,219 $ 8,440 $ 7,719 $ (4,870) $ 128,508

Summary of Organization and S_2

Summary of Organization and Significant Accounting Policies (Policies)	12 Months Ended
	Jan. 02, 2021
Company Information
Principles of Consolidation	Principles of Consolidation —The consolidated financial statements include the accounts of Summit Inc. and its majority owned subsidiaries. All intercompany balances and transactions have been eliminated. As a result of the Reorganization, Summit Holdings became a variable interest entity over which Summit Inc. has 100% voting power and control and for which Summit Inc. has the obligation to absorb losses and the right to receive benefits. The Company’s fiscal year is based on a 52-53 week year with each quarter composed of 13 weeks ending on a Saturday. The year ended January 2, 2021 was a 53-week year. For a summary of the changes in Summit Inc.’s ownership of Summit Holdings, see Note 11, Stockholders’ Equity.
Use of Estimates	Use of Estimates—Preparation of these consolidated financial statements in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) requires management to make estimates and assumptions. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities and reported amounts of revenue and expenses. Such estimates include the valuation of accounts receivable, inventories, valuation of deferred tax assets, goodwill, intangibles and other long-lived assets, the tax receivable agreement (“TRA”) liability, pension and other postretirement obligations, and asset retirement obligations. Estimates also include revenue earned on contracts and costs to complete contracts. Most of the Company’s paving and related services are performed under fixed unit-price contracts with state and local governmental entities. Management regularly evaluates its estimates and assumptions based on historical experience and other factors, including the current economic environment. As future events and their effects cannot be determined with precision, actual results can differ significantly from estimates made. Changes in estimates, including those resulting from continuing changes in the economic environment, are reflected in the Company’s consolidated financial statements when the change in estimate occurs.
Business and Credit Concentrations	Business and Credit Concentrations—The Company’s operations are conducted primarily across 23 U.S. states and in British Columbia, Canada, with the most significant revenue generated in Texas, Utah, Kansas and Missouri. The Company’s accounts receivable consist primarily of amounts due from customers within these areas. Therefore, collection of these accounts is dependent on the economic conditions in the aforementioned states, as well as specific situations affecting individual customers. Credit granted within the Company’s trade areas has been granted to many customers and management does not believe that a significant concentration of credit exists with respect to any individual customer or group of customers.
Accounts Receivable	Accounts Receivable —Accounts receivable are stated at the amount management expects to collect from outstanding balances. Management provides for probable uncollectible amounts through a charge to earnings and a credit to a valuation allowance based on its assessment of the collectability of individual accounts. In establishing the allowance, management considers historical losses adjusted to take into account current market conditions and its customers’ financial condition, the amount of receivables in dispute, the current receivables aging and current payment terms. Balances that remain outstanding after reasonable collection efforts are exercised are written off through a charge to the valuation allowance. The balances billed but not paid by customers, pursuant to retainage provisions included in contracts, are generally due upon completion of the contracts.
Revenue Recognition	Revenue Recognition —We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products and plastics components, and from the provision of services, which are primarily paving and related services, but also include landfill operations, the receipt and disposal of waste that is converted to fuel for use in our cement plants. Products We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products, net of discounts or allowances, if any, and freight and delivery charges billed to customers. Revenue for product sales is recognized when evidence of an arrangement exists and when control passes, which generally is when the product is shipped. Aggregates and cement products are sold point-of-sale through purchase orders. When the product is sold on account, collectability typically occurs 30 to 60 days after the sale. Revenue is recognized when cash is received from the customer at the point of sale or when the products are delivered or collected on site. There are no other timing implications that will create a contract asset or liability, and contract modifications are unlikely given the timing and nature of the transaction. Material sales are likely to have multiple performance obligations if the product is sold with delivery. In these instances, delivery most often occurs on the same day as the control of the product transfers to the customer. As a result, even in the case of multiple performance obligations, the performance obligations are satisfied concurrently and revenue is recognized simultaneously. Services We earn revenue from the provision of services, which are primarily paving and related services, but also include landfill operations and the receipt and disposal of waste that is converted to fuel for use in our cement plants. Revenue from the receipt of waste fuels is recognized when the waste is accepted and a corresponding liability is recognized for the costs to process the waste into fuel for the manufacturing of cement or to ship the waste offsite for disposal in accordance with applicable regulations. Collectability of service contracts is due reasonably after certain milestones in the contract are performed. Milestones vary by project, but are typically calculated using monthly progress based on the percentage of completion or a customer’s engineer review of progress. The majority of the time, collection occurs within 90 days of billing and cash is received within the same fiscal year as services performed. On most projects, the customer will withhold a portion of the invoice for retainage, which may last longer than a year depending on the job. Revenue derived from paving and related services is recognized over time based on the proportion of costs incurred to date relative to the total estimated costs at completion, which approximates progress towards completion. Under this method, we recognize paving and related services revenue as services are rendered. The majority of our construction service contracts are completed within one year, but may occasionally extend beyond this time frame. The majority of our construction service contracts, and therefore, revenue, are opened and completed within one year, with most activity during the spring, summer and fall. We estimate profit as the difference between total estimated revenue and total estimated cost of a contract and recognize that profit over the life of the contract based on input measures. We generally measure progress toward completion on long- term paving and related services contracts based on the proportion of costs incurred to date relative to total estimated costs at completion. We include revisions of estimated profits on contracts in earnings under the cumulative catch-up method, under which the effect of revisions in estimates is recognized immediately. If a revised estimate of contract profitability reveals an anticipated loss on the contract, we recognize the loss in the period it is identified. The actual cost to total estimated cost method of accounting involves the use of various estimating techniques to project costs at completion, and in some cases includes estimates of recoveries asserted against the customer for changes in specifications or other disputes. Contract estimates involve various assumptions and projections relative to the outcome of future events over multiple periods, including future labor productivity and availability, the nature and complexity of the work to be performed, the cost and availability of materials, the effect of delayed performance, and the availability and timing of funding from the customer. These estimates are based on our best judgment. A significant change in one or more of these estimates could affect the profitability of one or more of our contracts. We review our contract estimates regularly to assess revisions in contract values and estimated costs at completion. Inherent uncertainties in estimating costs make it at least reasonably possible that the estimates used will change within the near term and over the life of the contracts. No material adjustments to a contract were recognized in the year ended January 2, 2021. We recognize claims when the amount of the claim can be estimated reliably and it is legally enforceable. In evaluating these criteria, we consider the contractual basis for the claim, the cause of any additional costs incurred, the reasonableness of those costs and the objective evidence available to support the claim. When the contract includes variable consideration, we estimate the amount of consideration to which we will be entitled in exchange for transferring the promised goods or services to a customer. The amount of estimated variable consideration included in the transaction price is the amount for which it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Types of variable consideration include, but are not limited to, liquidated damages and other performance penalties and production and placement bonuses. The majority of contract modifications relate to the original contract and are often an extension of the original performance obligation. Predominately, modifications are not distinct from the terms in the original contract; therefore, they are considered part of a single performance obligation. We account for the modification using a cumulative catch-up adjustment. However, there are instances where goods or services in a modification are distinct from those transferred prior to the modification. In these situations, we account for the modifications as either a separate contract or prospectively depending on the facts and circumstances of the modification. Generally, construction contracts contain mobilization costs which are categorized as costs to fulfill a contract. These costs are excluded from any measure of progress toward contract fulfillment. These costs do not result in the transfer of control of a good or service to the customer and are amortized over the life of the contract. Costs and estimated earnings in excess of billings are composed principally of revenue recognized on contracts on the percentage of completion method for which billings had not been presented to customers because the amounts were not billable under the contract terms at the balance sheet date. In accordance with the contract terms, the unbilled receivables at the balance sheet date are expected to be billed in following periods. Billings in excess of costs and estimated earnings represent billings in excess of revenue recognized.
Inventories	Inventories —Inventories consist of stone that has been removed from quarries and processed for future sale, cement, raw materials and finished concrete blocks. Inventories are valued at the lower of cost or net realizable value and are accounted for on a first-in first-out basis or an average cost basis. If items become obsolete or otherwise unusable or if quantities exceed what is projected to be sold within a reasonable period of time, they will be charged to costs of revenue in the period that the items are designated as obsolete or excess inventory. Stripping costs are costs of removing overburden and waste material to access aggregate materials and are expensed as incurred.
Property, Plant and Equipment, net	Property, Plant and Equipment, net —Property, plant and equipment are recorded at cost, less accumulated depreciation, depletion and amortization. Expenditures for additions and improvements that significantly add to the productive capacity or extend the useful life of an asset are capitalized. Repair and maintenance costs that do not substantially expand productive capacity or extend the life of property, plant and equipment are expensed as incurred. Landfill airspace is included in property, plant and equipment at cost and is amortized based on the portion of the airspace used during the period compared to the gross estimated value of available airspace, which is updated periodically as circumstances dictate. Management reassesses the landfill airspace capacity with any changes in value recorded in cost of revenue. Capitalized landfill costs include expenditures for the acquisition of land and related airspace, engineering and permitting costs, cell construction costs and direct site improvement costs. Upon disposal of an asset, the cost and related accumulated depreciation are removed from the Company’s accounts and any gain or loss is included in general and administrative expenses. The Company reviews the carrying value of property, plant and equipment for impairment whenever events or circumstances indicate that the carrying value of an asset may not be recoverable from the estimated future cash flows expected to result from its use and eventual disposition. Such indicators may include, among others, deterioration in general economic conditions, adverse changes in the markets in which an entity operates, increases in input costs that have a negative effect on earnings and cash flows or a trend of negative or declining cash flows over multiple periods. Property, plant and equipment is tested for impairment at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets. As a result, the property, plant and equipment impairment test is at a significantly lower level than the level at which goodwill is tested for impairment. In markets where the Company does not produce downstream products, such as ready-mix concrete, asphalt paving mix and paving and related services, the lowest level of largely independent identifiable cash flows is at the individual aggregates operation or a group of aggregates operations collectively serving a local market or the cement operations. Conversely, in vertically-integrated markets, the cash flows of the downstream and upstream businesses are not largely independently identifiable and the vertically-integrated operations are considered the lowest level of largely independent identifiable cash flows. Aggregates mineral bearing land and interests are included in property, plant and equipment. When leased mineral interests are acquired during a business combination, they are valued using an excess earnings approach for the life of the proven and probable reserves. Depletion expense is recorded using a units of production methodology.
Accrued Mining and Landfill Reclamation	Accrued Mining and Landfill Reclamation —The mining reclamation reserve and financial commitments for landfill closure and post-closure activities are based on management’s estimate of future cost requirements to reclaim property at both currently operating and closed sites. Estimates of these obligations have been developed based on management’s interpretation of current requirements and proposed regulatory changes and are intended to approximate fair value. Costs are estimated in current dollars, inflated until the expected time of payment, and then discounted back to present value using a credit-adjusted risk-free rate on obligations of similar maturity, adjusted to reflect the Company’s credit rating. Changes in the credit-adjusted risk-free rate do not change recorded liabilities. However, subsequent increases in the recognized obligations are measured using a current credit-adjusted risk-free rate. Decreases in the recognized obligations are measured at the initial credit-adjusted risk-free rate. Significant changes in inflation rates, or the amount or, timing of future cost estimates typically result in both (1) a current adjustment to the recorded liability (and corresponding adjustment to the asset) and (2) a change in accretion of the liability and depreciation of the asset to be recorded prospectively over the remaining capacity of the unmined quarry or landfill.
Goodwill	Goodwill —Goodwill represents the purchase price paid in excess of the fair value of net tangible and intangible assets acquired. Goodwill recorded in connection with the Company’s acquisitions is primarily attributable to the expected profitability, assembled workforces of the acquired businesses and the synergies expected to arise after the Company’s acquisition of those businesses. Goodwill is not amortized, but is tested annually for impairment as of the first day of the fourth quarter and at any time that events or circumstances indicate that goodwill may be impaired. A qualitative approach may first be applied to determine whether it is more likely than not that the estimated fair value of a reporting unit is less than its carrying amount. If, as a result of the qualitative assessment, it is determined that an impairment is more likely than not, the two-step quantitative impairment test is then performed, otherwise further analysis is not required. The two-step impairment test first identifies potential goodwill impairment for each reporting unit and then, if necessary, measures the amount of the impairment loss.
Income Taxes	Income Taxes —Summit Inc. is a corporation subject to income taxes in the United States. Certain subsidiaries, including Summit Holdings, or subsidiary groups of the Company are taxable separate from Summit Inc. The provision for income taxes, or Summit Inc.’s proportional share of the provision, are included in the Company’s consolidated financial statements. The Company’s deferred income tax assets and liabilities are computed for differences between the tax basis and financial statement amounts that will result in taxable or deductible amounts in the future. The computed deferred balances are based on enacted tax laws and applicable rates for the periods in which the differences are expected to affect taxable income. A valuation allowance is recognized for deferred tax assets if it is more likely than not that some portion or all of the net deferred tax assets will not be realized. In making such a determination, all available positive and negative evidence is considered, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines it would be able to realize its deferred tax assets for which a valuation allowance had been recorded then an adjustment would be made to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company evaluates the tax positions taken on income tax returns that remain open and positions expected to be taken on the current year tax returns to identify uncertain tax positions. Unrecognized tax benefits on uncertain tax positions are recorded on the basis of a two-step process in which (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the largest amount of tax benefit that is more than 50 percent likely to be realized is recognized. Interest and penalties related to unrecognized tax benefits are recorded in income tax expense (benefit).
Tax Receivable Agreement	Tax Receivable Agreement — When Class A limited partnership units of Summit Holdings (“LP Units”) are exchanged for shares of Class A common stock of Summit Inc. or Summit Inc. purchases LP Units for cash, this results in increases in Summit Inc.’s share of the tax basis of the tangible and intangible assets, which increases the tax depreciation and amortization deductions that otherwise would not have been available to Summit Inc. These increases in tax basis and tax depreciation and amortization deductions are expected to reduce the amount of cash taxes that we would otherwise be required to pay in the future. Prior to our IPO, we entered into a TRA with the pre-IPO owners that requires us to pay the pre-IPO owners or their permitted assignees 85% of the amount of cash savings, if any, in U.S. federal, state, and local income tax that we actually realize as a result of these exchanges. These benefits include (1) increases in the tax basis of tangible and intangible assets of Summit Holdings and certain other tax benefits related to entering into the TRA, (2) tax benefits attributable to payments under the TRA, or (3) under certain circumstances such as an early termination of the TRA, we are deemed to realize, as a result of the increases in tax basis in connection with exchanges by the pre-IPO owners described above and certain other tax benefits attributable to payments under the TRA. As noted above, we periodically evaluate the realizability of the deferred tax assets resulting from the exchange of LP Units for Class A common stock. If the deferred tax assets are determined to be realizable, we then assess whether payment of amounts under the TRA have become probable. If so, we record a TRA liability equal to 85% of such deferred tax assets. In subsequent periods, we assess the realizability of all of our deferred tax assets subject to the TRA. Should we determine a deferred tax asset with a valuation allowance is realizable in a subsequent period, the related valuation allowance will be released and consideration of a corresponding TRA liability will be assessed. The realizability of deferred tax assets, including those subject to the TRA, is dependent upon the generation of future taxable income during the periods in which those deferred tax assets become deductible and consideration of prudent and feasible tax-planning strategies. The measurement of the TRA liability is accounted for as a contingent liability. Therefore, once we determine that a payment to a pre-IPO owner has become probable and can be estimated, the estimate of payment will be accrued.
Earnings per Share	Earnings per Share— The Company computes basic earnings per share attributable to stockholders by dividing income attributable to Summit Inc. by the weighted-average shares of Class A common stock outstanding. Diluted earnings per share reflects the potential dilution beyond shares for basic earnings per share that could occur if securities or other contracts to issue common stock were exercised, converted into common stock, or resulted in the issuance of common stock that would have shared in the Company’s earnings. Since the Class B common stock has no economic value, those shares are not included in the weighted-average common share amount for basic or diluted earnings per share. In addition, as the shares of Class A common stock are issued by Summit Inc., the earnings and equity interests of noncontrolling interests are not included in basic earnings per share.
New Accounting Standards	New Accounting Standards — In February 2016, the Financial Accounting Standards Board FASB ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet. Lessees are required to disclose more quantitative and qualitative information about the leases than current U.S. GAAP requires. The ASU and subsequent amendments issued in 2018 are effective for public entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We adopted the standard effective December 30, 2018 using the modified retrospective approach. The modified retrospective approach provides a method for recording existing leases at adoption. In addition, we elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed us to carry forward the historical lease classification. In addition, we elected the hindsight practical expedient to determine the lease term for existing leases. The most significant impact upon adoption was the recognition of $36.8 million of operating lease right-of-use assets and $36.8 million operating lease liabilities. The standard had no material impact on our statements of operations and cash flows. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, allowing more financial and nonfinancial hedging strategies to be eligible for hedge accounting. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, increasing the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which reduces the accounting complexity of implementing a cloud computing service arrangement. The ASU aligns the capitalization of implementation costs among hosting arrangements and costs incurred to develop internal-use software. We adopted this ASU in the first quarter of 2020 and the adoption of this ASU did not have a material impact on the consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework Changes to The Disclosure Requirements for Defined Benefits Plans, which modifies the disclosure requirements of employer-sponsored defined benefit and other postretirement benefits plans. The ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results.
Summit Materials, LLC
Company Information
Principles of Consolidation	Principles of Consolidation –The consolidated financial statements include the accounts of Summit LLC and its majority owned subsidiaries. All intercompany balances and transactions have been eliminated. The Company attributes consolidated member’s interest and net income separately to the controlling and noncontrolling interests. Noncontrolling interests in consolidated subsidiaries represent a 20% ownership in Ohio Valley Asphalt, LLC and, prior to the initial public offering (“IPO”) and concurrent purchase of the noncontrolling interests Continental Cement Company, L.L.C. (“Continental Cement”), a 30% redeemable ownership in Continental Cement. The Company accounts for investments in entities for which it has an ownership of 20% to 50% using the equity method of accounting. The Company’s fiscal year is based on a 52-53 week year with each quarter composed of 13 weeks ending on a Saturday. The year ended January 2, 2021 was a 53-week year.
Use of Estimates	Use of Estimates — Preparation of these consolidated financial statements in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) requires management to make estimates and assumptions. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities and reported amounts of revenue and expenses. Such estimates include the valuation of accounts receivable, inventories, valuation of deferred tax assets, goodwill, intangibles and other long-lived assets, pension and other postretirement obligations and asset retirement obligations. Estimates also include revenue earned on contracts and costs to complete contracts. Most of the Company’s paving and related services are performed under fixed unit-price contracts with state and local governmental entities. Management regularly evaluates its estimates and assumptions based on historical experience and other factors, including the current economic environment. As future events and their effects cannot be determined with precision, actual results can differ significantly from estimates made. Changes in estimates, including those resulting from continuing changes in the economic environment, are reflected in the Company’s consolidated financial statements when the change in estimate occurs.
Business and Credit Concentrations	Business and Credit Concentrations— The Company’s operations are conducted primarily across 23 U.S. states and in British Columbia, Canada, with the most significant revenue generated in Texas, Utah, Kansas and Missouri. The Company’s accounts receivable consist primarily of amounts due from customers within these areas. Therefore, collection of these accounts is dependent on the economic conditions in the aforementioned states, as well as specific situations affecting individual customers. Credit granted within the Company’s trade areas has been granted to many customers and management does not
Accounts Receivable	Accounts Receivable —Accounts receivable are stated at the amount management expects to collect from outstanding balances. Management provides for probable uncollectible amounts through a charge to earnings and a credit to a valuation allowance based on its assessment of the collectability of individual accounts. In establishing the allowance, management considers historical losses adjusted to take into account current market conditions and its customers’ financial condition, the amount of receivables in dispute, the current receivables aging and current payment terms. Balances that remain outstanding after reasonable collection efforts are exercised are written off through a charge to the valuation allowance. The balances billed but not paid by customers, pursuant to retainage provisions included in contracts, are generally due upon completion of the contracts.
Revenue Recognition	Revenue Recognition —We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products and plastics components, and from the provision of services, which are primarily paving and related services, but also include landfill operations, the receipt and disposal of waste that is converted to fuel for use in our cement plants. Products We earn revenue from the sale of products, which primarily include aggregates, cement, ready-mix concrete and asphalt, but also include concrete products, net of discounts or allowances, if any, and freight and delivery charges billed to customers. Revenue for product sales is recognized when evidence of an arrangement exists and when control passes, which generally is when the product is shipped. Aggregates and cement products are sold point-of-sale through purchase orders. When the product is sold on account, collectability typically occurs 30 to 60 days after the sale. Revenue is recognized when cash is received from the customer at the point of sale or when the products are delivered or collected on site. There are no other timing implications that will create a contract asset or liability, and contract modifications are unlikely given the timing and nature of the transaction. Material sales are likely to have multiple performance obligations if the product is sold with delivery. In these instances, delivery most often occurs on the same day as the control of the product transfers to the customer. As a result, even in the case of multiple performance obligations, the performance obligations are satisfied concurrently and revenue is recognized simultaneously. Services We earn revenue from the provision of services, which are primarily paving and related services, but also include landfill operations and the receipt and disposal of waste that is converted to fuel for use in our cement plants. Revenue from the receipt of waste fuels is recognized when the waste is accepted and a corresponding liability is recognized for the costs to process the waste into fuel for the manufacturing of cement or to ship the waste offsite for disposal in accordance with applicable regulations. Collectability of service contracts is due reasonably after certain milestones in the contract are performed. Milestones vary by project, but are typically calculated using monthly progress based on the percentage of completion or a customer’s engineer review of progress. The majority of the time, collection occurs within 90 days of billing and cash is received within the same fiscal year as services performed. On most projects, the customer will withhold a portion of the invoice for retainage, which may last longer than a year depending on the job. Revenue derived from paving and related services is recognized over time based on the proportion of costs incurred to date relative to the total estimated costs at completion, which approximates progress towards completion. Under this method, we recognize paving and related services revenue as services are rendered. The majority of our construction service contracts are completed within one year, but may occasionally extend beyond this time frame. The majority of our construction service contracts, and therefore, revenue, are opened and completed within one year, with most activity during the spring, summer and fall. We estimate profit as the difference between total estimated revenue and total estimated cost of a contract and recognize that profit over the life of the contract based on input measures. We generally measure progress toward completion on long-term paving and related services contracts based on the proportion of costs incurred to date relative to total estimated costs at completion. We include revisions of estimated profits on contracts in earnings under the cumulative catch-up method, under which the effect of revisions in estimates is recognized immediately. If a revised estimate of contract profitability reveals an anticipated loss on the contract, we recognize the loss in the period it is identified. The actual cost to total estimated cost method of accounting involves the use of various estimating techniques to project costs at completion, and in some cases includes estimates of recoveries asserted against the customer for changes in specifications or other disputes. Contract estimates involve various assumptions and projections relative to the outcome of future events over multiple periods, including future labor productivity and availability, the nature and complexity of the work to be performed, the cost and availability of materials, the effect of delayed performance, and the availability and timing of funding from the customer. These estimates are based on our best judgment. A significant change in one or more of these estimates could affect the profitability of one or more of our contracts. We review our contract estimates regularly to assess revisions in contract values and estimated costs at completion. Inherent uncertainties in estimating costs make it at least reasonably possible that the estimates used will change within the near term and over the life of the contracts. No material adjustments to a contract were recognized in the year ended January 2, 2021. We recognize claims when the amount of the claim can be estimated reliably and it is legally enforceable. In evaluating these criteria, we consider the contractual basis for the claim, the cause of any additional costs incurred, the reasonableness of those costs and the objective evidence available to support the claim. When the contract includes variable consideration, we estimate the amount of consideration to which we will be entitled in exchange for transferring the promised goods or services to a customer. The amount of estimated variable consideration included in the transaction price is the amount for which it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Types of variable consideration include, but are not limited to, liquidated damages and other performance penalties and production and placement bonuses. The majority of contract modifications relate to the original contract and are often an extension of the original performance obligation. Predominately, modifications are not distinct from the terms in the original contract; therefore, they are considered part of a single performance obligation. We account for the modification using a cumulative catch-up adjustment. However, there are instances where goods or services in a modification are distinct from those transferred prior to the modification. In these situations, we account for the modifications as either a separate contract or prospectively depending on the facts and circumstances of the modification. Generally, construction contracts contain mobilization costs which are categorized as costs to fulfill a contract. These costs are excluded from any measure of progress toward contract fulfillment. These costs do not result in the transfer of control of a good or service to the customer and are amortized over the life of the contract. Costs and estimated earnings in excess of billings are composed principally of revenue recognized on contracts on the percentage of completion method for which billings had not been presented to customers because the amounts were not billable under the contract terms at the balance sheet date. In accordance with the contract terms, the unbilled receivables at the balance sheet date are expected to be billed in following periods. Billings in excess of costs and estimated earnings represent billings in excess of revenue recognized.
Inventories	Inventories —Inventories consist of stone that has been removed from quarries and processed for future sale, cement, raw materials and finished concrete blocks. Inventories are valued at the lower of cost or net realizable value and are accounted for on a first-in first-out basis or an average cost basis. If items become obsolete or otherwise unusable or if quantities exceed what is projected to be sold within a reasonable period of time, they will be charged to costs of revenue in the period that the items are designated as obsolete or excess inventory. Stripping costs are costs of removing overburden and waste material to access aggregate materials and are expensed as incurred.
Property, Plant and Equipment, net	Property, Plant and Equipment, net —Property, plant and equipment are recorded at cost, less accumulated depreciation, depletion and amortization. Expenditures for additions and improvements that significantly add to the productive capacity or extend the useful life of an asset are capitalized. Repair and maintenance costs that do not substantially expand productive capacity or extend the life of property, plant and equipment are expensed as incurred. Landfill airspace is included in property, plant and equipment at cost and is amortized based on the portion of the airspace used during the period compared to the gross estimated value of available airspace, which is updated periodically as circumstances dictate. Management reassesses the landfill airspace capacity with any changes in value recorded in cost of revenue. Capitalized landfill costs include expenditures for the acquisition of land and related airspace, engineering and permitting costs, cell construction costs and direct site improvement costs. Upon disposal of an asset, the cost and related accumulated depreciation are removed from the Company’s accounts and any gain or loss is included in general and administrative expenses. The Company reviews the carrying value of property, plant and equipment for impairment whenever events or circumstances indicate that the carrying value of an asset may not be recoverable from the estimated future cash flows expected to result from its use and eventual disposition. Such indicators may include, among others, deterioration in general economic conditions, adverse changes in the markets in which an entity operates, increases in input costs that have a negative effect on earnings and cash flows or a trend of negative or declining cash flows over multiple periods. Property, plant and equipment is tested for impairment at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets. As a result, the property, plant and equipment impairment test is at a significantly lower level than the level at which goodwill is tested for impairment. In markets where the Company does not produce downstream products, such as ready-mix concrete, asphalt paving mix and paving and related services, the lowest level of largely independent identifiable cash flows is at the individual aggregates operation or a group of aggregates operations collectively serving a local market or the cement operations. Conversely, in vertically-integrated markets, the cash flows of the downstream and upstream businesses are not largely independently identifiable and the vertically-integrated operations are considered the lowest level of largely independent identifiable cash flows. Aggregates mineral bearing land and interests are included in property, plant and equipment. When leased mineral interests are acquired during a business combination, they are valued using an excess earnings approach for the life of the proven and probable reserves. Depletion expense is recorded using a units of production methodology.
Accrued Mining and Landfill Reclamation	Accrued Mining and Landfill Reclamation —The mining reclamation reserve and financial commitments for landfill closure and post-closure activities are based on management’s estimate of future cost requirements to reclaim property at both currently operating and closed sites. Estimates of these obligations have been developed based on management’s interpretation of current requirements and proposed regulatory changes and are intended to approximate fair value. Costs are estimated in current dollars, inflated until the expected time of payment, and then discounted back to present value using a credit-adjusted risk-free rate on obligations of similar maturity, adjusted to reflect the Company’s credit rating. Changes in the credit-adjusted risk-free rate do not change recorded liabilities. However, subsequent increases in the recognized obligations are measured using a current credit-adjusted risk-free rate. Decreases in the recognized obligations are measured at the initial credit-adjusted risk-free rate. Significant changes in inflation rates, or the amount or, timing of future cost estimates typically result in both (1) a current adjustment to the recorded liability (and corresponding adjustment to the asset) and (2) a change in accretion of the liability and depreciation of the asset to be recorded prospectively over the remaining capacity of the unmined quarry or landfill.
Goodwill	Goodwill —Goodwill represents the purchase price paid in excess of the fair value of net tangible and intangible assets acquired. Goodwill recorded in connection with the Company’s acquisitions is primarily attributable to the expected profitability, assembled workforces of the acquired businesses and the synergies expected to arise after the Company’s acquisition of those businesses. Goodwill is not amortized, but is tested annually for impairment as of the first day of the fourth quarter and at any time that events or circumstances indicate that goodwill may be impaired. A qualitative approach may first be applied to determine whether it is more likely than not that the estimated fair value of a reporting unit is less than its carrying amount. If, as a result of the qualitative assessment, it is determined that an impairment is more likely than not, the two-step quantitative impairment test is then performed, otherwise further analysis is not required. The two-step impairment test first identifies potential goodwill impairment for each reporting unit and then, if necessary, measures the amount of the impairment loss.
Income Taxes	Income Taxes —As a limited liability company, the Company’s federal and state income tax attributes are generally passed to its member. However, certain subsidiaries, or subsidiary groups, of the Company are taxable entities subject to income taxes in the United States and Canada, the provisions for which are included in the consolidated financial statements. Significant judgments and estimates are required in the determination of the consolidated income tax expense. The Company’s deferred income tax assets and liabilities are computed for differences between the tax basis and financial statement amounts that will result in taxable or deductible amounts in the future. The computed deferred balances are based on enacted tax laws and applicable rates for the periods in which the differences are expected to affect taxable income. A valuation allowance is recognized for deferred tax assets if it is more likely than not that some portion or all of the net deferred tax assets will not be realized. In making such a determination, all available positive and negative evidence is considered, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines it would be able to realize its deferred tax assets for which a valuation allowance had been recorded then an adjustment would be made to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company evaluates the tax positions taken on income tax returns that remain open and positions expected to be taken on the current year tax returns to identify uncertain tax positions. Unrecognized tax benefits on uncertain tax positions are recorded on the basis of a two-step process in which (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the largest amount of tax benefit that is more than 50 percent likely to be realized is recognized. Interest and penalties related to unrecognized tax benefits are recorded in income tax expense (benefit).
New Accounting Standards	New Accounting Standards — In February 2016, the Financial Accounting Standards Board FASB ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet. Lessees are required to disclose more quantitative and qualitative information about the leases than current U.S. GAAP requires. The ASU and subsequent amendments issued in 2018 are effective for public entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. We adopted the standard effective December 30, 2018 using the modified retrospective approach. The modified retrospective approach provides a method for recording existing leases at adoption. In addition, we elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed us to carry forward the historical lease classification. In addition, we elected the hindsight practical expedient to determine the lease term for existing leases. The most significant impact upon adoption was the recognition of $36.8 million of operating lease right-of-use assets and $36.8 million operating lease liabilities. The standard had no material impact on our statements of operations and cash flows. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, allowing more financial and nonfinancial hedging strategies to be eligible for hedge accounting. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, increasing the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The ASU is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results. In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which reduces the accounting complexity of implementing a cloud computing service arrangement. The ASU aligns the capitalization of implementation costs among hosting arrangements and costs incurred to develop internal-use software. We adopted this ASU in the first quarter of 2020 and the adoption of this ASU did not have a material impact on the consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework Changes to The Disclosure Requirements for Defined Benefits Plans, which modifies the disclosure requirements of employer-sponsored defined benefit and other postretirement benefits plans. The ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years. The adoption of this new ASU did not have a material impact on our consolidated financial results.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Jan. 02, 2021
Summary of Acquisitions by Region	The following table summarizes the Company’s acquisitions by region and year: 2020 2019 2018 West 2 2 5 East (1) 1 — 7 ______________________ (1) In addition, the Company acquired certain assets of a small ready-mix concrete operation in the second quarter of 2018.
Summary of Assets Acquired and Liabilities Assumed	The table below summarizes aggregated information regarding the fair values of the assets acquired and liabilities assumed as of the respective acquisition dates. 2020 2019 Financial assets $ 8,696 $ — Inventories 2,856 52 Property, plant and equipment 130,042 3,542 Other assets 2,790 — Financial liabilities (4,469) (36) Other long-term liabilities (16,069) — Net assets acquired 123,846 3,558 Goodwill — 1,834 Purchase price 123,846 5,392 Other (369) — Net cash paid for acquisitions $ 123,477 $ 5,392
Schedule of remaining payments under noncompete and deferred consideration agreements	The remaining payments due under these noncompete and deferred consideration agreements are as follows: 2021 $ 9,705 2022 3,411 2023 2,657 2024 2,620 2025 2,567 Thereafter 4,454 Total scheduled payments 25,414 Present value adjustments (4,766) Total noncompete obligations and deferred consideration $ 20,648
Summit Materials, LLC
Summary of Acquisitions by Region	The following table summarizes the Company’s acquisitions by region and year: 2020 2019 2018 West 2 2 5 East (1) 1 — 7 ______________________ (1) In addition, the Company acquired certain assets of a small ready-mix concrete operation in the second quarter of 2018.
Summary of Assets Acquired and Liabilities Assumed	The table below summarizes aggregated information regarding the fair values of the assets acquired and liabilities assumed as of the respective acquisition dates. 2020 2019 Financial assets $ 8,696 $ — Inventories 2,856 52 Property, plant and equipment 130,042 3,542 Other assets 2,790 — Financial liabilities (4,469) (36) Other long-term liabilities (16,069) — Net assets acquired 123,846 3,558 Goodwill — 1,834 Purchase price 123,846 5,392 Other (369) — Net cash paid for acquisitions $ 123,477 $ 5,392
Schedule of remaining payments under noncompete and deferred consideration agreements	The remaining payments due under these noncompete and deferred consideration agreements are as follows: 2021 $ 7,205 2022 3,411 2023 2,657 2024 2,620 2025 2,567 Thereafter 4,454 Total scheduled payments 22,914 Present value adjustments (4,704) Total noncompete obligations and deferred consideration $ 18,210

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Jan. 02, 2021
Goodwill by Reportable Segment and in Total	The following table presents goodwill by reportable segments and in total: West East Cement Total Balance—December 29, 2018 $ 580,567 $ 406,805 $ 204,656 $ 1,192,028 Acquisitions 1,657 3,621 — 5,278 Foreign currency translation adjustments 2,393 — — 2,393 Balance—December 28, 2019 $ 584,617 $ 410,426 $ 204,656 $ 1,199,699 Acquisitions (1) 19 — — 19 Foreign currency translation adjustments 1,573 — — 1,573 Balance—January 2, 2021 $ 586,209 $ 410,426 $ 204,656 $ 1,201,291 ______________________ (1) Reflects goodwill from 2020 acquisitions and working capital adjustments from prior year acquisitions.
Summit Materials, LLC
Goodwill by Reportable Segment and in Total	The following table presents goodwill by reportable segments and in total: West East Cement Total Balance—December 29, 2018 $ 581,567 $ 406,805 $ 204,656 $ 1,193,028 Acquisitions 1,657 3,621 — 5,278 Foreign currency translation adjustments 2,393 — — 2,393 Balance—December 28, 2019 $ 585,617 $ 410,426 $ 204,656 $ 1,200,699 Acquisitions (1) 19 — — 19 Foreign currency translation adjustments 1,573 — — 1,573 Balance—January 2, 2021 $ 587,209 $ 410,426 $ 204,656 $ 1,202,291 ______________________ (1) Reflects goodwill from 2020 acquisitions and working capital adjustments from prior year acquisitions.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Jan. 02, 2021
Revenue from External Customer [Line Items]
Summary of Revenue by Products	Revenue by product for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 consisted of the following: 2020 2019 2018 Revenue by product*: Aggregates $ 498,007 $ 469,670 $ 373,824 Cement 257,629 266,235 258,876 Ready-mix concrete 668,060 607,622 584,114 Asphalt 349,350 330,750 301,247 Paving and related services 381,430 360,234 379,540 Other 177,975 187,629 203,401 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ * Revenue from the liquid asphalt terminals is included in asphalt revenue.
Summary of Contract Assets and Liabilities	The following table outlines the significant changes in contract assets and contract liability balances from December 28, 2019 to January 2, 2021. Also included in the table is the net change in the estimate as a percentage of aggregate revenue for such contracts: Costs and estimated Billings in excess earnings in of costs and excess of billings estimated earnings Balance—December 28, 2019 $ 13,088 $ 13,864 Changes in revenue billed, contract price or cost estimates (4,535) 2,616 Other 113 19 Balance—January 2, 2021 $ 8,666 $ 16,499
Summary of Accounts Receivable, Net	Accounts receivable, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Trade accounts receivable $ 191,871 $ 191,672 Construction contract receivables 47,179 47,966 Retention receivables 18,824 17,808 Receivables from related parties 1,339 1,596 Accounts receivable 259,213 259,042 Less: Allowance for doubtful accounts (4,517) (5,786) Accounts receivable, net $ 254,696 $ 253,256
Summit Materials, LLC
Revenue from External Customer [Line Items]
Summary of Revenue by Products	Revenue by product for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 consisted of the following: 2020 2019 2018 Revenue by product*: Aggregates $ 498,007 $ 469,670 $ 373,824 Cement 257,629 266,235 258,876 Ready-mix concrete 668,060 607,622 584,114 Asphalt 349,350 330,750 301,247 Paving and related services 381,430 360,234 379,540 Other 177,975 187,629 203,401 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ *Revenue from the liquid asphalt terminals is included in asphalt revenue.
Summary of Contract Assets and Liabilities	The following table outlines the significant changes in contract assets and contract liability balances from December 28, 2019 to January 2, 2021. Also included in the table is the net change in the estimate as a percentage of aggregate revenue for such contracts: Costs and estimated Billings in excess earnings in of costs and excess of billings estimated earnings Balance—December 28, 2019 $ 13,088 $ 13,864 Changes in revenue billed, contract price or cost estimates (4,535) 2,616 Other 113 19 Balance—January 2, 2021 $ 8,666 $ 16,499
Summary of Accounts Receivable, Net	Accounts receivable, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Trade accounts receivable $ 191,871 $ 191,672 Construction contract receivables 47,179 47,966 Retention receivables 18,824 17,808 Receivables from related parties 1,339 1,596 Accounts receivable 259,213 259,042 Less: Allowance for doubtful accounts (4,517) (5,786) Accounts receivable, net $ 254,696 $ 253,256

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Jan. 02, 2021
Inventory [Line Items]
Components of Inventories	Inventories consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Aggregate stockpiles $ 137,938 $ 140,461 Finished goods 32,993 33,023 Work in process 9,281 7,664 Raw materials 20,096 23,639 Total $ 200,308 $ 204,787
Summit Materials, LLC
Inventory [Line Items]
Components of Inventories	Inventories consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Aggregate stockpiles $ 137,938 $ 140,461 Finished goods 32,993 33,023 Work in process 9,281 7,664 Raw materials 20,096 23,639 Total $ 200,308 $ 204,787

Property, Plant and Equipment_2

Property, Plant and Equipment, net and Intangibles, net (Tables)	12 Months Ended
	Jan. 02, 2021
Property, Plant and Equipment [Line Items]
Summary of Property, Plant and Equipment	Property, plant and equipment, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Mineral bearing land and leased interests $ 468,966 $ 333,024 Land (non-mineral bearing) 197,432 182,065 Buildings and improvements 181,198 178,088 Plants, machinery and equipment 1,397,410 1,318,512 Mobile equipment and barges 543,133 501,809 Truck and auto fleet 56,163 54,838 Landfill airspace and improvements 52,202 49,766 Office equipment 45,942 43,155 Construction in progress 40,648 42,007 Property, plant and equipment 2,983,094 2,703,264 Less accumulated depreciation, depletion and amortization (1,132,925) (955,815) Property, plant and equipment, net $ 1,850,169 $ 1,747,449 Buildings and improvements 10 - 30 years Plant, machinery and equipment 7 - 20 years Office equipment 3 - 7 years Truck and auto fleet 5 - 8 years Mobile equipment and barges 6 - 8 years Landfill airspace and improvements 10 - 30 years Other 4 - 20 years
Intangible Assets by Type and in Total	The following table shows intangible assets by type and in total: January 2, 2021 December 28, 2019 Gross Net Gross Net Carrying Accumulated Carrying Carrying Accumulated Carrying Amount Amortization Amount Amount Amortization Amount Operating permits $ 33,671 $ (1,207) $ 32,464 $ 6,609 $ (290) $ 6,319 Mineral leases 19,225 (7,571) 11,654 19,064 (6,408) 12,656 Reserve rights 6,234 (2,504) 3,730 6,234 (2,248) 3,986 Trade names — — — 1,000 (958) 42 Other 586 (582) 4 957 (462) 495 Total intangible assets $ 59,716 $ (11,864) $ 47,852 $ 33,864 $ (10,366) $ 23,498
Estimated Amortization Expense for Intangible Assets	The estimated amortization expense for intangible assets for each of the next five years and thereafter is as follows: 2021 $ 3,129 2022 3,136 2023 3,003 2024 2,908 2025 2,863 Thereafter 32,813 Total $ 47,852
Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Summary of Property, Plant and Equipment	Property, plant and equipment, net consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Mineral bearing land and leased interests $ 468,966 $ 333,024 Land (non-mineral bearing) 197,432 182,065 Buildings and improvements 181,198 178,088 Plants, machinery and equipment 1,397,410 1,318,512 Mobile equipment and barges 543,133 501,809 Truck and auto fleet 56,163 54,838 Landfill airspace and improvements 52,202 49,766 Office equipment 45,942 43,155 Construction in progress 40,648 42,007 Property, plant and equipment 2,983,094 2,703,264 Less accumulated depreciation, depletion and amortization (1,132,925) (955,815) Property, plant and equipment, net $ 1,850,169 $ 1,747,449 Buildings and improvements 10 - 30 years Plant, machinery and equipment 7 - 20 years Office equipment 3 - 7 years Truck and auto fleet 5 - 8 years Mobile equipment and barges 6 - 8 years Landfill airspace and improvements 10 - 30 years Other 4 - 20 years
Intangible Assets by Type and in Total	: January 2, 2021 December 28, 2019 Gross Net Gross Net Carrying Accumulated Carrying Carrying Accumulated Carrying Amount Amortization Amount Amount Amortization Amount Operating permits $ 33,671 $ (1,207) $ 32,464 $ 6,609 $ (290) $ 6,319 Mineral leases 19,225 (7,571) 11,654 19,064 (6,408) 12,656 Reserve rights 6,234 (2,504) 3,730 6,234 (2,248) 3,986 Trade names — — — 1,000 (958) 42 Other 586 (582) 4 957 (462) 495 Total intangible assets $ 59,716 $ (11,864) $ 47,852 $ 33,864 $ (10,366) $ 23,498
Estimated Amortization Expense for Intangible Assets	The estimated amortization expense for intangible assets for each of the next five years and thereafter is as follows: 2021 $ 3,129 2022 3,136 2023 3,003 2024 2,908 2025 2,863 Thereafter 32,813 Total $ 47,852

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Jan. 02, 2021
Schedule Of Accrued Expenses [Line Items]
Components of Accrued Expenses	Accrued expenses consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Interest $ 21,860 $ 26,892 Payroll and benefits 46,026 29,356 Finance lease obligations 24,601 16,007 Insurance 18,355 14,968 Non-income taxes 15,669 7,666 Deferred asset purchase payments 9,749 3,525 Professional fees 828 902 Other (1) 23,482 20,689 Total $ 160,570 $ 120,005 ______________________ (1) Consists primarily of current portion of asset retirement obligations and miscellaneous accruals.
Summit Materials, LLC
Schedule Of Accrued Expenses [Line Items]
Components of Accrued Expenses	Accrued expenses consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Interest $ 21,860 $ 26,892 Payroll and benefits 46,026 29,356 Finance lease obligations 24,601 16,007 Insurance 18,355 14,968 Non-income taxes 15,900 7,898 Deferred asset purchase payments 9,749 3,525 Professional fees 828 902 Other (1) 23,482 20,689 Total $ 160,801 $ 120,237 ______________________ (1) Consists primarily of current portion of asset retirement obligations and miscellaneous accruals.

Debt (Tables)

Debt (Tables)	12 Months Ended
	Jan. 02, 2021
Schedule of Debt	Debt consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Term Loan, due 2024: $616.3 million and $624.3 million, net of $0.9 million and $1.1 million discount at January 2, 2021 and December 28, 2019, respectively $ 615,425 $ 623,140 6 1⁄8% Senior Notes, due 2023: $650.0 million, net of $0.9 million discount at December 28, 2019 — 649,133 5 1⁄8% Senior Notes, due 2025 300,000 300,000 6 1⁄2% Senior Notes, due 2027 300,000 300,000 5 1⁄4% Senior Notes, due 2029 700,000 — Total 1,915,425 1,872,273 Current portion of long-term debt 6,354 7,942 Long-term debt $ 1,909,071 $ 1,864,331
Schedule of Contractual Payments of Long-Term Debt	The contractual payments of long-term debt, including current maturities, for the five years subsequent to January 2, 2021, are as follows: 2021 $ 6,354 2022 6,354 2023 6,354 2024 597,252 2025 300,000 Thereafter 1,000,000 Total 1,916,314 Less: Original issue net discount (889) Less: Capitalized loan costs (16,724) Total debt $ 1,898,701
Summary of Activity for Deferred Financing Fees	The following table presents the activity for the deferred financing fees for the years ended January 2, 2021 and December 28, 2019: Deferred financing fees Balance—December 29, 2018 $ 15,475 Loan origination fees 6,312 Amortization (3,501) Write off of deferred financing fees (2,850) Balance—December 28, 2019 $ 15,436 Loan origination fees 9,605 Amortization (3,336) Write off of deferred financing fees (3,338) Balance—January 2, 2021 $ 18,367
Summit Materials, LLC
Schedule of Debt	Debt consisted of the following as of January 2, 2021 and December 28, 2019: 2020 2019 Term Loan, due 2024: $616.3 million and $624.3 million, net of $0.9 million and $1.1 million discount at January 2, 2021 and December 28, 2019, respectively $ 615,425 $ 623,140 6 1⁄8% Senior Notes, due 2023: $650.0 million, net of $0.9 million discount at December 28, 2019 — 649,133 5 1⁄8% Senior Notes, due 2025 300,000 300,000 6 1⁄2% Senior Notes, due 2027 300,000 300,000 5 1⁄4% Senior Notes, due 2029 700,000 — Total 1,915,425 1,872,273 Current portion of long-term debt 6,354 7,942 Long-term debt $ 1,909,071 $ 1,864,331
Schedule of Contractual Payments of Long-Term Debt	The contractual payments of long-term debt, including current maturities, for the five years subsequent to January 2, 2021, are as follows: 2021 $ 6,354 2022 6,354 2023 6,354 2024 597,252 2025 300,000 Thereafter 1,000,000 Total 1,916,314 Less: Original issue net discount (889) Less: Capitalized loan costs (16,724) Total debt $ 1,898,701
Summary of Activity for Deferred Financing Fees	The following table presents the activity for the deferred financing fees for the years ended January 2, 2021 and December 28, 2019: Deferred financing fees Balance—December 29, 2018 $ 15,475 Loan origination fees 6,312 Amortization (3,501) Write off of deferred financing fees (2,850) Balance—December 28, 2019 $ 15,436 Loan origination fees 9,605 Amortization (3,336) Write off of deferred financing fees (3,338) Balance—January 2, 2021 $ 18,367

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Jan. 02, 2021
Income Taxes [Line Items]
Components of Income Tax Benefit	For the years ended January 2, 2021, December 28, 2019 and December 29, 2018, income taxes consisted of the following: 2020 2019 2018 Provision for income taxes: Current $ 3,827 $ 69 $ 463 Deferred (16,012) 17,032 59,284 Income tax expense (benefit) $ (12,185) $ 17,101 $ 59,747
Schedule of Reconciliation of Income Tax (Benefit) Expense	The effective tax rate on pre-tax income differs from the U.S. statutory rate of 21% for 2020, 2019 and 2018, respectively, due to the following: 2020 2019 2018 Income tax expense (benefit) at federal statutory tax rate $ 27,100 $ 16,427 $ 20,177 Less: Income tax benefit at federal statutory tax rate for LLC entities (593) (658) (561) State and local income taxes 5,067 3,792 4,894 Permanent differences (3,345) (6,272) (5,537) Effective tax rate change 4,257 (2,006) 4,034 Unrecognized tax benefits (41,548) 18,885 22,663 Tax receivable agreement (benefit) expense (6) 2,436 (8,282) Change in valuation allowance — (17,691) 17,592 Other (3,117) 2,188 4,767 Income tax expense (benefit) $ (12,185) $ 17,101 $ 59,747
Components of Net Deferred Income Tax Liability	The following table summarizes the components of the net deferred income tax asset (liability) as January 2, 2021 and December 28, 2019: 2020 2019 Deferred tax assets (liabilities): Net intangible assets $ 199,497 $ 240,790 Accelerated depreciation (209,644) (201,126) Net operating loss 227,560 164,335 Investment in limited partnership (33,139) (31,987) Mining reclamation reserve 3,306 2,018 Working capital (e.g., accrued compensation, prepaid assets) 45,972 37,287 Interest expense limitation carryforward — 2,691 Less valuation allowance (1,675) (1,675) Deferred tax assets 231,877 212,333 Less foreign deferred tax liability (included in other noncurrent liabilities) (18,393) (8,267) Net deferred tax asset $ 213,484 $ 204,066
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: Unrecognized Tax Benefits Balance—December 29, 2018 $ 22,663 Additions based on tax position in 2018 18,885 Balance—December 28, 2019 $ 41,548 Reductions based on new regulations (41,548) Balance—January 2, 2021 $ —
Summary of Valuation Allowance	2020 2019 Valuation Allowance: Beginning balance $ (1,675) $ (19,366) Current year decreases (increases) from operations — 17,691 Ending balance $ (1,675) $ (1,675)
Summit Materials, LLC
Income Taxes [Line Items]
Components of Income Tax Benefit	For the years ended January 2, 2021, December 28, 2019 and December 29, 2018, income taxes consisted of the following: 2020 2019 2018 Provision for income taxes: Current $ 3,827 $ 69 $ 463 Deferred (2,764) 6,316 9,810 Income tax expense (benefit) $ 1,063 $ 6,385 $ 10,273
Schedule of Reconciliation of Income Tax (Benefit) Expense	The effective tax rate on pre-tax income differs from the U.S. statutory rate of 21% for 2020, 2019 and 2018, respectively, due to the following: 2020 2019 2018 Income tax expense (benefit) at federal statutory tax rate $ 25,577 $ 19,947 $ 15,563 Less: Income tax benefit at federal statutory tax rate for LLC entities (17,647) (15,387) (13,863) State and local income taxes 2,073 1,680 1,614 Permanent differences 2,479 13 (1,194) Effective tax rate change 681 (725) (1,148) Unrecognized tax benefits (11,525) 5,038 6,487 Valuation allowance — (2,478) 2,586 Other (575) (1,703) 228 Income tax benefit $ 1,063 $ 6,385 $ 10,273
Components of Net Deferred Income Tax Liability	The following table summarizes the components of the net deferred income tax asset (liability) as January 2, 2021 and December 28, 2019: 2020 2019 Deferred tax (liabilities) assets: Accelerated depreciation $ (70,588) $ (60,216) Net operating loss 26,929 18,036 Investment in limited partnership (18,931) (17,686) Net intangible assets (3,264) (2,554) Mining reclamation reserve 1,652 723 Working capital (e.g., accrued compensation, prepaid assets) 1,590 1,366 Interest expense limitation carryforward — 2,691 Net deferred tax liabilities (62,612) (57,640) Less valuation allowance (1,675) (1,675) Net deferred tax liability $ (64,287) $ (59,315)
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: Unrealized Tax Benefits Balance—December 29, 2018 $ 6,487 Additions based on tax position in 2018 5,132 Balance—December 28, 2019 $ 11,619 Reductions based on new regulations (11,619) Balance—January 2, 2021 $ —
Summary of Valuation Allowance	2020 2019 Valuation Allowance: Beginning balance $ (1,675) $ (4,261) Loss carryforwards — — Current year decreases (increases) from operations — 2,586 Release of valuation allowance and other — — Ending balance $ (1,675) $ (1,675)

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Jan. 02, 2021
Earnings Per Share [Abstract]
Schedule of Basic Earnings Per Share	The following table shows the calculation of basic income per share: 2020 2019 2018 Net income attributable to Summit Inc. $ 137,967 $ 59,066 $ 33,906 Weighted average shares of Class A stock outstanding Add: Nonvested restricted stock awards of retirement eligible shares 212,443 — — Add: Weighted average shares of Class A stock outstanding 114,014,749 112,204,067 111,380,175 Weighted average basic shares outstanding 114,227,192 112,204,067 111,380,175 Basic earnings per share $ 1.21 $ 0.53 $ 0.30 Diluted net income attributable to Summit Inc. $ 137,967 $ 59,066 $ 33,906 Weighted average shares of Class A stock outstanding 114,014,749 112,204,067 111,380,175 Add: stock options 3,390 87,290 282,329 Add: warrants — 4,206 25,049 Add: restricted stock units 520,871 342,620 459,280 Add: performance stock units 92,758 46,535 169,813 Weighted average dilutive shares outstanding 114,631,768 112,684,718 112,316,646 Diluted earnings per share $ 1.20 $ 0.52 $ 0.30
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Excluded from the above calculations were the shares noted below as they were antidilutive: 2020 2019 2018 Antidilutive shares: LP Units 3,060,248 3,372,706 3,512,669 Warrants 100,037 — —

Stockholder's Equity_Members'_2

Stockholder's Equity/Members' Interest (Tables)	12 Months Ended
	Jan. 02, 2021
Company Information
Schedule of Changes in Ownership of Summit Holdings	The following table summarizes the changes in our ownership of Summit Holdings: Summit Inc. Shares (Class A) LP Units Total Summit Inc. Ownership Percentage Balance — December 29, 2018 111,658,927 3,435,518 115,094,445 97.0 % Exchanges during period 185,861 (185,861) — Stock option exercises 1,065,446 — 1,065,446 Other equity transactions 399,151 — 399,151 Balance — December 28, 2019 113,309,385 3,249,657 116,559,042 97.2 % Exchanges during period 376,487 (376,487) — Stock option exercises 54,517 — 54,517 Other equity transactions 650,206 — 650,206 Balance — January 2, 2021 114,390,595 2,873,170 117,263,765 97.5 %
Schedule of Changes in Each Component of Accumulated Other Comprehensive Income (Loss)	The changes in each component of accumulated other comprehensive income (loss) consisted of the following: Accumulated Foreign currency other Change in translation Cash flow hedge comprehensive retirement plans adjustments adjustments income (loss) Balance — December 29, 2018 $ 3,573 $ (2,147) $ 1,255 $ 2,681 Postretirement liability adjustment, net of tax (1,402) — — (1,402) Foreign currency translation adjustment, net of tax — 3,424 — 3,424 Income on cash flow hedges, net of tax — — (1,255) (1,255) Balance — December 28, 2019 $ 2,171 $ 1,277 $ — $ 3,448 Postretirement liability adjustment, net of tax (1,638) — — (1,638) Foreign currency translation adjustment, net of tax — 3,393 — 3,393 Balance — January 2, 2021 $ 533 $ 4,670 $ — $ 5,203
Summit Materials, LLC
Company Information
Schedule of Changes in Each Component of Accumulated Other Comprehensive Income (Loss)	The changes in each component of accumulated other comprehensive income (loss) consisted of the following: Accumulated Foreign currency other Change in translation Cash flow hedge comprehensive retirement plans adjustments adjustments income (loss) Balance — December 29, 2018 $ (4,392) $ (19,370) $ 146 $ (23,616) Postretirement liability adjustment (1,925) — — (1,925) Foreign currency translation adjustment — 4,716 — 4,716 Income on cash flow hedges — — (146) (146) Balance — December 28, 2019 $ (6,317) $ (14,654) $ — $ (20,971) Postretirement liability adjustment (2,229) — — (2,229) Foreign currency translation adjustment — 4,617 — 4,617 Balance — January 2, 2021 $ (8,546) $ (10,037) $ — $ (18,583)

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Jan. 02, 2021
Schedule Of Cash Flow Supplemental [Line Items]
Schedule of Supplemental Cash Flow Information	Supplemental cash flow information for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was as follows: 2020 2019 2018 Cash payments: Interest $ 99,551 $ 104,614 $ 103,250 Payments (refunds) for income taxes, net 1,754 (919) 3,340 Operating cash payments on operating leases 10,452 10,618 N/A Operating cash payments on finance leases 3,132 3,051 N/A Finance cash payments on finance leases 14,408 13,164 N/A Non cash financing activities: Right of use assets obtained in exchange for operating lease obligations $ 4,849 $ 5,842 N/A Right of use assets obtained in exchange for finance leases obligations 18,016 23,965 N/A Exchange of LP Units to shares of Class A common stock 8,227 3,847 7,499
Summit Materials, LLC
Schedule Of Cash Flow Supplemental [Line Items]
Schedule of Supplemental Cash Flow Information	Supplemental cash flow information for the years ended January 2, 2021, December 28, 2019 and December 29, 2018 was as follows: 2020 2019 2018 Cash payments: Interest $ 99,551 $ 104,614 $ 103,250 Payments (refunds) for income taxes, net 1,754 (919) 3,340 Operating cash payments on operating leases 10,452 10,618 N/A Operating cash payments on finance leases 3,132 3,051 N/A Finance cash payments on finance leases 14,408 13,164 N/A Non cash financing activities: Right of use assets obtained in exchange for operating lease obligations $ 4,849 $ 5,842 N/A Right of use assets obtained in exchange for finance leases obligations 18,016 23,965 N/A

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Jan. 02, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Information for the Equity Awards Granted	The following table summarizes information for the equity awards granted in 2020: Options Restricted Stock Units Performance Stock Units Warrants Weighted Weighted Weighted Weighted average grant- Number of average grant- Number of average grant- average grant- Number of date fair value restricted date fair value performance date fair value Number of date fair value options per unit stock units per unit stock units per unit warrants per unit Beginning balance—December 28, 2019 2,128,107 $ 9.08 1,556,636 $ 20.29 390,645 $ 31.08 100,037 $ 18.00 Granted — — 1,379,943 18.10 199,946 23.43 — — Forfeited/ Canceled (35,117) 12.30 (154,283) 19.12 (112,416) 26.54 — — Exercised (54,517) 10.10 — — — — — — Vested — — (647,345) 21.28 (49,300) 32 — — Balance—January 2, 2021 2,038,473 $ 9.16 2,134,951 $ 18.64 428,875 $ 28.64 100,037 $ 18.00
Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Information for the Equity Awards Granted	The following table summarizes information for the equity awards granted in 2020: Options Restricted Stock Units Performance Stock Units Warrants Weighted Weighted Weighted Weighted average grant- Number of average grant- Number of average grant- average grant- Number of date fair value restricted date fair value performance date fair value Number of date fair value options per unit stock units per unit stock units per unit warrants per unit Beginning balance—December 28, 2019 2,128,107 $ 9.08 1,556,636 $ 20.29 390,645 $ 31.08 100,037 $ 18.00 Granted — — 1,379,943 18.10 199,946 23.43 — — Forfeited/ Canceled (35,117) 12.30 (154,283) 19.12 (112,416) 26.54 — — Exercised (54,517) 10.10 — — — — — — Vested — — (647,345) 21.28 (49,300) 32 — — Balance—January 2, 2021 2,038,473 $ 9.16 2,134,951 $ 18.64 428,875 $ 28.64 100,037 $ 18.00

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Jan. 02, 2021
Defined Benefit Plan Disclosure [Line Items]
Obligations and Funded Status	The following information is as of January 2, 2021 and December 28, 2019 and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. Change in benefit obligations: Beginning of period $ 26,181 $ 9,090 $ 24,203 $ 9,203 Service cost 71 176 60 166 Interest cost 733 242 928 321 Actuarial (gain) loss 2,425 676 2,571 165 Benefits paid (1,583) (955) (1,581) (765) End of period $ 27,827 $ 9,229 $ 26,181 $ 9,090 Change in fair value of plan assets: Beginning of period $ 18,242 $ — $ 17,449 $ — Actual return on plan assets 1,916 — 2,055 — Employer contributions 483 955 319 765 Benefits paid (1,583) (955) (1,581) (765) End of period $ 19,058 $ — $ 18,242 $ — Funded status of plans $ (8,769) $ (9,229) $ (7,939) $ (9,090) Current liabilities $ — $ (636) $ — $ (653) Noncurrent liabilities (8,769) (8,593) (7,939) (8,437) Liability recognized $ (8,769) $ (9,229) $ (7,939) $ (9,090) Amounts recognized in accumulated other comprehensive income: Net actuarial (gain) loss $ 10,689 $ 2,707 $ 9,286 $ 2,121 Prior service cost — (1,690) — (1,931) Total amount recognized $ 10,689 $ 1,017 $ 9,286 $ 190
Amounts Recognized in Other Comprehensive (Gain) Loss	The amount recognized in accumulated other comprehensive income (“AOCI”) is the actuarial loss (credit) and prior service cost, which has not yet been recognized in periodic benefit cost. 2020 2019 2018 Pension Healthcare Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. benefits & Life Ins. Amounts recognized in other comprehensive (income) loss: Net actuarial loss (gain) $ 1,728 $ 675 $ 1,760 $ 165 $ (1,300) $ (172) Amortization of prior year service cost — 241 — 241 — 241 Amortization of gain (326) (89) (202) (39) (312) (118) Total amount recognized $ 1,402 $ 827 $ 1,558 $ 367 $ (1,612) $ (49)
Schedule of Net Benefit Costs	Components of net periodic benefit cost: Service cost $ 71 $ 176 $ 60 $ 166 $ 67 $ 170 Interest cost 733 242 928 321 898 317 Amortization of gain 326 89 202 39 312 118 Expected return on plan assets (1,221) — (1,244) — (1,284) — Amortization of prior service credit — (241) — (241) — (241) Net periodic (expense) benefit cost $ (91) $ 266 $ (54) $ 285 $ (7) $ 364
Schedule of Assumptions Used	Weighted-average assumptions used to determine the benefit obligations as of year-end 2020 and 2019 are: 2020 2019 Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 1.84% - 2.14% 1.80% - 1.82% 2.78% - 2.96% 2.73% - 2.79% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A Weighted-average assumptions used to determine net periodic benefit cost for years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Healthcare Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 2.78% - 2.96% 2.73% - 2.79% 3.90% - 4.02% 3.87% - 3.91% 3.23% - 3.37% 3.20% - 3.25% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A 7.00% N/A
Fair Value of Company's Pension Plans' Assets	The fair value of the Plans’ assets by asset class and fair value hierarchy level as of January 2, 2021 and December 28, 2019 are as follows: 2020 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 3,294 $ 3,294 $ — Intermediate—corporate 3,218 — 3,218 Short-term—government 705 705 — Short-term—corporate 448 — 448 International 1,086 — 1,086 Equity securities: U.S. Large cap value 1,516 1,516 — U.S. Large cap growth 1,483 1,483 — U.S. Mid cap value 631 631 — U.S. Mid cap growth 619 619 — U.S. Small cap value 663 663 — U.S. Small cap growth 650 650 — International 1,227 407 820 Emerging Markets 409 409 — Commodities Broad Basket 1,002 182 820 Cash 2,107 2,107 — Total $ 19,058 $ 12,666 $ 6,392 2019 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 2,482 $ 2,482 $ — Intermediate—corporate 1,066 — 1,066 Short-term—government 1,387 1,387 — Short-term—corporate 3,173 — 3,173 International 1,387 — 1,387 Equity securities: U.S. Large cap value 1,225 1,225 — U.S. Large cap growth 1,167 1,167 — U.S. Mid cap value 581 581 — U.S. Mid cap growth 578 578 — U.S. Small cap value 583 583 — U.S. Small cap growth 593 593 — Managed Futures 340 — 340 International 1,174 386 788 Emerging Markets 394 394 — Commodities Broad Basket 1,118 362 756 Cash 994 994 — Total $ 18,242 $ 10,732 $ 7,510
Estimated Benefit Payments	The estimated benefit payments for each of the next five years and the five-year period thereafter are as follows: Pension Healthcare and Life benefits Insurance Benefits 2021 $ 1,692 $ 636 2022 1,693 630 2023 1,696 617 2024 1,655 619 2025 1,613 627 2026 - 2030 7,597 3,139
Schedule of Multiemployer Plans	Expiration Date of Pension Protection Act FIP/RP Status Contributions of Company Collective- Pension EIN/ Pension Zone Status Pending/ ($ in thousands) Surcharge Bargaining Trust Fund Plan Number 2020 2019 Implemented 2020 2019 Imposed Agreement Construction Industry Laborers Pension Fund 43-6060737/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None $ 100 $ 112 No 3/31/2021 Operating Engineers Local 101 Pension Plan 43-6059213/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None 20 23 No 3/31/2021 Total Contributions $ 120 $ 135
Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Obligations and Funded Status	The following information is as of January 2, 2021 and December 28, 2019 and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. Change in benefit obligations: Beginning of period $ 26,181 $ 9,090 $ 24,203 $ 9,203 Service cost 71 176 60 166 Interest cost 733 242 928 321 Actuarial (gain) loss 2,425 676 2,571 165 Benefits paid (1,583) (955) (1,581) (765) End of period $ 27,827 $ 9,229 $ 26,181 $ 9,090 Change in fair value of plan assets: Beginning of period $ 18,242 $ — $ 17,449 $ — Actual return on plan assets 1,916 — 2,055 — Employer contributions 483 955 319 765 Benefits paid (1,583) (955) (1,581) (765) End of period $ 19,058 $ — $ 18,242 $ — Funded status of plans $ (8,769) $ (9,229) $ (7,939) $ (9,090) Current liabilities $ — $ (636) $ — $ (653) Noncurrent liabilities (8,769) (8,593) (7,939) (8,437) Liability recognized $ (8,769) $ (9,229) $ (7,939) $ (9,090) Amounts recognized in accumulated other comprehensive income: Net actuarial (gain) loss $ 10,689 $ 2,707 $ 9,286 $ 2,121 Prior service cost — (1,690) — (1,931) Total amount recognized $ 10,689 $ 1,017 $ 9,286 $ 190
Amounts Recognized in Other Comprehensive (Gain) Loss	2020 2019 2018 Pension Healthcare Pension Healthcare Pension Healthcare benefits & Life Ins. benefits & Life Ins. benefits & Life Ins. Amounts recognized in other comprehensive (income) loss: Net actuarial loss (gain) $ 1,728 $ 675 $ 1,760 $ 165 $ (1,300) $ (172) Amortization of prior year service cost — 241 — 241 — 241 Amortization of gain (326) (89) (202) (39) (312) (118) Total amount recognized $ 1,402 $ 827 $ 1,558 $ 367 $ (1,612) $ (49) Components of net periodic benefit cost: Service cost $ 71 $ 176 $ 60 $ 166 $ 67 $ 170 Interest cost 733 242 928 321 898 317 Amortization of gain 326 89 202 39 312 118 Expected return on plan assets (1,221) — (1,244) — (1,284) — Amortization of prior service credit — (241) — (241) — (241) Net periodic (expense) benefit cost $ (91) $ 266 $ (54) $ 285 $ (7) $ 364
Schedule of Assumptions Used	Weighted-average assumptions used to determine the benefit obligations as of year-end 2020 and 2019 are: 2020 2019 Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 1.84% - 2.14% 1.80% - 1.82% 2.78% - 2.96% 2.73% - 2.79% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A Weighted-average assumptions used to determine net periodic benefit cost for years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Healthcare Healthcare Healthcare Pension benefits & Life Ins. Pension benefits & Life Ins. Pension benefits & Life Ins. Discount rate 2.78% - 2.96% 2.73% - 2.79% 3.90% - 4.02% 3.87% - 3.91% 3.23% - 3.37% 3.20% - 3.25% Expected long-term rate of return on plan assets 7.00% N/A 7.00% N/A 7.00% N/A
Fair Value of Company's Pension Plans' Assets	The fair value of the Plans’ assets by asset class and fair value hierarchy level as of January 2, 2021 and December 28, 2019 are as follows: 2020 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 3,294 $ 3,294 $ — Intermediate—corporate 3,218 — 3,218 Short-term—government 705 705 — Short-term—corporate 448 — 448 International 1,086 — 1,086 Equity securities: U.S. Large cap value 1,516 1,516 — U.S. Large cap growth 1,483 1,483 — U.S. Mid cap value 631 631 — U.S. Mid cap growth 619 619 — U.S. Small cap value 663 663 — U.S. Small cap growth 650 650 — International 1,227 407 820 Emerging Markets 409 409 — Commodities Broad Basket 1,002 182 820 Cash 2,107 2,107 — Total $ 19,058 $ 12,666 $ 6,392 2019 Quoted prices in active Total fair markets for identical Observable value assets (Level 1) inputs (Level 2) Fixed income securities: Intermediate—government $ 2,482 $ 2,482 $ — Intermediate—corporate 1,066 — 1,066 Short-term—government 1,387 1,387 — Short-term—corporate 3,173 — 3,173 International 1,387 — 1,387 Equity securities: U.S. Large cap value 1,225 1,225 — U.S. Large cap growth 1,167 1,167 — U.S. Mid cap value 581 581 — U.S. Mid cap growth 578 578 — U.S. Small cap value 583 583 — U.S. Small cap growth 593 593 — Managed Futures 340 — 340 International 1,174 386 788 Emerging Markets 394 394 — Commodities Broad Basket 1,118 362 756 Cash 994 994 — Total $ 18,242 $ 10,732 $ 7,510
Estimated Benefit Payments	The estimated benefit payments for each of the next five years and the five-year period thereafter are as follows: Pension Healthcare and Life benefits Insurance Benefits 2021 $ 1,692 $ 636 2022 1,693 630 2023 1,696 617 2024 1,655 619 2025 1,613 627 2026 - 2030 7,597 3,139
Schedule of Multiemployer Plans	Expiration Date of Pension Protection Act FIP/RP Status Contributions of Company Collective- Pension EIN/ Pension Zone Status Pending/ ($ in thousands) Surcharge Bargaining Trust Fund Plan Number 2020 2019 Implemented 2020 2019 Imposed Agreement Construction Industry Laborers Pension Fund 43-6060737/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None $ 100 $ 112 No 3/31/2021 Operating Engineers Local 101 Pension Plan 43-6059213/001 Green - as of December 31, 2019 Green - as of December 31, 2018 None 20 23 No 3/31/2021 Total Contributions $ 120 $ 135

Accrued Mining and Landfill R_2

Accrued Mining and Landfill Reclamation (Tables)	12 Months Ended
	Jan. 02, 2021
Asset Retirement Obligations [Line Items]
Activity for Asset Retirement Obligations	The following table presents the activity for the asset retirement obligations for the years ended January 2, 2021 and December 28, 2019: 2020 2019 Beginning balance $ 36,676 $ 30,999 Acquired obligations 861 805 Change in cost estimate 6,523 4,468 Settlement of reclamation obligations (3,095) (1,812) Accretion expense 2,638 2,216 Ending balance $ 43,603 $ 36,676
Summit Materials, LLC
Asset Retirement Obligations [Line Items]
Activity for Asset Retirement Obligations	The following table presents the activity for the asset retirement obligations for the years ended January 2, 2021 and December 28, 2019: 2020 2019 Beginning balance $ 36,676 $ 30,999 Acquired obligations 861 805 Change in cost estimate 6,523 4,468 Settlement of reclamation obligations (3,095) (1,812) Accretion expense 2,638 2,216 Ending balance $ 43,603 $ 36,676

Leases (Tables)

Leases (Tables)	12 Months Ended
	Jan. 02, 2021
Lessee, Lease, Description [Line Items]
Schedule of Lease Cost	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Lease Assets and Liabilities	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Finance Lease Liability Maturities	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Operating Lease Liability Maturities	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Contractual Commitments for Royalty Agreements	Minimum contractual commitments for the subsequent five years under royalty agreements are as follows: Royalty Agreements 2021 $ 9,916 2022 9,880 2023 9,594 2024 9,295 2025 9,052
Summit Materials, LLC
Lessee, Lease, Description [Line Items]
Schedule of Lease Cost	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Lease Assets and Liabilities	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Finance Lease Liability Maturities	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Operating Lease Liability Maturities	The components of lease expense were as follows: 2020 2019 Operating lease cost $ 10,134 $ 10,451 Variable lease cost 316 423 Short-term lease cost 44,066 38,417 Financing lease cost: Amortization of right-of-use assets 12,598 11,062 Interest on lease liabilities 3,068 3,171 Total lease cost $ 70,182 $ 63,524 2020 2019 Supplemental balance sheet information related to leases: Operating leases: Operating lease right-of-use assets $ 28,543 $ 32,777 Current operating lease liabilities $ 8,188 $ 8,427 Noncurrent operating lease liabilities 21,500 25,381 Total operating lease liabilities $ 29,688 $ 33,808 Finance leases: Property and equipment, gross $ 92,679 $ 82,660 Less accumulated depreciation (32,828) (24,907) Property and equipment, net $ 59,851 $ 57,753 Current finance lease liabilities $ 24,601 $ 16,007 Long-term finance lease liabilities 31,727 40,410 Total finance lease liabilities $ 56,328 $ 56,417 2020 2019 Weighted average remaining lease term (years): Operating leases 8.7 8.6 Finance lease 2.4 2.6 Weighted average discount rate: Operating leases 5.3 % 5.5 % Finance lease 5.2 % 5.5 % Maturities of lease liabilities were as follows: Operating Leases Finance Leases 2021 $ 9,491 $ 26,742 2022 6,088 18,603 2023 4,663 7,053 2024 2,863 3,207 2025 1,781 2,573 Thereafter 12,961 2,831 Total lease payments 37,847 61,009 Less imputed interest (8,159) (4,681) Present value of lease payments $ 29,688 $ 56,328
Schedule of Contractual Commitments for Royalty Agreements	Minimum contractual commitments for the subsequent five years under royalty agreements are as follows: Royalty Agreements 2021 $ 9,916 2022 9,880 2023 9,594 2024 9,295 2025 9,052

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Jan. 02, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Schedule of Contingent Consideration and Derivatives Measured at Fair Value	The fair value of contingent consideration as of January 2, 2021 and December 28, 2019 was: 2020 2019 Current portion of acquisition-related liabilities and Accrued expenses: Contingent consideration $ 654 $ 1,967 Acquisition-related liabilities and Other noncurrent liabilities: Contingent consideration $ 1,209 $ 1,302
Schedule of Carrying Value and Fair Value of Financial Instruments	The carrying value and fair value of these financial instruments as of January 2, 2021 and December 28, 2019 were: January 2, 2021 December 28, 2019 Fair Value Carrying Value Fair Value Carrying Value Level 1 Long-term debt(1) $ 1,971,087 $ 1,915,425 $ 1,918,720 $ 1,872,273 Level 3 Current portion of deferred consideration and noncompete obligations(2) 9,611 9,611 30,733 30,733 Long term portion of deferred consideration and noncompete obligations(3) 11,037 11,037 18,499 18,499 _____________________ (1) $6.4 million and $7.9 million were included in current portion of debt as of January 2, 2021 and December 28, 2019, respectively. (2) Included in current portion of acquisition-related liabilities on the consolidated balance sheets. (3) Included in acquisition-related liabilities on the consolidated balance sheets.
Summit Materials, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Schedule of Contingent Consideration and Derivatives Measured at Fair Value	The fair value of contingent consideration as of January 2, 2021 and December 28, 2019 was: 2020 2019 Current portion of acquisition-related liabilities and Accrued expenses: Contingent consideration $ 654 $ 1,967 Acquisition-related liabilities and Other noncurrent liabilities: Contingent consideration $ 1,209 $ 1,302
Schedule of Carrying Value and Fair Value of Financial Instruments	The carrying value and fair value of these financial instruments as of January 2, 2021 and December 28, 2019 were: January 2, 2021 December 28, 2019 Fair Value Carrying Value Fair Value Carrying Value Level 1 Long-term debt(1) $ 1,971,087 $ 1,915,425 $ 1,918,720 $ 1,872,273 Level 3 Current portion of deferred consideration and noncompete obligations(2) 7,173 7,173 28,233 28,233 Long term portion of deferred consideration and noncompete obligations(3) 11,037 11,037 16,364 16,364 ______________________ (1) $6.4 million and $7.9 million were included in current portion of debt as of January 2, 2021 and December 28, 2019, respectively. (2) Included in current portion of acquisition-related liabilities on the consolidated balance sheets. (3) Included in acquisition-related liabilities on the consolidated balance sheets.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Jan. 02, 2021
Segment Reporting Information [Line Items]
Summary of Financial Data for Company's Reportable Business Segments	The following tables display selected financial data for the Company’s reportable business segments as of and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Revenue*: West $ 1,262,196 $ 1,122,338 $ 1,117,066 East 799,633 809,098 703,147 Cement 270,622 290,704 280,789 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ * Intercompany sales are immaterial and the presentation above only reflects sales to external customers. 2020 2019 2018 Income from operations before taxes $ 129,055 $ 78,224 $ 96,077 Interest expense 103,595 116,509 116,548 Depreciation, depletion and amortization 218,682 214,886 203,305 Accretion 2,638 2,216 1,605 Loss on debt financings 4,064 14,565 149 Tax receivable agreement (benefit) expense (7,559) 16,237 (22,684) Gain on sale of business — — (12,108) Transaction costs 2,747 2,222 4,238 Non-cash compensation 28,857 20,403 25,378 Other 2,957 (3,800) (6,247) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 Total Adjusted EBITDA by Segment: West $ 271,052 $ 204,964 $ 188,999 East 162,275 187,625 138,032 Cement 92,956 103,438 111,394 Corporate and other (41,247) (34,565) (32,164) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 2020 2019 2018 Purchases of property, plant and equipment West $ 67,500 $ 71,397 $ 120,657 East 92,528 77,894 64,384 Cement 15,071 25,691 28,036 Total reportable segments 175,099 174,982 213,077 Corporate and other 2,150 2,513 7,608 Total purchases of property, plant and equipment $ 177,249 $ 177,495 $ 220,685 2020 2019 2018 Depreciation, depletion, amortization and accretion: West $ 93,866 $ 93,256 $ 91,794 East 86,205 81,403 75,433 Cement 37,267 38,447 35,061 Total reportable segments 217,338 213,106 202,288 Corporate and other 3,982 3,996 2,622 Total depreciation, depletion, amortization and accretion $ 221,320 $ 217,102 $ 204,910 2020 2019 2018 Total assets: West $ 1,503,382 $ 1,379,684 $ 1,370,501 East 1,303,742 1,288,835 1,253,640 Cement 850,835 868,528 877,586 Total reportable segments 3,657,959 3,537,047 3,501,727 Corporate and other 650,052 530,509 355,914 Total $ 4,308,011 $ 4,067,556 $ 3,857,641
Summit Materials, LLC
Segment Reporting Information [Line Items]
Summary of Financial Data for Company's Reportable Business Segments	The following tables display selected financial data for the Company’s reportable business segments as of and for the years ended January 2, 2021, December 28, 2019 and December 29, 2018: 2020 2019 2018 Revenue*: West $ 1,262,196 $ 1,122,338 $ 1,117,066 East 799,633 809,098 703,147 Cement 270,622 290,704 280,789 Total revenue $ 2,332,451 $ 2,222,140 $ 2,101,002 ______________________ * Intercompany sales are immaterial and the presentation above only reflects sales to external customers. 2020 2019 2018 Income from operations before taxes $ 121,800 $ 94,982 $ 74,110 Interest expense 103,291 115,988 115,831 Depreciation, depletion and amortization 218,682 214,886 203,305 Accretion 2,638 2,216 1,605 Loss on debt financings 4,064 14,565 149 Gain on sale of business — — (12,108) Transaction costs 2,747 2,222 4,238 Non-cash compensation 28,857 20,403 25,378 Other 2,957 (3,800) (6,247) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 Total Adjusted EBITDA by Segment: West $ 271,052 $ 204,964 $ 188,999 East 162,275 187,625 138,032 Cement 92,956 103,438 111,394 Corporate and other (41,247) (34,565) (32,164) Total Adjusted EBITDA $ 485,036 $ 461,462 $ 406,261 2020 2019 2018 Purchases of property, plant and equipment West $ 67,500 $ 71,397 $ 120,657 East 92,528 77,894 64,384 Cement 15,071 25,691 28,036 Total reportable segments 175,099 174,982 213,077 Corporate and other 2,150 2,513 7,608 Total purchases of property, plant and equipment $ 177,249 $ 177,495 $ 220,685 2020 2019 2018 Depreciation, depletion, amortization and accretion: West $ 93,866 $ 93,256 $ 91,794 East 86,205 81,403 75,433 Cement 37,267 38,447 35,061 Total reportable segments 217,338 213,106 202,288 Corporate and other 3,982 3,996 2,622 Total depreciation, depletion, amortization and accretion $ 221,320 $ 217,102 $ 204,910 2020 2019 2018 Total assets: West $ 1,503,382 $ 1,379,684 $ 1,370,501 East 1,303,742 1,288,835 1,253,640 Cement 850,835 868,528 877,586 Total reportable segments 3,657,959 3,537,047 3,501,727 Corporate and other 419,175 319,176 131,517 Total $ 4,077,134 $ 3,856,223 $ 3,633,244

Senior Notes' Guarantor and N_2

Senior Notes' Guarantor and Non-Guarantor Financial Information (Tables) - Summit Materials, LLC	12 Months Ended
	Jan. 02, 2021
Condensed Financial Statements, Captions [Line Items]
Condensed Consolidating Balance Sheets	100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Assets Current assets: Cash and cash equivalents $ 401,074 $ 10,287 $ 10,461 $ (3,641) $ 418,181 Accounts receivable, net 4 230,199 24,384 109 254,696 Intercompany receivables 404,459 1,303,293 — (1,707,752) — Cost and estimated earnings in excess of billings — 7,504 1,162 — 8,666 Inventories — 193,417 6,891 — 200,308 Other current assets 2,840 6,797 1,791 — 11,428 Total current assets 808,377 1,751,497 44,689 (1,711,284) 893,279 Property, plant and equipment, net 9,410 1,746,045 94,714 — 1,850,169 Goodwill — 1,142,083 60,208 — 1,202,291 Intangible assets, net — 47,852 — — 47,852 Operating lease right-of-use assets 2,615 21,880 4,048 — 28,543 Other assets 4,022,729 207,699 493 (4,175,921) 55,000 Total assets $ 4,843,131 $ 4,917,056 $ 204,152 $ (5,887,205) $ 4,077,134 Liabilities and Member’s Interest Current liabilities: Current portion of debt $ 6,354 $ — $ — $ — $ 6,354 Current portion of acquisition-related liabilities — 7,827 — — 7,827 Accounts payable 3,889 108,805 8,619 109 121,422 Accrued expenses 54,108 106,320 4,014 (3,641) 160,801 Current operating lease liabilities 913 6,114 1,161 — 8,188 Intercompany payables 1,215,043 485,401 7,308 (1,707,752) — Billings in excess of costs and estimated earnings — 15,508 991 — 16,499 Total current liabilities 1,280,307 729,975 22,093 (1,711,284) 321,091 Long-term debt 1,892,347 — — — 1,892,347 Acquisition-related liabilities — 12,246 — — 12,246 Noncurrent operating lease liabilities 2,567 16,062 2,871 — 21,500 Other noncurrent liabilities 5,142 208,540 117,921 (164,421) 167,182 Total liabilities 3,180,363 966,823 142,885 (1,875,705) 2,414,366 Total member's interest 1,662,768 3,950,233 61,267 (4,011,500) 1,662,768 Total liabilities and member’s interest $ 4,843,131 $ 4,917,056 $ 204,152 $ (5,887,205) $ 4,077,134 Condensed Consolidating Balance Sheets December 28, 2019 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Assets Current assets: Cash and cash equivalents $ 302,474 $ 5,488 $ 9,834 $ (6,477) $ 311,319 Accounts receivable, net — 234,053 19,236 (33) 253,256 Intercompany receivables 443,323 942,385 — (1,385,708) — Cost and estimated earnings in excess of billings — 12,291 797 — 13,088 Inventories — 199,794 4,993 — 204,787 Other current assets 1,763 10,308 1,760 — 13,831 Total current assets 747,560 1,404,319 36,620 (1,392,218) 796,281 Property, plant and equipment, net 11,602 1,674,443 61,404 — 1,747,449 Goodwill — 1,142,063 58,636 — 1,200,699 Intangible assets, net — 23,498 — — 23,498 Operating lease right-of-use assets 3,316 24,551 4,910 — 32,777 Other assets 3,596,161 168,314 734 (3,709,690) 55,519 Total assets $ 4,358,639 $ 4,437,188 $ 162,304 $ (5,101,908) $ 3,856,223 Liabilities and Member’s Interest Current liabilities: Current portion of debt $ 7,942 $ — $ — $ — $ 7,942 Current portion of acquisition-related liabilities — 30,200 — — 30,200 Accounts payable 4,588 103,812 8,603 (33) 116,970 Accrued expenses 51,043 72,970 2,701 (6,477) 120,237 Current operating lease liabilities 764 6,571 1,092 — 8,427 Intercompany payables 922,356 447,827 15,525 (1,385,708) — Billings in excess of costs and estimated earnings — 12,183 1,681 — 13,864 Total current liabilities 986,693 673,563 29,602 (1,392,218) 297,640 Long-term debt 1,851,057 — — — 1,851,057 Acquisition-related liabilities — 17,666 — — 17,666 Noncurrent operating lease liabilities 3,480 18,047 3,854 — 25,381 Other noncurrent liabilities 4,259 203,919 80,169 (137,018) 151,329 Total liabilities 2,845,489 913,195 113,625 (1,529,236) 2,343,073 Total member's interest 1,513,150 3,523,993 48,679 (3,572,672) 1,513,150 Total liabilities and member’s interest $ 4,358,639 $ 4,437,188 $ 162,304 $ (5,101,908) $ 3,856,223
Condensed Consolidating Statements of Operations and Comprehensive Loss	100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Revenue $ — $ 2,259,865 $ 89,752 $ (17,166) $ 2,332,451 Cost of revenue (excluding items shown separately below) — 1,542,586 58,576 (17,166) 1,583,996 General and administrative expenses 72,504 217,897 11,561 — 301,962 Depreciation, depletion, amortization and accretion 3,983 210,038 7,299 — 221,320 Operating (loss) income (76,487) 289,344 12,316 — 225,173 Other (income) loss, net (328,914) (2,473) (198) 331,667 82 Interest expense (income) 130,176 (31,402) 4,517 — 103,291 Income from operation before taxes 122,251 323,219 7,997 (331,667) 121,800 Income tax expense (benefit) 1,514 (4,737) 4,286 — 1,063 Net income attributable to Summit LLC $ 120,737 $ 327,956 $ 3,711 $ (331,667) $ 120,737 Comprehensive income (loss) attributable to member of Summit Materials, LLC $ 123,125 $ 330,185 $ (906) $ (329,279) $ 123,125 Condensed Consolidating Statements of Operations and Comprehensive Income Year ended December 28, 2019 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Revenue $ — $ 2,139,457 $ 94,879 $ (12,196) $ 2,222,140 Cost of revenue (excluding items shown separately below) — 1,473,124 65,404 (12,196) 1,526,332 General and administrative expenses 58,099 195,683 11,366 — 265,148 Depreciation, depletion, amortization and accretion 3,997 207,277 5,828 — 217,102 Operating (loss) income (62,096) 263,373 12,281 — 213,558 Other (income) loss, net (279,517) (8,767) (790) 291,662 2,588 Interest expense (income) 127,734 (16,561) 4,815 — 115,988 Income from operation before taxes 89,687 288,701 8,256 (291,662) 94,982 Income tax expense 1,090 3,377 1,918 — 6,385 Net income attributable to Summit LLC $ 88,597 $ 285,324 $ 6,338 $ (291,662) $ 88,597 Comprehensive income attributable to member of Summit Materials, LLC $ 91,242 $ 287,395 $ 1,622 $ (289,017) $ 91,242 Condensed Consolidating Statements of Operations and Comprehensive Income Year ended December 29, 2018 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Revenue $ — $ 2,018,428 $ 88,658 $ (6,084) $ 2,101,002 Cost of revenue (excluding items shown separately below) — 1,416,222 65,641 (6,084) 1,475,779 General and administrative expenses 62,376 184,917 10,554 — 257,847 Depreciation, depletion, amortization and accretion 2,622 197,406 4,882 — 204,910 Operating (loss) income (64,998) 219,883 7,581 — 162,466 Other (income) loss, net (249,204) (14,643) 823 247,657 (15,367) Interest expense 118,857 (7,818) 4,792 — 115,831 Gain on sale of business — (12,108) — — (12,108) Income from continuing operations before taxes 65,349 254,452 1,966 (247,657) 74,110 Income tax (benefit) expense 1,512 8,226 535 — 10,273 Net income attributable to member of Summit Materials, LLC $ 63,837 $ 246,226 $ 1,431 $ (247,657) $ 63,837 Comprehensive income attributable to member of Summit Materials, LLC $ 57,356 $ 243,359 $ 10,779 $ (254,138) $ 57,356
Condensed Consolidating Statements of Cash Flows	100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Net cash (used in) provided by operating activities $ (135,895) $ 502,595 $ 42,169 $ — $ 408,869 Cash flow from investing activities: Acquisitions, net of cash acquired — (92,085) (31,392) — (123,477) Purchase of property, plant and equipment (2,150) (173,228) (1,871) — (177,249) Proceeds from the sale of property, plant, and equipment — 13,935 83 — 14,018 Other — 1,121 — — 1,121 Net cash used for investing activities (2,150) (250,257) (33,180) — (285,587) Cash flow from financing activities: Proceeds from investment by member (91,142) 87,925 4,260 — 1,043 Net proceeds from debt issuance 700,000 — — — 700,000 Loans received from and payments made on loans from other Summit Companies 298,656 (288,711) (12,781) 2,836 — Payments on long-term debt (657,942) (15,911) (192) — (674,045) Payments on acquisition-related liabilities — (30,757) — — (30,757) Debt issuance costs (9,605) — — — (9,605) Distributions from partnership (2,500) — — — (2,500) Other (822) (85) — — (907) Net cash provided by (used in) financing activities 236,645 (247,539) (8,713) 2,836 (16,771) Impact of cash on foreign currency — — 351 — 351 Net increase in cash 98,600 4,799 627 2,836 106,862 Cash — Beginning of period 302,474 5,488 9,834 (6,477) 311,319 Cash — End of period $ 401,074 $ 10,287 $ 10,461 $ (3,641) $ 418,181 Condensed Consolidating Statements of Cash Flows For the year ended December 28, 2019 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Net cash (used in) provided by operating activities $ (112,019) $ 431,323 $ 17,880 $ — $ 337,184 Cash flow from investing activities: Acquisitions, net of cash acquired — (5,392) — — (5,392) Purchase of property, plant and equipment (2,513) (163,652) (11,330) — (177,495) Proceeds from the sale of property, plant, and equipment — 21,083 90 — 21,173 Proceeds from the sale of a business — 21,564 — — 21,564 Other — (1,095) — — (1,095) Net cash used for investing activities (2,513) (149,056) (11,240) — (162,809) Cash flow from financing activities: Proceeds from investment by member (21,614) 40,690 — — 19,076 Net proceeds from debt issuance 300,000 — — — 300,000 Loans received from and payments made on loans from other Summit Companies 287,029 (280,836) (4,586) (1,607) — Payments on long-term debt (256,354) (13,650) (225) — (270,229) Payments on acquisition-related liabilities — (31,383) — — (31,383) Financing costs (6,312) — — — (6,312) Distributions from partnership (2,500) — — — (2,500) Other (462) (40) — — (502) Net cash provided by (used in) financing activities 299,787 (285,219) (4,811) (1,607) 8,150 Impact of cash on foreign currency — — 286 — 286 Net increase (decrease) in cash 185,255 (2,952) 2,115 (1,607) 182,811 Cash — Beginning of period 117,219 8,440 7,719 (4,870) 128,508 Cash — End of period $ 302,474 $ 5,488 $ 9,834 $ (6,477) $ 311,319 Condensed Consolidating Statements of Cash Flows For the year ended December 29, 2018 100% Owned Non- Issuers Guarantors Guarantors Eliminations Consolidated Net cash (used in) provided by operating activities $ (142,315) $ 340,401 $ 11,282 $ — $ 209,368 Cash flow from investing activities: Acquisitions, net of cash acquired — (246,017) — — (246,017) Purchase of property, plant and equipment (7,607) (188,435) (24,643) — (220,685) Proceeds from the sale of property, plant, and equipment — 21,263 372 — 21,635 Proceeds from the sale of a business — 21,564 — — 21,564 Other — 3,804 — — 3,804 Net cash used for investing activities (7,607) (387,821) (24,271) — (419,699) Cash flow from financing activities: Proceeds from investment by member (146,533) 162,148 — — 15,615 Net proceeds from debt issuance 64,500 — — — 64,500 Loans received from and payments made on loans from other Summit Companies 51,696 (65,845) 6,647 7,502 — Payments on long-term debt (69,265) (15,662) (115) — (85,042) Payments on acquisition-related liabilities — (34,004) — — (34,004) Financing costs (550) — — — (550) Distributions from partnership (2,569) — — — (2,569) Other (879) (1,031) (33) — (1,943) Net cash provided by financing activities (103,600) 45,606 6,499 7,502 (43,993) Impact of cash on foreign currency — — (724) — (724) Net (decrease) increase in cash (253,522) (1,814) (7,214) 7,502 (255,048) Cash — Beginning of period 370,741 10,254 14,933 (12,372) 383,556 Cash — End of period $ 117,219 $ 8,440 $ 7,719 $ (4,870) $ 128,508

Summary of Organization and S_3

Summary of Organization and Significant Accounting Policies - General Information and Equity Offerings (Details)	12 Months Ended
	Jan. 02, 2021statesegmentplant	Dec. 28, 2019
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Number of operating segments	3
Number of reportable segments	3
Number of states in which the entity operates | state	23
Summit Materials, LLC
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Number of operating segments	3
Number of reportable segments	3
Number of states in which the entity operates | state	23
Summit Materials, LLC | Ohio Valley Asphalt
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Noncontrolling interest elimination (as a percent)	20.00%
Summit Materials, LLC | Continental Cement
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Noncontrolling interest elimination (as a percent)	30.00%
Summit Holdings LP
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Voting power (as a percent)		100.00%
Cement Plant
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Number of plants | plant	2
Cement Plant | Summit Materials, LLC
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Number of plants | plant	2
Tax Receivable Agreement | Summit Holdings LP
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Percentage of benefits to be paid on tax receivable agreement	85.00%
Minimum | Product
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Collection terms	30 days
Minimum | Product | Summit Materials, LLC
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Collection terms	30 days
Maximum | Product
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Collection terms	60 days
Maximum | Product | Summit Materials, LLC
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Collection terms	60 days
Maximum | Service
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Collection terms	90 days
Maximum | Service | Summit Materials, LLC
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements
Collection terms	90 days

Summary of Organization and S_4

Summary of Organization and Significant Accounting Policies - Prior Year Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Reclassification [Line Items]
Transaction costs	$ 2,747	$ 2,222	$ 4,238
Gain on sale of property, plant and equipment	7,569	10,665	12,555
Summit Materials, LLC
Reclassification [Line Items]
Transaction costs	2,747	2,222	4,238
Gain on sale of property, plant and equipment	$ 7,569	10,665	12,555
Reclass From Separate Line Item To General And Administrative Expenses
Reclassification [Line Items]
Transaction costs		2,200	4,200
Reclass From Separate Line Item To General And Administrative Expenses | Summit Materials, LLC
Reclassification [Line Items]
Transaction costs		2,200	4,200
Reclass From General And Administrative Expenses To Separate Line Item
Reclassification [Line Items]
Gain on sale of property, plant and equipment		10,700	12,600
Reclass From General And Administrative Expenses To Separate Line Item | Summit Materials, LLC
Reclassification [Line Items]
Gain on sale of property, plant and equipment		$ 10,700	$ 12,600

Summary of Organization and S_5

Summary of Organization and Significant Accounting Policies - New Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019	Dec. 30, 2018
New Accounting Standards
Operating lease right-of-use assets	$ 28,543	$ 32,777
Operating lease liability	29,688	33,808
Accounting Standards Update 2016-02
New Accounting Standards
Operating lease right-of-use assets			$ 36,800
Operating lease liability			36,800
Summit Materials, LLC
New Accounting Standards
Operating lease right-of-use assets	28,543	32,777
Operating lease liability	$ 29,688	$ 33,808
Summit Materials, LLC | Accounting Standards Update 2016-02
New Accounting Standards
Operating lease right-of-use assets			36,800
Operating lease liability			$ 36,800

Acquisitions - Acquisitions by

Acquisitions - Acquisitions by Region (Details) - acquistiion	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
West
Business Acquisition [Line Items]
Number of business acquisitions	2	2	5
East
Business Acquisition [Line Items]
Number of business acquisitions	1	0	7
Summit Materials, LLC | West
Business Acquisition [Line Items]
Number of business acquisitions	2	2	5
Summit Materials, LLC | East
Business Acquisition [Line Items]
Number of business acquisitions	1	0	7

Acquisitions - Summary of Asset

Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,201,291	$ 1,199,699	$ 1,192,028
Summit Materials, LLC
Business Acquisition [Line Items]
Goodwill	1,202,291	1,200,699	$ 1,193,028
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Financial assets	8,696	0
Inventories	2,856	52
Property, plant and equipment	130,042	3,542
Other assets	2,790	0
Financial liabilities	(4,469)	(36)
Other long-term liabilities	(16,069)	0
Net assets acquired	123,846	3,558
Goodwill	0	1,834
Purchase price	123,846	5,392
Other	(369)	0
Net cash paid for acquisitions	123,477	5,392
Series of Individually Immaterial Business Acquisitions | Summit Materials, LLC
Business Acquisition [Line Items]
Financial assets	8,696	0
Inventories	2,856	52
Property, plant and equipment	130,042	3,542
Other assets	2,790	0
Financial liabilities	(4,469)	(36)
Other long-term liabilities	(16,069)	0
Net assets acquired	123,846	3,558
Goodwill	0	1,834
Purchase price	123,846	5,392
Other	(369)	0
Net cash paid for acquisitions	$ 123,477	$ 5,392

Acquisitions - Contractual Obli

Acquisitions - Contractual Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Remaining payments on contractual obligations
Noncompete agreements, payment term (in general)	5 years
Minimum
Remaining payments on contractual obligations
Term of payment for deferred consideration		5 years
Maximum
Remaining payments on contractual obligations
Term of payment for deferred consideration		20 years
Noncompete and Deferred Consideration Agreements
Remaining payments on contractual obligations
2021	$ 9,705
2022	3,411
2023	2,657
2024	2,620
2025	2,567
Thereafter	4,454
Total scheduled payments	25,414
Present value adjustments	(4,766)
Total noncompete obligations and deferred consideration	$ 20,648
Summit Materials, LLC
Remaining payments on contractual obligations
Noncompete agreements, payment term (in general)	5 years
Summit Materials, LLC | Minimum
Remaining payments on contractual obligations
Term of payment for deferred consideration	5 years
Summit Materials, LLC | Maximum
Remaining payments on contractual obligations
Term of payment for deferred consideration	20 years
Summit Materials, LLC | Noncompete and Deferred Consideration Agreements
Remaining payments on contractual obligations
2021	$ 7,205
2022	3,411
2023	2,657
2024	2,620
2025	2,567
Thereafter	4,454
Total scheduled payments	22,914
Present value adjustments	(4,704)
Total noncompete obligations and deferred consideration	$ 18,210

Goodwill - Narrative (Details)

Goodwill - Narrative (Details)	3 Months Ended	12 Months Ended
	Jan. 02, 2021reportingUnit	Jan. 02, 2021USD ($)reportingUnit	Dec. 29, 2018USD ($)
Goodwill
Number of reporting units with goodwill | reportingUnit		11
Number of reporting units more likely than not fair value exceeds carrying value | reportingUnit	7
Goodwill, impairment loss | $		$ 0
Accumulated impairment losses | $			$ 68,200,000
Summit Materials, LLC
Goodwill
Number of reporting units with goodwill | reportingUnit		11
Number of reporting units more likely than not fair value exceeds carrying value | reportingUnit	7
Goodwill, impairment loss | $		$ 0
Accumulated impairment losses | $			$ 68,200,000

Goodwill - Summary of Goodwill

Goodwill - Summary of Goodwill by Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Goodwill [Roll Forward]
Beginning balance	$ 1,199,699	$ 1,192,028
Acquisitions	19	5,278
Foreign currency translation adjustments	1,573	2,393
Ending balance	1,201,291	1,199,699
Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	1,200,699	1,193,028
Acquisitions	19	5,278
Foreign currency translation adjustments	1,573	2,393
Ending balance	1,202,291	1,200,699
West
Goodwill [Roll Forward]
Beginning balance	584,617	580,567
Acquisitions	19	1,657
Foreign currency translation adjustments	1,573	2,393
Ending balance	586,209	584,617
West | Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	585,617	581,567
Acquisitions	19	1,657
Foreign currency translation adjustments	1,573	2,393
Ending balance	587,209	585,617
East
Goodwill [Roll Forward]
Beginning balance	410,426	406,805
Acquisitions	0	3,621
Foreign currency translation adjustments	0	0
Ending balance	410,426	410,426
East | Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	410,426	406,805
Acquisitions	0	3,621
Foreign currency translation adjustments	0	0
Ending balance	410,426	410,426
Cement
Goodwill [Roll Forward]
Beginning balance	204,656	204,656
Acquisitions	0	0
Foreign currency translation adjustments	0	0
Ending balance	204,656	204,656
Cement | Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	204,656	204,656
Acquisitions	0	0
Foreign currency translation adjustments	0	0
Ending balance	$ 204,656	$ 204,656

Revenue Recognition - By Produc

Revenue Recognition - By Product (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Revenue from External Customer [Line Items]
Revenue	$ 2,332,451	$ 2,222,140	$ 2,101,002
Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	2,332,451	2,222,140	2,101,002
Aggregates
Revenue from External Customer [Line Items]
Revenue	498,007	469,670	373,824
Aggregates | Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	498,007	469,670	373,824
Cement
Revenue from External Customer [Line Items]
Revenue	257,629	266,235	258,876
Cement | Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	257,629	266,235	258,876
Ready-mix concrete
Revenue from External Customer [Line Items]
Revenue	668,060	607,622	584,114
Ready-mix concrete | Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	668,060	607,622	584,114
Asphalt
Revenue from External Customer [Line Items]
Revenue	349,350	330,750	301,247
Asphalt | Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	349,350	330,750	301,247
Paving and related services
Revenue from External Customer [Line Items]
Revenue	381,430	360,234	379,540
Paving and related services | Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	381,430	360,234	379,540
Other
Revenue from External Customer [Line Items]
Revenue	177,975	187,629	203,401
Other | Summit Materials, LLC
Revenue from External Customer [Line Items]
Revenue	$ 177,975	$ 187,629	$ 203,401

Revenue Recognition - Contract

Revenue Recognition - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Change in Contract with Customer, Asset [Abstract]
Balance—December 28, 2019	$ 13,088
Changes in revenue billed, contract price or cost estimates	(4,535)	$ (5,558)	$ 8,702
Other	113
Balance—January 2, 2021	8,666	13,088
Change in Contract with Customer, Liability [Abstract]
Balance—December 28, 2019	13,864
Changes in revenue billed, contract price or cost estimates	2,616	1,988	(5,052)
Other	19
Balance—January 2, 2021	16,499	13,864
Summit Materials, LLC
Change in Contract with Customer, Asset [Abstract]
Balance—December 28, 2019	13,088
Changes in revenue billed, contract price or cost estimates	(4,535)	(5,558)	8,702
Other	113
Balance—January 2, 2021	8,666	13,088
Change in Contract with Customer, Liability [Abstract]
Balance—December 28, 2019	13,864
Changes in revenue billed, contract price or cost estimates	2,616	1,988	$ (5,052)
Other	19
Balance—January 2, 2021	$ 16,499	$ 13,864

Revenue Recognition - Summary o

Revenue Recognition - Summary of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable	$ 191,871	$ 191,672
Construction contract receivables	47,179	47,966
Retention receivables	18,824	17,808
Receivables from related parties	1,339	1,596
Accounts receivable	259,213	259,042
Less: Allowance for doubtful accounts	(4,517)	(5,786)
Accounts receivable, net	254,696	253,256
Summit Materials, LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable	191,871	191,672
Construction contract receivables	47,179	47,966
Retention receivables	18,824	17,808
Receivables from related parties	1,339	1,596
Accounts receivable	259,213	259,042
Less: Allowance for doubtful accounts	(4,517)	(5,786)
Accounts receivable, net	$ 254,696	$ 253,256
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
General collection and billing period for retention receivables	1 year
Maximum | Summit Materials, LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
General collection and billing period for retention receivables	1 year

Inventories - Components of Inv

Inventories - Components of Inventories (Details) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Inventory [Line Items]
Aggregate stockpiles	$ 137,938	$ 140,461
Finished goods	32,993	33,023
Work in process	9,281	7,664
Raw materials	20,096	23,639
Total	200,308	204,787
Summit Materials, LLC
Inventory [Line Items]
Aggregate stockpiles	137,938	140,461
Finished goods	32,993	33,023
Work in process	9,281	7,664
Raw materials	20,096	23,639
Total	$ 200,308	$ 204,787

Property, Plant and Equipment_3

Property, Plant and Equipment, net and Intangibles, net - Components of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 2,983,094	$ 2,703,264
Less accumulated depreciation, depletion and amortization	(1,132,925)	(955,815)
Property, plant and equipment including finance lease right-of-use asset, net	1,850,169	1,747,449
Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	2,983,094	2,703,264
Less accumulated depreciation, depletion and amortization	(1,132,925)	(955,815)
Property, plant and equipment including finance lease right-of-use asset, net	1,850,169	1,747,449
Mineral bearing land and leased interests
Property, Plant and Equipment [Line Items]
Property, plant and equipment	468,966	333,024
Mineral bearing land and leased interests | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	468,966	333,024
Land (non-mineral bearing)
Property, Plant and Equipment [Line Items]
Property, plant and equipment	197,432	182,065
Land (non-mineral bearing) | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	197,432	182,065
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 181,198	178,088
Buildings and improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Buildings and improvements | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 181,198	178,088
Buildings and improvements | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Buildings and improvements | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Plants, machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 1,397,410	1,318,512
Plants, machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Plants, machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Plants, machinery and equipment | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 1,397,410	1,318,512
Plants, machinery and equipment | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Plants, machinery and equipment | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Mobile equipment and barges
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 543,133	501,809
Mobile equipment and barges | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	6 years
Mobile equipment and barges | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Mobile equipment and barges | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 543,133	501,809
Mobile equipment and barges | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	6 years
Mobile equipment and barges | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Truck and auto fleet
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 56,163	54,838
Truck and auto fleet | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Truck and auto fleet | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Truck and auto fleet | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 56,163	54,838
Truck and auto fleet | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Truck and auto fleet | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Landfill airspace and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 52,202	49,766
Landfill airspace and improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Landfill airspace and improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Landfill airspace and improvements | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 52,202	49,766
Landfill airspace and improvements | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Landfill airspace and improvements | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 45,942	43,155
Office equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Office equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Office equipment | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 45,942	43,155
Office equipment | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Office equipment | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 40,648	42,007
Construction in progress | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 40,648	$ 42,007
Other | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Other | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Other | Summit Materials, LLC | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Other | Summit Materials, LLC | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years

Property, Plant and Equipment_4

Property, Plant and Equipment, net and Intangibles, net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Property, Plant and Equipment [Line Items]
Depreciation, depletion and amortization expense	$ 195,300	$ 196,800	$ 199,600
Property, plant and equipment including finance lease right-of-use asset, gross	2,983,094	2,703,264
Finance lease right-of-use asset accumulated amortization	1,132,925	955,815
Current finance lease liabilities	$ 24,601	16,007
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Long-term finance lease liabilities	$ 31,727	40,410
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
2021	$ 26,742
2022	18,603
2023	7,053
2024	3,207
2025	2,573
Gain on sale of property, plant and equipment	7,569	10,665	12,555
General and administrative expenses
Property, Plant and Equipment [Line Items]
Gain on sale of property, plant and equipment	7,600	10,700	12,600
Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Depreciation, depletion and amortization expense	195,300	196,800	199,600
Property, plant and equipment including finance lease right-of-use asset, gross	2,983,094	2,703,264
Finance lease right-of-use asset accumulated amortization	1,132,925	955,815
Current finance lease liabilities	$ 24,601	16,007
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Long-term finance lease liabilities	$ 31,727	40,410
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
2021	$ 26,742
2022	18,603
2023	7,053
2024	3,207
2025	2,573
Gain on sale of property, plant and equipment	7,569	10,665	12,555
Summit Materials, LLC | General and administrative expenses
Property, Plant and Equipment [Line Items]
Gain on sale of property, plant and equipment	7,600	10,700	$ 12,600
Equipment And Building
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	92,700	82,700
Finance lease right-of-use asset accumulated amortization	32,800	24,900
Equipment And Building | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	92,700	82,700
Finance lease right-of-use asset accumulated amortization	$ 32,800	$ 24,900
Equipment
Property, Plant and Equipment [Line Items]
Equipment lease term	5 years
Equipment | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Equipment lease term	5 years
Building
Property, Plant and Equipment [Line Items]
Equipment lease term	30 years
Building | Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Equipment lease term	30 years

Property, Plant and Equipment_5

Property, Plant and Equipment, net and Intangibles, net - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 59,716	$ 33,864
Accumulated Amortization	(11,864)	(10,366)
Net Carrying Amount	47,852	23,498
Amortization expense	2,700	2,100	$ 1,500
Estimated amortization expense
2021	3,129
2022	3,136
2023	3,003
2024	2,908
2025	2,863
Thereafter	32,813
Total	47,852	23,498
Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	59,716	33,864
Accumulated Amortization	(11,864)	(10,366)
Net Carrying Amount	47,852	23,498
Amortization expense	2,700	2,100	$ 1,500
Estimated amortization expense
2021	3,129
2022	3,136
2023	3,003
2024	2,908
2025	2,863
Thereafter	32,813
Total	47,852	23,498
Operating permits
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	33,671	6,609
Accumulated Amortization	(1,207)	(290)
Net Carrying Amount	32,464	6,319
Mineral leases
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	19,225	19,064
Accumulated Amortization	(7,571)	(6,408)
Net Carrying Amount	11,654	12,656
Mineral leases | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	19,225	19,064
Accumulated Amortization	(7,571)	(6,408)
Net Carrying Amount	11,654	12,656
Reserve rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,234	6,234
Accumulated Amortization	(2,504)	(2,248)
Net Carrying Amount	3,730	3,986
Reserve rights | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,234	6,234
Accumulated Amortization	(2,504)	(2,248)
Net Carrying Amount	3,730	3,986
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	1,000
Accumulated Amortization	0	(958)
Net Carrying Amount	0	42
Trade names | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	1,000
Accumulated Amortization	0	(958)
Net Carrying Amount	0	42
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	586	957
Accumulated Amortization	(582)	(462)
Net Carrying Amount	4	495
Other | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	586	957
Accumulated Amortization	(582)	(462)
Net Carrying Amount	$ 4	$ 495

Accrued Expenses - Components o

Accrued Expenses - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Schedule Of Accrued Expenses [Line Items]
Interest	$ 21,860	$ 26,892
Payroll and benefits	46,026	29,356
Finance lease obligations	24,601	16,007
Insurance	18,355	14,968
Non-income taxes	15,669	7,666
Deferred asset purchase payments	9,749	3,525
Professional fees	828	902
Other	23,482	20,689
Total	160,570	120,005
Summit Materials, LLC
Schedule Of Accrued Expenses [Line Items]
Interest	21,860	26,892
Payroll and benefits	46,026	29,356
Finance lease obligations	24,601	16,007
Insurance	18,355	14,968
Non-income taxes	15,900	7,898
Deferred asset purchase payments	9,749	3,525
Professional fees	828	902
Other	23,482	20,689
Total	$ 160,801	$ 120,237

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($)	Jan. 02, 2021	Dec. 28, 2019	Jun. 01, 2017
Debt
Total debt	$ 1,915,425,000	$ 1,872,273,000
Current portion of long-term debt	6,354,000	7,942,000
Long-term Debt, Excluding Current Maturities	1,909,071,000	1,864,331,000
Gross amount	1,916,314,000
Debt discount	889,000
Summit Materials, LLC
Debt
Total debt	1,915,425,000	1,872,273,000
Current portion of long-term debt	6,354,000	7,942,000
Long-term Debt, Excluding Current Maturities	1,909,071,000	1,864,331,000
Gross amount	1,916,314,000
Debt discount	889,000
Term Loan, due 2024:
Debt
Total debt	615,425,000	623,140,000
Gross amount	616,300,000	624,300,000
Debt discount	900,000	1,100,000
Term Loan, due 2024: | Summit Materials, LLC
Debt
Total debt	615,425,000	623,140,000
Gross amount	616,300,000	624,300,000
Debt discount	900,000	1,100,000
6 1⁄8% Senior Notes, due 2023:
Debt
Total debt	$ 0	649,133,000
Debt instrument interest rate (as a percent)	6.125%
Gross amount		650,000,000
Debt discount		900,000
6 1⁄8% Senior Notes, due 2023: | Summit Materials, LLC
Debt
Total debt	$ 0	649,133,000
Debt instrument interest rate (as a percent)	6.125%
Gross amount		650,000,000
Debt discount		900,000
5 1⁄8% Senior Notes, due 2025
Debt
Total debt	$ 300,000,000	300,000,000
5 1⁄8% Senior Notes, due 2025 | Summit Materials, LLC
Debt
Total debt	$ 300,000,000	300,000,000	$ 300,000,000
Debt instrument interest rate (as a percent)	5.125%		5.125%
Senior Notes | 6 1⁄2% Senior Notes, due 2027
Debt
Total debt	$ 300,000,000	300,000,000
Debt instrument interest rate (as a percent)	6.50%
Senior Notes | 6 1⁄2% Senior Notes, due 2027 | Summit Materials, LLC
Debt
Total debt	$ 300,000,000	300,000,000
Debt instrument interest rate (as a percent)	6.50%
Senior Notes | 5 1⁄4% Senior Notes, due 2029
Debt
Total debt	$ 700,000,000	0
Debt instrument interest rate (as a percent)	5.25%
Senior Notes | 5 1⁄4% Senior Notes, due 2029 | Summit Materials, LLC
Debt
Total debt	$ 700,000,000	$ 0
Debt instrument interest rate (as a percent)	5.25%

Debt - Schedule of Contractual

Debt - Schedule of Contractual Payments of Long-Term Debt (Details) $ in Thousands	Jan. 02, 2021USD ($)
Contractual payments of long-term debt
2021	$ 6,354
2022	6,354
2023	6,354
2024	597,252
2025	300,000
Thereafter	1,000,000
Total	1,916,314
Less: Original issue net discount	(889)
Less: Capitalized loan costs	(16,724)
Total debt	1,898,701
Summit Materials, LLC
Contractual payments of long-term debt
2021	6,354
2022	6,354
2023	6,354
2024	597,252
2025	300,000
Thereafter	1,000,000
Total	1,916,314
Less: Original issue net discount	(889)
Less: Capitalized loan costs	(16,724)
Total debt	$ 1,898,701

Debt - Senior Notes (Details)

Debt - Senior Notes (Details) - USD ($)	Aug. 11, 2020	Mar. 15, 2019	Jun. 01, 2017	Sep. 26, 2020	Mar. 30, 2019	Jan. 02, 2021	Dec. 28, 2019	Jan. 02, 2016	Aug. 31, 2020	Mar. 31, 2019
Debt
Long-term debt						$ 1,915,425,000	$ 1,872,273,000
Write off of deferred financing fees						3,338,000	2,850,000
5 1⁄8% Senior Notes, due 2025
Debt
Long-term debt						300,000,000	300,000,000
6 1⁄8% Senior Notes, due 2023:
Debt
Long-term debt						$ 0	649,133,000
Senior notes, interest rate (as a percent)						6.125%
Issuers | 8 1/2% Senior Notes, due 2022
Debt
Senior notes, interest rate (as a percent)										8.50%
Senior notes, aggregate principal amount redeemed										$ 250,000,000
Loss on extinguishment of debt					$ (14,600,000)
Write off of deferred financing fees					2,900,000
Prepayment premium					11,700,000
Issuers | 5 1⁄8% Senior Notes, due 2025
Debt
Long-term debt			$ 300,000,000
Senior notes, interest rate (as a percent)			5.125%
Percentage of par value of senior notes			100.00%
Proceeds net of related fees and expenses			$ 295,400,000
Issuers | 6 1⁄8% Senior Notes, due 2023:
Debt
Senior notes, interest rate (as a percent)								6.125%	6.125%
Senior notes, aggregate principal amount redeemed									$ 650,000,000
Loss on extinguishment of debt				$ (4,100,000)
Write-off of debt discount				800,000
Write off of deferred financing fees				$ 3,300,000
Debt instrument, face amount								$ 650,000,000
Issuers | 6 1/8% Senior Notes, due 2023, issued at par
Debt
Debt instrument, face amount								$ 350,000,000
Issuers | 6 1/8% Senior Notes, due 2023, , issued at 99.375% of par
Debt
Percentage of par value of senior notes								99.375%
Debt instrument, face amount								$ 300,000,000
Issuers | 5 1⁄4% Senior Notes, due 2029
Debt
Long-term debt	$ 700,000,000
Senior notes, interest rate (as a percent)	5.25%
Proceeds net of related fees and expenses	$ 690,400,000
Summit Materials, LLC
Debt
Long-term debt						$ 1,915,425,000	1,872,273,000
Write off of deferred financing fees						3,338,000	2,850,000
Summit Materials, LLC | 8 1/2% Senior Notes, due 2022
Debt
Senior notes, interest rate (as a percent)										8.50%
Senior notes, aggregate principal amount redeemed										$ 250,000,000
Loss on extinguishment of debt					(14,600,000)
Write off of deferred financing fees					2,900,000
Prepayment premium					$ 11,700,000
Summit Materials, LLC | 5 1⁄8% Senior Notes, due 2025
Debt
Long-term debt			$ 300,000,000			$ 300,000,000	300,000,000
Senior notes, interest rate (as a percent)			5.125%			5.125%
Percentage of par value of senior notes			100.00%
Proceeds net of related fees and expenses			$ 295,400,000
Summit Materials, LLC | 6 1⁄8% Senior Notes, due 2023:
Debt
Long-term debt						$ 0	649,133,000
Senior notes, interest rate (as a percent)						6.125%
Senior Notes | 6 1⁄2% Senior Notes, due 2027
Debt
Long-term debt						$ 300,000,000	300,000,000
Senior notes, interest rate (as a percent)						6.50%
Senior Notes | 5 1⁄4% Senior Notes, due 2029
Debt
Long-term debt						$ 700,000,000	0
Senior notes, interest rate (as a percent)						5.25%
Senior Notes | Issuers | 6 1⁄2% Senior Notes, due 2027
Debt
Long-term debt		$ 300,000,000
Senior notes, interest rate (as a percent)		6.50%
Percentage of par value of senior notes		100.00%
Proceeds net of related fees and expenses		$ 296,300,000
Senior Notes | Issuers | 5 1⁄4% Senior Notes, due 2029
Debt
Percentage of par value of senior notes	100.00%
Senior Notes | Summit Materials, LLC | 6 1⁄2% Senior Notes, due 2027
Debt
Long-term debt						$ 300,000,000	300,000,000
Senior notes, interest rate (as a percent)						6.50%
Senior Notes | Summit Materials, LLC | 5 1⁄4% Senior Notes, due 2029
Debt
Long-term debt						$ 700,000,000	$ 0
Senior notes, interest rate (as a percent)						5.25%

Debt - Senior Secured Credit Fa

Debt - Senior Secured Credit Facilities (Details) - Summit Materials, LLC - USD ($)	Feb. 25, 2019	Jan. 02, 2021	Dec. 28, 2019
Term Loan, due 2024:
Debt
Debt instrument, face amount		$ 650,000,000
Revolving Credit Facility
Debt
Maximum borrowing capacity	$ 345,000,000	$ 345,000,000
Basis spread on variable rate		0.25%
Amount outstanding		$ 0	$ 0
Remaining borrowing capacity		329,100,000
Revolving Credit Facility | Federal funds rate
Debt
Basis spread on variable rate	0.50%
Revolving Credit Facility | LIBOR Plus 1%
Debt
Basis spread on variable rate	2.00%
Percentage added to base rate	1.00%
Revolving Credit Facility | LIBOR
Debt
Basis spread on variable rate	3.00%
Letter of Credit
Debt
Amount outstanding		$ 15,900,000
Senior Secured Credit Facilities
Debt
First lien leverage ratio		4.75

Debt - Summary of Activity for

Debt - Summary of Activity for Deferred Financing Fees (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Deferred finance costs
Beginning balance	$ 15,436	$ 15,475
Loan origination fees	9,605	6,312
Amortization	(3,336)	(3,501)
Write off of deferred financing fees	(3,338)	(2,850)
Ending balance	18,367	15,436
Summit Materials, LLC
Deferred finance costs
Beginning balance	15,436	15,475
Loan origination fees	9,605	6,312
Amortization	(3,336)	(3,501)
Write off of deferred financing fees	(3,338)	(2,850)
Ending balance	$ 18,367	$ 15,436

Debt - Other Narrative (Details

Debt - Other Narrative (Details)	Jan. 15, 2015USD ($)	Jan. 02, 2021USD ($)	Dec. 28, 2019USD ($)	Jan. 15, 2015CAD ($)
Canadian subsidiary credit agreement, Operating activities
Debt
Revolving credit commitment				$ 6,000,000
Canadian subsidiary credit agreement, Operating activities | Summit Materials, LLC
Debt
Revolving credit commitment	$ 6,000,000
Canadian subsidiary credit agreement, Capital equipment
Debt
Revolving credit commitment				500,000
Canadian subsidiary credit agreement, Capital equipment | Summit Materials, LLC
Debt
Revolving credit commitment	500,000
Canadian subsidiary credit agreement, Guarantees
Debt
Revolving credit commitment				$ 400,000
Canadian subsidiary credit agreement, Guarantees | Summit Materials, LLC
Debt
Revolving credit commitment	$ 400,000
Canadian subsidiary credit agreement
Debt
Amount outstanding		$ 0	$ 0
Canadian subsidiary credit agreement | Summit Materials, LLC
Debt
Amount outstanding		$ 0	$ 0
Prime rate | Canadian subsidiary credit agreement, Operating activities
Debt
Basis spread on variable rate	0.20%
Prime rate | Canadian subsidiary credit agreement, Operating activities | Summit Materials, LLC
Debt
Basis spread on variable rate	0.20%
Prime rate | Canadian subsidiary credit agreement, Capital equipment
Debt
Basis spread on variable rate	0.90%
Prime rate | Canadian subsidiary credit agreement, Capital equipment | Summit Materials, LLC
Debt
Basis spread on variable rate	0.90%

Income Taxes - Components of In

Income Taxes - Components of Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Provision for income taxes:
Current	$ 3,827	$ 69	$ 463
Deferred	(16,012)	17,032	59,284
Income tax expense (benefit)	(12,185)	17,101	59,747
Summit Materials, LLC
Provision for income taxes:
Current	3,827	69	463
Deferred	(2,764)	6,316	9,810
Income tax expense (benefit)	$ 1,063	$ 6,385	$ 10,273

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Benefit (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense (benefit) at federal statutory tax rate	$ 27,100	$ 16,427	$ 20,177
Less: Income tax benefit at federal statutory tax rate for LLC entities	(593)	(658)	(561)
State and local income taxes	5,067	3,792	4,894
Permanent differences	(3,345)	(6,272)	(5,537)
Effective tax rate change	4,257	(2,006)	4,034
Unrecognized tax benefits	(41,548)	18,885	22,663
Tax receivable agreement (benefit) expense	(6)	2,436	(8,282)
Change in valuation allowance	0	(17,691)	17,592
Other	(3,117)	2,188	4,767
Income tax expense (benefit)	(12,185)	17,101	59,747
Summit Materials, LLC
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense (benefit) at federal statutory tax rate	25,577	19,947	15,563
Less: Income tax benefit at federal statutory tax rate for LLC entities	(17,647)	(15,387)	(13,863)
State and local income taxes	2,073	1,680	1,614
Permanent differences	2,479	13	(1,194)
Effective tax rate change	681	(725)	(1,148)
Unrecognized tax benefits	(11,525)	5,038	6,487
Change in valuation allowance	0	(2,478)	2,586
Other	(575)	(1,703)	228
Income tax expense (benefit)	$ 1,063	$ 6,385	$ 10,273

Income Taxes - Components of Ne

Income Taxes - Components of Net Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Deferred tax assets (liabilities):
Net intangible assets	$ 199,497	$ 240,790
Accelerated depreciation	(209,644)	(201,126)
Net operating loss	227,560	164,335
Investment in limited partnership	(33,139)	(31,987)
Mining reclamation reserve	3,306	2,018
Working capital (e.g., accrued compensation, prepaid assets)	45,972	37,287
Interest expense limitation carryforward	0	2,691
Less valuation allowance	(1,675)	(1,675)	$ (19,366)
Deferred tax assets	231,877	212,333
Less foreign deferred tax liability (included in other noncurrent liabilities)	(18,393)	(8,267)
Net deferred tax asset	213,484	204,066
Summit Materials, LLC
Deferred tax assets (liabilities):
Accelerated depreciation	(70,588)	(60,216)
Net operating loss	26,929	18,036
Investment in limited partnership	(18,931)	(17,686)
Net intangible assets	(3,264)	(2,554)
Mining reclamation reserve	1,652	723
Working capital (e.g., accrued compensation, prepaid assets)	1,590	1,366
Interest expense limitation carryforward	0	2,691
Less valuation allowance	(1,675)	(1,675)	$ (4,261)
Net deferred tax liabilities	(62,612)	(57,640)
Net deferred tax liability	$ (64,287)	$ (59,315)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 29, 2018	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Income Taxes [Line Items]
Deferred tax assets subject to TRA		$ 378,500,000
Income tax expense (benefit)		(12,185,000)	$ 17,101,000	$ 59,747,000
Reduction of net deferred tax assets due to change in statutory rate	$ 17,600,000
Unrecognized tax benefits that if recognized would affect the annual effective tax rate	22,700,000	0	41,500,000	22,700,000
Unrecognized tax benefits	22,663,000	0	41,548,000	22,663,000
Deferred tax asset, valuation allowance	19,366,000	1,675,000	1,675,000	19,366,000
Deferred tax asset, Investment in limited partnership		2,400,000	1,100,000
Tax receivable agreement (benefit) expense		(7,559,000)	16,237,000	(22,684,000)
Tax receivable agreement liability		321,680,000	326,965,000
Penalties and interest expense		0	0	0
Summit Holdings LP
Income Taxes [Line Items]
Distributions to LP Unitholders		0	100,000
Summit Materials, LLC
Income Taxes [Line Items]
Income tax expense (benefit)		1,063,000	6,385,000	10,273,000
Reduction of net deferred tax assets due to change in statutory rate				2,600,000
Unrecognized tax benefits	6,487,000	0	11,619,000	6,487,000
Net operating loss carryforwards		120,300,000
Deferred tax asset, valuation allowance	$ 4,261,000	1,675,000	1,675,000	$ 4,261,000
Penalties and interest expense		$ 0	0
Tax Receivable Agreement
Income Taxes [Line Items]
Tax receivable agreement liability			$ 327,000,000
Tax Receivable Agreement | Summit Holdings LP
Income Taxes [Line Items]
Percentage of benefits to be paid on tax receivable agreement		85.00%
Federal
Income Taxes [Line Items]
Net operating loss carryforwards		$ 917,000,000
Federal | Tax Receivable Agreement
Income Taxes [Line Items]
Net operating loss carryforwards		$ 497,000,000

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 41,548	$ 22,663
Additions based on tax position in 2018		18,885
Reductions based on new regulations	(41,548)
Unrecognized tax benefits, ending balance	0	41,548
Summit Materials, LLC
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	11,619	6,487
Additions based on tax position in 2018		5,132
Reductions based on new regulations	(11,619)
Unrecognized tax benefits, ending balance	$ 0	$ 11,619

Incomes Taxes - Deferred Tax As

Incomes Taxes - Deferred Tax Asset Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Valuation Allowance:
Beginning balance	$ (1,675)	$ (19,366)
Current year decreases (increases) from operations	0	17,691
Ending balance	(1,675)	(1,675)
Summit Materials, LLC
Valuation Allowance:
Beginning balance	(1,675)	(4,261)
Release of valuation allowance and other	0	2,586
Ending balance	$ (1,675)	$ (1,675)

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Basic to Diluted Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Reconciliation of basic to diluted loss per share
Net income attributable to Summit Inc.	$ 137,967	$ 59,066	$ 33,906
Diluted net income attributable to Summit Inc.	$ 137,967	$ 59,066	$ 33,906
LP Units
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share	3,060,248	3,372,706	3,512,669
Warrant
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share	100,037	0	0
Restricted Stock
Reconciliation of basic to diluted loss per share
Add: Nonvested restricted stock awards of retirement eligible shares (in shares)	212,443	0	0
Common Class A
Reconciliation of basic to diluted loss per share
Weighted average shares outstanding (in shares)	114,014,749	112,204,067	111,380,175
Basic (USD per share)	$ 1.21	$ 0.53	$ 0.30
Add: warrants	0	4,206	25,049
Weighted average dilutive shares outstanding (in shares)	114,631,768	112,684,718	112,316,646
Diluted (USD per share)	$ 1.20	$ 0.52	$ 0.30
Common Class A | Stock Options
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements	3,390	87,290	282,329
Common Class A | Restricted stock
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements	520,871	342,620	459,280
Common Class A | Performance Stock Units
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements	92,758	46,535	169,813
Common Class A and Restricted Stock
Reconciliation of basic to diluted loss per share
Weighted average shares outstanding (in shares)	114,227,192	112,204,067	111,380,175
Basic (USD per share)	$ 1.21	$ 0.53	$ 0.30

Stockholders' Equity_Members' I

Stockholders' Equity/Members' Interest - Narrative (Details) - $ / shares	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Common Class A
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	114,390,595	113,309,385	111,658,927
Common stock, shares outstanding (in shares)	114,390,595	113,309,385
Common Class B
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	99	99
Common stock, shares outstanding (in shares)	99	99

Stockholders' Equity_Members'_2

Stockholders' Equity/Members' Interest - Change in Ownership (Details) - shares	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Increase (Decrease) In Stockholders' Equity [Rollforward]
Stock option exercises (in shares)		1,065,446
Summit Materials Incorporated And Summit Holdings LP
Increase (Decrease) In Stockholders' Equity [Rollforward]
Beginning balance stockholders' equity (in shares)	116,559,042	115,094,445
Exchanges during period (in shares)	0	0
Stock option exercises (in shares)	54,517
Other equity transactions (in shares)	650,206	399,151
Ending balance stockholders' equity (in shares)	117,263,765	116,559,042	115,094,445
LP Units | Summit Holdings LP
Increase (Decrease) In Stockholders' Equity [Rollforward]
Number of LP Units outstanding (in shares)	3,249,657	3,435,518
Number of LP Units exchanged	(376,487)	(185,861)
Number of LP Units outstanding (in shares)	2,873,170	3,249,657	3,435,518
Common Class A
Increase (Decrease) In Stockholders' Equity [Rollforward]
Beginning balance stockholders' equity (in shares)	113,309,385	111,658,927
Exchanges during period (in shares)	376,487	185,861
Stock option exercises (in shares)	54,517	1,065,446
Other equity transactions (in shares)	650,206	399,151
Ending balance stockholders' equity (in shares)	114,390,595	113,309,385	111,658,927
Summit Materials Inc
Increase (Decrease) In Stockholders' Equity [Rollforward]
Summit Inc. Ownership Percentage	97.50%	97.20%	97.00%

Stockholders' Equity_Members'_3

Stockholders' Equity/Members' Interest - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	$ 1,444,773	$ 1,342,145
Postretirement liability adjustment, net of tax	(1,638)	(1,402)
Foreign currency translation adjustment, net of tax	3,393	3,424
Income on cash flow hedges, net of tax		(1,255)
Ending balance stockholders' equity	1,616,268	1,444,773
Change in retirement plans
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	2,171	3,573
Postretirement liability adjustment, net of tax	(1,638)	(1,402)
Ending balance stockholders' equity	533	2,171
Foreign currency translation adjustment
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	1,277	(2,147)
Foreign currency translation adjustment, net of tax	3,393	3,424
Ending balance stockholders' equity	4,670	1,277
Cash flow hedge adjustments
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	0	1,255
Income on cash flow hedges, net of tax		(1,255)
Ending balance stockholders' equity	0	0
Accumulated Other Comprehensive Income (Loss)
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	3,448	2,681
Ending balance stockholders' equity	5,203	3,448
Summit Materials, LLC
Changes in each component of accumulated other comprehensive loss
Postretirement liability adjustment, net of tax	(2,229)	(1,925)
Foreign currency translation adjustment, net of tax	4,617	4,716
Income on cash flow hedges, net of tax		(146)
Summit Materials, LLC | Change in retirement plans
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	(6,317)	(4,392)
Postretirement liability adjustment, net of tax	(2,229)	(1,925)
Ending balance stockholders' equity	(8,546)	(6,317)
Summit Materials, LLC | Foreign currency translation adjustment
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	(14,654)	(19,370)
Foreign currency translation adjustment, net of tax	4,617	4,716
Ending balance stockholders' equity	(10,037)	(14,654)
Summit Materials, LLC | Cash flow hedge adjustments
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	0	146
Income on cash flow hedges, net of tax		(146)
Ending balance stockholders' equity	0	0
Summit Materials, LLC | Accumulated Other Comprehensive Income (Loss)
Changes in each component of accumulated other comprehensive loss
Beginning balance stockholders' equity	(20,971)	(23,616)
Ending balance stockholders' equity	$ (18,583)	$ (20,971)

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Cash payments:
Interest	$ 99,551	$ 104,614	$ 103,250
Payments (refunds) for income taxes, net	1,754	(919)	3,340
Operating cash payments on operating leases	10,452	10,618
Operating cash payments on finance leases	3,132	3,051
Finance cash payments on finance leases	14,408	13,164
Non cash financing activities:
Right of use assets obtained in exchange for operating lease obligations	4,849	5,842
Right of use assets obtained in exchange for finance leases obligations	18,016	23,965
Exchange of LP Units to shares of Class A common stock	8,227	3,847	7,499
Summit Materials, LLC
Cash payments:
Interest	99,551	104,614	103,250
Payments (refunds) for income taxes, net	1,754	(919)	$ 3,340
Operating cash payments on operating leases	10,452	10,618
Operating cash payments on finance leases	3,132	3,051
Finance cash payments on finance leases	14,408	13,164
Non cash financing activities:
Right of use assets obtained in exchange for operating lease obligations	4,849	5,842
Right of use assets obtained in exchange for finance leases obligations	$ 18,016	$ 23,965

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018	Jan. 02, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 28.9	$ 20.4	$ 25.4
Dividend yield		0.00%
Unrecognized compensation cost		$ 22
Weighted average contractual term, unrecognized compensation cost		1 year 8 months 12 days
2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)					13,500,000
Shares available for grant (in shares)		4,300,000
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted during the period (in shares)		1,379,943
Intrinsic value, units outstanding		$ 42.9
Weighted average remaining contractual term		1 year
Restricted stock | 2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		1 year
Awards granted during the period (in shares)		42,736	65,144	38,232
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, granted (in shares)		0	0	0
Intrinsic value, options outstanding		$ 3.8
Weighted average remaining contractual term		3 years 3 months 18 days
Weighted average strike price, outstanding (in dollars per share)		$ 18.75
Exercisable (in shares)		2,000,000
Intrinsic value, exercisable stock options		$ 3.8
Weighted average strike price, exercisable (in dollars per share)		$ 18.75
Weighed average remaining contractual term, exercisable		3 years 3 months 18 days
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Awards granted during the period (in shares)		199,946
Intrinsic value, units outstanding		$ 8.6
Weighted average remaining contractual term		1 year 3 months 18 days
Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 28.9	$ 20.4	$ 25.4
Dividend yield		0.00%
Unrecognized compensation cost		$ 22
Weighted average contractual term, unrecognized compensation cost			1 year 8 months 12 days
Weighed average remaining contractual term, exercisable		3 years 3 months 18 days
Summit Materials, LLC | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted during the period (in shares)		1,379,943
Intrinsic value, units outstanding		$ 42.9
Weighted average remaining contractual term		1 year
Summit Materials, LLC | Restricted stock | 2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		1 year
Summit Materials, LLC | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, granted (in shares)		0	0	0
Intrinsic value, options outstanding		$ 3.8
Weighted average remaining contractual term		3 years 3 months 18 days
Weighted average strike price, outstanding (in dollars per share)		$ 18.75
Exercisable (in shares)		2,000,000
Intrinsic value, exercisable stock options		$ 3.8
Weighted average strike price, exercisable (in dollars per share)		$ 18.75
Summit Materials, LLC | Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Awards granted during the period (in shares)		199,946
Intrinsic value, units outstanding		$ 8.6
Weighted average remaining contractual term		1 year 3 months 18 days
Summit Holdings LP | Leverage restoration options, time-vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1
Minimum | Restricted stock | 2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		2 years
Minimum | Summit Materials, LLC | Restricted stock | 2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		2 years
Maximum | Restricted stock | 2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Maximum | Summit Materials, LLC | Restricted stock | 2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Award Activity (Details) - $ / shares	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Exercised (in shares)		(1,065,446)
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)	2,128,107
Options, Granted (in shares)	0	0	0
Options, Forfeited/Canceled (in shares)	(35,117)
Options, Exercised (in shares)	(54,517)
Options, Vested	0
Options, Ending balance (in shares)	2,038,473	2,128,107
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options, Beginning balance (in dollars per share)	$ 9.08
Options, Granted (in dollars per share)	0
Options, Forfeited/Canceled (in dollars per share)	12.30
Options, Exercised (in dollars per share)	10.10
Options, Vested (in dollars per share)	0
Options, Ending balance (in dollars per share)	$ 9.16	$ 9.08
Stock Options | Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)	2,128,107
Options, Granted (in shares)	0	0	0
Options, Forfeited/Canceled (in shares)	(35,117)
Options, Exercised (in shares)	(54,517)
Options, Vested	0
Options, Ending balance (in shares)	2,038,473	2,128,107
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options, Beginning balance (in dollars per share)	$ 9.08
Options, Granted (in dollars per share)	0
Options, Forfeited/Canceled (in dollars per share)	12.30
Options, Exercised (in dollars per share)	10.10
Options, Vested (in dollars per share)	0
Options, Ending balance (in dollars per share)	$ 9.16	$ 9.08
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of units, Beginning balance (in shares)	1,556,636
Number of units, granted (in shares)	1,379,943
Number of units, Forfeited/Canceled (in shares)	(154,283)
Number of units, Exercised (in shares)	0
Number of units, Vested (in shares)	(647,345)
Number of units, Ending balance (in shares)	2,134,951	1,556,636
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of units, Beginning balance (in dollars per share)	$ 20.29
Number of units, Granted (in dollars per share)	18.10
Number of units, Forfeited/Canceled (in dollars per share)	19.12
Number of units, Exercised (in dollars per share)	0
Number of units, Vested (in dollars per share)	21.28
Number of units, Ending balance (in dollars per share)	$ 18.64	$ 20.29
Restricted stock | Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of units, Beginning balance (in shares)	1,556,636
Number of units, granted (in shares)	1,379,943
Number of units, Forfeited/Canceled (in shares)	(154,283)
Number of units, Exercised (in shares)	0
Number of units, Vested (in shares)	(647,345)
Number of units, Ending balance (in shares)	2,134,951	1,556,636
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of units, Beginning balance (in dollars per share)	$ 20.29
Number of units, Granted (in dollars per share)	18.10
Number of units, Forfeited/Canceled (in dollars per share)	19.12
Number of units, Exercised (in dollars per share)	0
Number of units, Vested (in dollars per share)	21.28
Number of units, Ending balance (in dollars per share)	$ 18.64	$ 20.29
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of units, Beginning balance (in shares)	390,645
Number of units, granted (in shares)	199,946
Number of units, Forfeited/Canceled (in shares)	(112,416)
Number of units, Exercised (in shares)	0
Number of units, Vested (in shares)	(49,300)
Number of units, Ending balance (in shares)	428,875	390,645
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of units, Beginning balance (in dollars per share)	$ 31.08
Number of units, Granted (in dollars per share)	23.43
Number of units, Forfeited/Canceled (in dollars per share)	26.54
Number of units, Exercised (in dollars per share)	0
Number of units, Vested (in dollars per share)	32
Number of units, Ending balance (in dollars per share)	$ 28.64	$ 31.08
Performance Stock Units | Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of units, Beginning balance (in shares)	390,645
Number of units, granted (in shares)	199,946
Number of units, Forfeited/Canceled (in shares)	(112,416)
Number of units, Exercised (in shares)	0
Number of units, Vested (in shares)	(49,300)
Number of units, Ending balance (in shares)	428,875	390,645
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of units, Beginning balance (in dollars per share)	$ 31.08
Number of units, Granted (in dollars per share)	23.43
Number of units, Forfeited/Canceled (in dollars per share)	26.54
Number of units, Exercised (in dollars per share)	0
Number of units, Vested (in dollars per share)	32
Number of units, Ending balance (in dollars per share)	$ 28.64	$ 31.08
Warrants
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of units, Beginning balance (in shares)	100,037
Number of units, granted (in shares)	0
Number of units, Forfeited/Canceled (in shares)	0
Number of units, Exercised (in shares)	0
Number of units, Vested (in shares)	0
Number of units, Ending balance (in shares)	100,037	100,037
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of units, Beginning balance (in dollars per share)	$ 18
Number of units, Granted (in dollars per share)	0
Number of units, Forfeited/Canceled (in dollars per share)	0
Number of units, Exercised (in dollars per share)	0
Number of units, Vested (in dollars per share)	0
Number of units, Ending balance (in dollars per share)	$ 18	$ 18
Warrants | Summit Materials, LLC
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of units, Beginning balance (in shares)	100,037
Number of units, granted (in shares)	0
Number of units, Forfeited/Canceled (in shares)	0
Number of units, Exercised (in shares)	0
Number of units, Vested (in shares)	0
Number of units, Ending balance (in shares)	100,037	100,037
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Number of units, Beginning balance (in dollars per share)	$ 18
Number of units, Granted (in dollars per share)	0
Number of units, Forfeited/Canceled (in dollars per share)	0
Number of units, Exercised (in dollars per share)	0
Number of units, Vested (in dollars per share)	0
Number of units, Ending balance (in dollars per share)	$ 18	$ 18

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) $ in Millions	12 Months Ended
	Jan. 02, 2021USD ($)plan	Dec. 28, 2019USD ($)	Dec. 29, 2018USD ($)	Jan. 02, 2016plan
Defined Benefit Plan Disclosure [Line Items]
Expense for defined contribution plans	$ 12.1	$ 11.7	$ 11.2
Number of noncontributory defined benefit pension plans | plan	2
Number of unfunded healthcare and life insurance benefit plans | plan	2
Number of unfunded healthcare plans for benefits prior to medicare eligibility | plan				1
Assumed health care cost trend rates	8.00%	8.00%
Assumed health care cost, grading	4.50%	4.50%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected contributions in 2021	$ 1.2
Healthcare & Life Ins
Defined Benefit Plan Disclosure [Line Items]
Expected contributions in 2021	0.6
Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Expense for defined contribution plans	$ 12.1	$ 11.7	$ 11.2
Assumed health care cost trend rates	8.00%	8.00%
Assumed health care cost, grading	4.50%	4.50%
Summit Materials, LLC | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected contributions in 2021	$ 1.2
Summit Materials, LLC | Healthcare & Life Ins
Defined Benefit Plan Disclosure [Line Items]
Expected contributions in 2021	$ 0.6
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	30.00%
Equity Securities | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Target allocation	30.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	63.00%
Fixed Income Securities | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Target allocation	63.00%
Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation	5.00%
Cash | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Target allocation	5.00%
Precious metals
Defined Benefit Plan Disclosure [Line Items]
Target allocation	2.00%
Precious metals | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Target allocation	2.00%

Employee Benefit Plans - Obliga

Employee Benefit Plans - Obligations and Funded Status (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Change in fair value of plan assets:
Beginning of period	$ 18,242
End of period	19,058	$ 18,242
Summit Materials, LLC
Change in fair value of plan assets:
Beginning of period	18,242
End of period	19,058	18,242
Pension Benefits
Change in benefit obligations:
Beginning of period	26,181	24,203
Service cost	71	60	$ 67
Interest cost	733	928	898
Actuarial (gain) loss	2,425	2,571
Benefits paid	(1,583)	(1,581)
End of period	27,827	26,181	24,203
Change in fair value of plan assets:
Beginning of period	18,242	17,449
Actual return on plan assets	1,916	2,055
Employer contributions	483	319
Benefits paid	(1,583)	(1,581)
End of period	19,058	18,242	17,449
Funded status of plans	(8,769)	(7,939)
Current liabilities	0	0
Noncurrent liabilities	(8,769)	(7,939)
Liability recognized	(8,769)	(7,939)
Amounts recognized in accumulated other comprehensive income:
Net actuarial (gain) loss	10,689	9,286
Prior service cost	0	0
Total amount recognized	10,689	9,286
Pension Benefits | Summit Materials, LLC
Change in benefit obligations:
Beginning of period	26,181	24,203
Service cost	71	60	67
Interest cost	733	928	898
Actuarial (gain) loss	2,425	2,571
Benefits paid	(1,583)	(1,581)
End of period	27,827	26,181	24,203
Change in fair value of plan assets:
Beginning of period	18,242	17,449
Actual return on plan assets	1,916	2,055
Employer contributions	483	319
Benefits paid	(1,583)	(1,581)
End of period	19,058	18,242	17,449
Funded status of plans	(8,769)	(7,939)
Current liabilities	0	0
Noncurrent liabilities	(8,769)	(7,939)
Liability recognized	(8,769)	(7,939)
Amounts recognized in accumulated other comprehensive income:
Net actuarial (gain) loss	10,689	9,286
Prior service cost	0	0
Total amount recognized	10,689	9,286
Healthcare & Life Ins
Change in benefit obligations:
Beginning of period	9,090	9,203
Service cost	176	166	170
Interest cost	242	321	317
Actuarial (gain) loss	676	165
Benefits paid	(955)	(765)
End of period	9,229	9,090	9,203
Change in fair value of plan assets:
Beginning of period	0	0
Actual return on plan assets	0	0
Employer contributions	955	765
Benefits paid	(955)	(765)
End of period	0	0	0
Funded status of plans	(9,229)	(9,090)
Current liabilities	(636)	(653)
Noncurrent liabilities	(8,593)	(8,437)
Liability recognized	(9,229)	(9,090)
Amounts recognized in accumulated other comprehensive income:
Net actuarial (gain) loss	2,707	2,121
Prior service cost	(1,690)	(1,931)
Total amount recognized	1,017	190
Healthcare & Life Ins | Summit Materials, LLC
Change in benefit obligations:
Beginning of period	9,090	9,203
Service cost	176	166	170
Interest cost	242	321	317
Actuarial (gain) loss	676	165
Benefits paid	(955)	(765)
End of period	9,229	9,090	9,203
Change in fair value of plan assets:
Beginning of period	0	0
Actual return on plan assets	0	0
Employer contributions	955	765
Benefits paid	(955)	(765)
End of period	0	0	$ 0
Funded status of plans	(9,229)	(9,090)
Current liabilities	(636)	(653)
Noncurrent liabilities	(8,593)	(8,437)
Liability recognized	(9,229)	(9,090)
Amounts recognized in accumulated other comprehensive income:
Net actuarial (gain) loss	2,707	2,121
Prior service cost	(1,690)	(1,931)
Total amount recognized	$ 1,017	$ 190

Employee Benefit Plans - Amount

Employee Benefit Plans - Amounts Recognized in Other Comprehensive (Gain) Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Pension Benefits
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	$ 1,728	$ 1,760	$ (1,300)
Amortization of prior year service cost	0	0	0
Amortization of gain	(326)	(202)	(312)
Total amount recognized	1,402	1,558	(1,612)
Pension Benefits | Summit Materials, LLC
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	1,728	1,760	(1,300)
Amortization of prior year service cost	0	0	0
Amortization of gain	(326)	(202)	(312)
Total amount recognized	1,402	1,558	(1,612)
Healthcare & Life Ins
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	675	165	(172)
Amortization of prior year service cost	241	241	241
Amortization of gain	(89)	(39)	(118)
Total amount recognized	827	367	(49)
Healthcare & Life Ins | Summit Materials, LLC
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	675	165	(172)
Amortization of prior year service cost	241	241	241
Amortization of gain	(89)	(39)	(118)
Total amount recognized	$ 827	$ 367	$ (49)

Employee Benefit Plans - Compon

Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 71	$ 60	$ 67
Interest cost	733	928	898
Amortization of gain	326	202	312
Expected return on plan assets	(1,221)	(1,244)	(1,284)
Amortization of prior service credit	0	0	0
Net periodic (expense) benefit cost	(91)	(54)	(7)
Pension Benefits | Summit Materials, LLC
Components of net periodic benefit cost:
Service cost	71	60	67
Interest cost	733	928	898
Amortization of gain	326	202	312
Expected return on plan assets	(1,221)	(1,244)	(1,284)
Amortization of prior service credit	0	0	0
Net periodic (expense) benefit cost	(91)	(54)	(7)
Healthcare & Life Ins
Components of net periodic benefit cost:
Service cost	176	166	170
Interest cost	242	321	317
Amortization of gain	89	39	118
Expected return on plan assets	0	0	0
Amortization of prior service credit	(241)	(241)	(241)
Net periodic (expense) benefit cost	266	285	364
Healthcare & Life Ins | Summit Materials, LLC
Components of net periodic benefit cost:
Service cost	176	166	170
Interest cost	242	321	317
Amortization of gain	89	39	118
Expected return on plan assets	0	0	0
Amortization of prior service credit	(241)	(241)	(241)
Net periodic (expense) benefit cost	$ 266	$ 285	$ 364

Employee Benefit Plans - Weight

Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Benefit Obligations (Detail)	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets, benefit obligation	7.00%	7.00%
Pension Benefits | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets, benefit obligation	7.00%	7.00%
Pension Benefits | Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.84%	2.78%
Pension Benefits | Minimum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.84%	2.78%
Pension Benefits | Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.14%	2.96%
Pension Benefits | Maximum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.14%	2.96%
Healthcare & Life Ins | Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.80%	2.73%
Healthcare & Life Ins | Minimum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.80%	2.73%
Healthcare & Life Ins | Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.82%	2.79%
Healthcare & Life Ins | Maximum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.82%	2.79%

Employee Benefit Plans - Weig_2

Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail)	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets, net periodic benefit cost	7.00%	7.00%	7.00%
Pension Benefits | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets, net periodic benefit cost	7.00%	7.00%	7.00%
Pension Benefits | Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.78%	3.90%	3.23%
Pension Benefits | Minimum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.78%	3.90%	3.23%
Pension Benefits | Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.96%	4.02%	3.37%
Pension Benefits | Maximum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.96%	4.02%	3.37%
Healthcare & Life Ins | Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.73%	3.87%	3.20%
Healthcare & Life Ins | Minimum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.73%	3.87%	3.20%
Healthcare & Life Ins | Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.79%	3.91%	3.25%
Healthcare & Life Ins | Maximum | Summit Materials, LLC
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.79%	3.91%	3.25%

Employee Benefit Plans - Fair V

Employee Benefit Plans - Fair Value of Company's Pension Plans' Assets (Detail) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	$ 19,058	$ 18,242
Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	19,058	18,242
Intermediate—government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,294	2,482
Intermediate—government | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,294	2,482
Intermediate—corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,218	1,066
Intermediate—corporate | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,218	1,066
Short-term—government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	705	1,387
Short-term—government | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	705	1,387
Short-term—corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	448	3,173
Short-term—corporate | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	448	3,173
International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,086	1,387
International | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,086	1,387
U.S. Large cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,516	1,225
U.S. Large cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,516	1,225
U.S. Large cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,483	1,167
U.S. Large cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,483	1,167
U.S. Mid cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	631	581
U.S. Mid cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	631	581
U.S. Mid cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	619	578
U.S. Mid cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	619	578
U.S. Small cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	663	583
U.S. Small cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	663	583
U.S. Small cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	650	593
U.S. Small cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	650	593
Managed Futures
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value		340
Managed Futures | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value		340
International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,227	1,174
International | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,227	1,174
Emerging Markets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	409	394
Emerging Markets | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	409	394
Commodities Broad Basket
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,002	1,118
Commodities Broad Basket | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,002	1,118
Cash
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	2,107	994
Cash | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	2,107	994
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	12,666	10,732
Quoted Prices in Active Markets for Identical Assets (Level 1) | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	12,666	10,732
Quoted Prices in Active Markets for Identical Assets (Level 1) | Intermediate—government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,294	2,482
Quoted Prices in Active Markets for Identical Assets (Level 1) | Intermediate—government | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,294	2,482
Quoted Prices in Active Markets for Identical Assets (Level 1) | Intermediate—corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Intermediate—corporate | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term—government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	705	1,387
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term—government | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	705	1,387
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term—corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term—corporate | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | International | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Large cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,516	1,225
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Large cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,516	1,225
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Large cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,483	1,167
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Large cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,483	1,167
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Mid cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	631	581
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Mid cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	631	581
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Mid cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	619	578
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Mid cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	619	578
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Small cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	663	583
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Small cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	663	583
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Small cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	650	593
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Small cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	650	593
Quoted Prices in Active Markets for Identical Assets (Level 1) | Managed Futures
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Managed Futures | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	407	386
Quoted Prices in Active Markets for Identical Assets (Level 1) | International | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	407	386
Quoted Prices in Active Markets for Identical Assets (Level 1) | Emerging Markets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	409	394
Quoted Prices in Active Markets for Identical Assets (Level 1) | Emerging Markets | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	409	394
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodities Broad Basket
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	182	362
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodities Broad Basket | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	182	362
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	2,107	994
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	2,107	994
Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	6,392	7,510
Observable Inputs (Level 2) | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	6,392	7,510
Observable Inputs (Level 2) | Intermediate—government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Intermediate—government | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Intermediate—corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,218	1,066
Observable Inputs (Level 2) | Intermediate—corporate | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	3,218	1,066
Observable Inputs (Level 2) | Short-term—government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Short-term—government | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Short-term—corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	448	3,173
Observable Inputs (Level 2) | Short-term—corporate | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	448	3,173
Observable Inputs (Level 2) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,086	1,387
Observable Inputs (Level 2) | International | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	1,086	1,387
Observable Inputs (Level 2) | U.S. Large cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Large cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Large cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Large cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Mid cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Mid cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Mid cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Mid cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Small cap value
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Small cap value | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Small cap growth
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | U.S. Small cap growth | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Managed Futures
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value		340
Observable Inputs (Level 2) | Managed Futures | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value		340
Observable Inputs (Level 2) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	820	788
Observable Inputs (Level 2) | International | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	820	788
Observable Inputs (Level 2) | Emerging Markets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Emerging Markets | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Commodities Broad Basket
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	820	756
Observable Inputs (Level 2) | Commodities Broad Basket | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	820	756
Observable Inputs (Level 2) | Cash
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	0	0
Observable Inputs (Level 2) | Cash | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value	$ 0	$ 0

Employee Benefit Plans - Estima

Employee Benefit Plans - Estimated Benefit Payments (Detail) $ in Thousands	Jan. 02, 2021USD ($)
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2021	$ 1,692
2022	1,693
2023	1,696
2024	1,655
2025	1,613
2026 - 2030	7,597
Pension Benefits | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2021	1,692
2022	1,693
2023	1,696
2024	1,655
2025	1,613
2026 - 2030	7,597
Healthcare & Life Ins
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2021	636
2022	630
2023	617
2024	619
2025	627
2026 - 2030	3,139
Healthcare & Life Ins | Summit Materials, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2021	636
2022	630
2023	617
2024	619
2025	627
2026 - 2030	$ 3,139

Employee Benefit Plans - Multie

Employee Benefit Plans - Multiemployer Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Multiemployer Plans [Line Items]
Contributions of Company	$ 120	$ 135
Construction Industry Laborers Pension Fund
Multiemployer Plans [Line Items]
Contributions of Company	100	112
Operating Engineers Local 101 Pension Plan
Multiemployer Plans [Line Items]
Contributions of Company	20	23
Summit Materials, LLC
Multiemployer Plans [Line Items]
Contributions of Company	120	135
Summit Materials, LLC | Construction Industry Laborers Pension Fund
Multiemployer Plans [Line Items]
Contributions of Company	100	112
Summit Materials, LLC | Operating Engineers Local 101 Pension Plan
Multiemployer Plans [Line Items]
Contributions of Company	$ 20	$ 23

Accrued Mining and Landfill R_3

Accrued Mining and Landfill Reclamation - Narrative (Detail) - USD ($) $ in Millions	Jan. 02, 2021	Dec. 28, 2019
Asset Retirement Obligations [Line Items]
Anticipated costs	$ 112.8	$ 97.4
Accrued expenses
Asset Retirement Obligations [Line Items]
Asset retirement obligation, current	10	7.9
Summit Materials, LLC
Asset Retirement Obligations [Line Items]
Anticipated costs	112.8	97.4
Summit Materials, LLC | Accrued expenses
Asset Retirement Obligations [Line Items]
Asset retirement obligation, current	$ 10	$ 7.9

Accrued Mining and Landfill R_4

Accrued Mining and Landfill Reclamation - Activity for Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Asset Retirement Obligation, Activity
Beginning balance	$ 36,676	$ 30,999
Acquired obligations	861	805
Change in cost estimate	6,523	4,468
Settlement of reclamation obligations	(3,095)	(1,812)
Accretion expense	2,638	2,216	$ 1,605
Ending balance	43,603	36,676	30,999
Summit Materials, LLC
Asset Retirement Obligation, Activity
Beginning balance	36,676	30,999
Acquired obligations	861	805
Change in cost estimate	6,523	4,468
Settlement of reclamation obligations	(3,095)	(1,812)
Accretion expense	2,638	2,216	1,605
Ending balance	$ 43,603	$ 36,676	$ 30,999

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	12 Months Ended
	Jan. 02, 2021
Loss Contingencies [Line Items]
Term of purchase commitments	1 year
Summit Materials, LLC
Loss Contingencies [Line Items]
Term of purchase commitments	1 year

Leases - Operating and Finance

Leases - Operating and Finance Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Lease, Cost [Abstract]
Operating lease cost	$ 10,134	$ 10,451
Variable lease cost	316	423
Short-term lease cost	44,066	38,417
Financing lease cost:
Amortization of right-of-use assets	12,598	11,062
Interest on lease liabilities	3,068	3,171
Total lease cost	70,182	63,524
Operating leases:
Operating lease right-of-use assets	28,543	32,777
Current operating lease liabilities	8,188	8,427
Noncurrent operating lease liabilities	21,500	25,381
Total operating lease liabilities	29,688	33,808
Finance leases:
Property and equipment, gross	92,679	82,660
Less accumulated depreciation	$ (32,828)	(24,907)
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization
Property and equipment, net	$ 59,851	57,753
Current finance lease liabilities	24,601	16,007
Long-term finance lease liabilities	31,727	40,410
Total finance lease liabilities	$ 56,328	$ 56,417
Weighted average remaining lease term (years):
Operating leases	8 years 8 months 12 days	8 years 7 months 6 days
Finance lease	2 years 4 months 24 days	2 years 7 months 6 days
Weighted average discount rate:
Operating leases	5.30%	5.50%
Finance lease	5.20%	5.50%
Operating Leases
2021	$ 9,491
2022	6,088
2023	4,663
2024	2,863
2025	1,781
Thereafter	12,961
Total lease payments	37,847
Less imputed interest	(8,159)
Finance Leases
2021	26,742
2022	18,603
2023	7,053
2024	3,207
2025	2,573
Thereafter	2,831
Total lease payments	61,009
Less imputed interest	(4,681)
Summit Materials, LLC
Lease, Cost [Abstract]
Operating lease cost	10,134	$ 10,451
Variable lease cost	316	423
Short-term lease cost	44,066	38,417
Financing lease cost:
Amortization of right-of-use assets	12,598	11,062
Interest on lease liabilities	3,068	3,171
Total lease cost	70,182	63,524
Operating leases:
Operating lease right-of-use assets	28,543	32,777
Current operating lease liabilities	8,188	8,427
Noncurrent operating lease liabilities	21,500	25,381
Total operating lease liabilities	29,688	33,808
Finance leases:
Property and equipment, gross	92,679	82,660
Less accumulated depreciation	$ (32,828)	(24,907)
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization
Property and equipment, net	$ 59,851	57,753
Current finance lease liabilities	24,601	16,007
Long-term finance lease liabilities	31,727	40,410
Total finance lease liabilities	$ 56,328	$ 56,417
Weighted average remaining lease term (years):
Operating leases	8 years 8 months 12 days	8 years 7 months 6 days
Finance lease	2 years 4 months 24 days	2 years 7 months 6 days
Weighted average discount rate:
Operating leases	5.30%	5.50%
Finance lease	5.20%	5.50%
Operating Leases
2021	$ 9,491
2022	6,088
2023	4,663
2024	2,863
2025	1,781
Thereafter	12,961
Total lease payments	37,847
Less imputed interest	(8,159)
Finance Leases
2021	26,742
2022	18,603
2023	7,053
2024	3,207
2025	2,573
Thereafter	2,831
Total lease payments	61,009
Less imputed interest	$ (4,681)

Leases - Narrative (Detail)

Leases - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Operating Leased Assets [Line Items]
Royalty expense recorded in cost of revenue	$ 29.2	$ 24.3	$ 20.1
Summit Materials, LLC
Operating Leased Assets [Line Items]
Royalty expense recorded in cost of revenue	$ 29.2	$ 24.3	$ 20.1

Leases - Schedule of Minimum Co

Leases - Schedule of Minimum Contractual Agreements Under Royalty Agreements (Details) $ in Thousands	Jan. 02, 2021USD ($)
Royalty Agreements
2021	$ 9,916
2022	9,880
2023	9,594
2024	9,295
2025	9,052
Summit Materials, LLC
Royalty Agreements
2021	9,916
2022	9,880
2023	9,594
2024	9,295
2025	$ 9,052

Fair Value of Financial Instr_2

Fair Value of Financial Instruments - Fair Value Measurements (Details) - Level 3 - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of acquisition-related liabilities and Accrued expenses - Contingent consideration	$ 654	$ 1,967
Acquisition-related liabilities and Other noncurrent liabilities - Contingent consideration	1,209	1,302
Summit Materials, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of acquisition-related liabilities and Accrued expenses - Contingent consideration	654	1,967
Acquisition-related liabilities and Other noncurrent liabilities - Contingent consideration	$ 1,209	$ 1,302

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Carrying Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019
Financial Instruments
Current portion of debt	$ 6,354	$ 7,942
Summit Materials, LLC
Financial Instruments
Current portion of debt	6,354	7,942
Level 1
Financial Instruments
Current portion of debt		7,900
Level 1 | Fair Value
Financial Instruments
Long-term debt	1,971,087	1,918,720
Current portion of debt	6,400
Level 1 | Carrying Value
Financial Instruments
Long-term debt	1,915,425	1,872,273
Level 1 | Summit Materials, LLC
Financial Instruments
Current portion of debt	6,400	7,900
Level 1 | Summit Materials, LLC | Fair Value
Financial Instruments
Long-term debt	1,971,087	1,918,720
Level 1 | Summit Materials, LLC | Carrying Value
Financial Instruments
Long-term debt	1,915,425	1,872,273
Level 3 | Fair Value
Financial Instruments
Current portion of deferred consideration and noncompete obligations	9,611	30,733
Long term portion of deferred consideration and noncompete obligations	11,037	18,499
Level 3 | Carrying Value
Financial Instruments
Current portion of deferred consideration and noncompete obligations	9,611	30,733
Long term portion of deferred consideration and noncompete obligations	11,037	18,499
Level 3 | Summit Materials, LLC | Fair Value
Financial Instruments
Current portion of deferred consideration and noncompete obligations	7,173	28,233
Long term portion of deferred consideration and noncompete obligations	11,037	16,364
Level 3 | Summit Materials, LLC | Carrying Value
Financial Instruments
Current portion of deferred consideration and noncompete obligations	7,173	28,233
Long term portion of deferred consideration and noncompete obligations	$ 11,037	$ 16,364

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Narrative (Details) - Discount Rate - Level 3	Jan. 02, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.095
Summit Materials, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.095

Segment Information - Narrative

Segment Information - Narrative (Details)	12 Months Ended
	Jan. 02, 2021segment
Segment Reporting Information [Line Items]
Number of operating segments	3
Number of reportable segments	3
Summit Materials, LLC
Segment Reporting Information [Line Items]
Number of operating segments	3
Number of reportable segments	3

Segment Information - Financial

Segment Information - Financial Data (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Segment Reporting Information [Line Items]
Revenue	$ 2,332,451	$ 2,222,140	$ 2,101,002
Income from operations before taxes	129,055	78,224	96,077
Interest expense	103,595	116,509	116,548
Depreciation, depletion and amortization	218,682	214,886	203,305
Accretion	2,638	2,216	1,605
Loss on debt financings	4,064	14,565	149
Tax receivable agreement (benefit) expense	(7,559)	16,237	(22,684)
Gain on sale of business	0	0	(12,108)
Transaction costs	2,747	2,222	4,238
Non-cash compensation	28,857	20,403	25,378
Other	2,957	(3,800)	(6,247)
Total Adjusted EBITDA	485,036	461,462	406,261
Total purchases of property, plant and equipment	177,249	177,495	220,685
Total depreciation, depletion, amortization and accretion	221,320	217,102	204,910
Total assets	4,308,011	4,067,556	3,857,641
Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment	175,099	174,982	213,077
Total depreciation, depletion, amortization and accretion	217,338	213,106	202,288
Total assets	3,657,959	3,537,047	3,501,727
Corporate and other
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(41,247)	(34,565)	(32,164)
Total purchases of property, plant and equipment	2,150	2,513	7,608
Total depreciation, depletion, amortization and accretion	3,982	3,996	2,622
Total assets	650,052	530,509	355,914
West
Segment Reporting Information [Line Items]
Revenue	1,262,196	1,122,338	1,117,066
West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	271,052	204,964	188,999
Total purchases of property, plant and equipment	67,500	71,397	120,657
Total depreciation, depletion, amortization and accretion	93,866	93,256	91,794
Total assets	1,503,382	1,379,684	1,370,501
East
Segment Reporting Information [Line Items]
Revenue	799,633	809,098	703,147
East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	162,275	187,625	138,032
Total purchases of property, plant and equipment	92,528	77,894	64,384
Total depreciation, depletion, amortization and accretion	86,205	81,403	75,433
Total assets	1,303,742	1,288,835	1,253,640
Cement
Segment Reporting Information [Line Items]
Revenue	270,622	290,704	280,789
Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	92,956	103,438	111,394
Total purchases of property, plant and equipment	15,071	25,691	28,036
Total depreciation, depletion, amortization and accretion	37,267	38,447	35,061
Total assets	850,835	868,528	877,586
Summit Materials, LLC
Segment Reporting Information [Line Items]
Revenue	2,332,451	2,222,140	2,101,002
Income from operations before taxes	121,800	94,982	74,110
Interest expense	103,291	115,988	115,831
Depreciation, depletion and amortization	218,682	214,886	203,305
Accretion	2,638	2,216	1,605
Loss on debt financings	4,064	14,565	149
Gain on sale of business	0	0	(12,108)
Transaction costs	2,747	2,222	4,238
Non-cash compensation	28,857	20,403	25,378
Other	2,957	(3,800)	(6,247)
Total Adjusted EBITDA	485,036	461,462	406,261
Total purchases of property, plant and equipment	177,249	177,495	220,685
Total depreciation, depletion, amortization and accretion	221,320	217,102	204,910
Total assets	4,077,134	3,856,223	3,633,244
Summit Materials, LLC | Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment	175,099	174,982	213,077
Total depreciation, depletion, amortization and accretion	217,338	213,106	202,288
Total assets	3,657,959	3,537,047	3,501,727
Summit Materials, LLC | Corporate and other
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(41,247)	(34,565)	(32,164)
Total purchases of property, plant and equipment	2,150	2,513	7,608
Total depreciation, depletion, amortization and accretion	3,982	3,996	2,622
Total assets	419,175	319,176	131,517
Summit Materials, LLC | West
Segment Reporting Information [Line Items]
Revenue	1,262,196	1,122,338	1,117,066
Summit Materials, LLC | West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	271,052	204,964	188,999
Total purchases of property, plant and equipment	67,500	71,397	120,657
Total depreciation, depletion, amortization and accretion	93,866	93,256	91,794
Total assets	1,503,382	1,379,684	1,370,501
Summit Materials, LLC | East
Segment Reporting Information [Line Items]
Revenue	799,633	809,098	703,147
Summit Materials, LLC | East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	162,275	187,625	138,032
Total purchases of property, plant and equipment	92,528	77,894	64,384
Total depreciation, depletion, amortization and accretion	86,205	81,403	75,433
Total assets	1,303,742	1,288,835	1,253,640
Summit Materials, LLC | Cement
Segment Reporting Information [Line Items]
Revenue	270,622	290,704	280,789
Summit Materials, LLC | Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	92,956	103,438	111,394
Total purchases of property, plant and equipment	15,071	25,691	28,036
Total depreciation, depletion, amortization and accretion	37,267	38,447	35,061
Total assets	$ 850,835	$ 868,528	$ 877,586

Senior Notes' Guarantor and N_3

Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Thousands	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Current assets:
Cash and cash equivalents	$ 418,181	$ 311,319
Accounts receivable, net	254,696	253,256
Costs and estimated earnings in excess of billings	8,666	13,088
Inventories	200,308	204,787
Other current assets	11,428	13,831
Total current assets	893,279	796,281
Property, plant and equipment including finance lease right-of-use assets, net	1,850,169	1,747,449
Goodwill	1,201,291	1,199,699	$ 1,192,028
Intangible assets, net	47,852	23,498
Operating lease right-of-use assets	28,543	32,777
Other assets	55,000	55,519
Total assets	4,308,011	4,067,556	3,857,641
Current liabilities:
Current portion of debt	6,354	7,942
Current portion of acquisition-related liabilities	10,265	32,700
Accounts payable	120,813	116,359
Accrued expenses	160,570	120,005
Current operating lease liabilities	8,188	8,427
Billings in excess of costs and estimated earnings	16,499	13,864
Total current liabilities	322,689	299,297
Long-term debt	1,892,347	1,851,057
Acquisition-related liabilities	12,246	19,801
Noncurrent operating lease liabilities	21,500	25,381
Other noncurrent liabilities	121,281	100,282
Total liabilities	2,691,743	2,622,783
Total liabilities and stockholders' equity / member's interest	4,308,011	4,067,556
Summit Materials, LLC
Current assets:
Cash and cash equivalents	418,181	311,319
Accounts receivable, net	254,696	253,256
Intercompany receivables	0	0
Costs and estimated earnings in excess of billings	8,666	13,088
Inventories	200,308	204,787
Other current assets	11,428	13,831
Total current assets	893,279	796,281
Property, plant and equipment including finance lease right-of-use assets, net	1,850,169	1,747,449
Goodwill	1,202,291	1,200,699	1,193,028
Intangible assets, net	47,852	23,498
Operating lease right-of-use assets	28,543	32,777
Other assets	55,000	55,519
Total assets	4,077,134	3,856,223	3,633,244
Current liabilities:
Current portion of debt	6,354	7,942
Current portion of acquisition-related liabilities	7,827	30,200
Accounts payable	121,422	116,970
Accrued expenses	160,801	120,237
Current operating lease liabilities	8,188	8,427
Intercompany payables	0	0
Billings in excess of costs and estimated earnings	16,499	13,864
Total current liabilities	321,091	297,640
Long-term debt	1,892,347	1,851,057
Acquisition-related liabilities	12,246	17,666
Noncurrent operating lease liabilities	21,500	25,381
Other noncurrent liabilities	167,182	151,329
Total liabilities	2,414,366	2,343,073
Total member's interest	1,662,768	1,513,150	$ 1,385,431	$ 1,291,594
Total liabilities and stockholders' equity / member's interest	4,077,134	3,856,223
Summit Materials, LLC | Eliminations
Current assets:
Cash and cash equivalents	(3,641)	(6,477)
Accounts receivable, net	109	(33)
Intercompany receivables	(1,707,752)	(1,385,708)
Costs and estimated earnings in excess of billings	0	0
Inventories	0	0
Other current assets	0	0
Total current assets	(1,711,284)	(1,392,218)
Property, plant and equipment including finance lease right-of-use assets, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Operating lease right-of-use assets	0	0
Other assets	(4,175,921)	(3,709,690)
Total assets	(5,887,205)	(5,101,908)
Current liabilities:
Current portion of debt	0	0
Current portion of acquisition-related liabilities	0	0
Accounts payable	109	(33)
Accrued expenses	(3,641)	(6,477)
Current operating lease liabilities	0	0
Intercompany payables	(1,707,752)	(1,385,708)
Billings in excess of costs and estimated earnings	0	0
Total current liabilities	(1,711,284)	(1,392,218)
Long-term debt	0	0
Acquisition-related liabilities	0	0
Noncurrent operating lease liabilities	0	0
Other noncurrent liabilities	(164,421)	(137,018)
Total liabilities	(1,875,705)	(1,529,236)
Total member's interest	(4,011,500)	(3,572,672)
Total liabilities and stockholders' equity / member's interest	(5,887,205)	(5,101,908)
Issuers | Summit Materials, LLC | Reportable Legal Entities
Current assets:
Cash and cash equivalents	401,074	302,474
Accounts receivable, net	4	0
Intercompany receivables	404,459	443,323
Costs and estimated earnings in excess of billings	0	0
Inventories	0	0
Other current assets	2,840	1,763
Total current assets	808,377	747,560
Property, plant and equipment including finance lease right-of-use assets, net	9,410	11,602
Goodwill	0	0
Intangible assets, net	0	0
Operating lease right-of-use assets	2,615	3,316
Other assets	4,022,729	3,596,161
Total assets	4,843,131	4,358,639
Current liabilities:
Current portion of debt	6,354	7,942
Current portion of acquisition-related liabilities	0	0
Accounts payable	3,889	4,588
Accrued expenses	54,108	51,043
Current operating lease liabilities	913	764
Intercompany payables	1,215,043	922,356
Billings in excess of costs and estimated earnings	0	0
Total current liabilities	1,280,307	986,693
Long-term debt	1,892,347	1,851,057
Acquisition-related liabilities	0	0
Noncurrent operating lease liabilities	2,567	3,480
Other noncurrent liabilities	5,142	4,259
Total liabilities	3,180,363	2,845,489
Total member's interest	1,662,768	1,513,150
Total liabilities and stockholders' equity / member's interest	4,843,131	4,358,639
100% Owned Guarantors | Summit Materials, LLC | Reportable Legal Entities
Current assets:
Cash and cash equivalents	10,287	5,488
Accounts receivable, net	230,199	234,053
Intercompany receivables	1,303,293	942,385
Costs and estimated earnings in excess of billings	7,504	12,291
Inventories	193,417	199,794
Other current assets	6,797	10,308
Total current assets	1,751,497	1,404,319
Property, plant and equipment including finance lease right-of-use assets, net	1,746,045	1,674,443
Goodwill	1,142,083	1,142,063
Intangible assets, net	47,852	23,498
Operating lease right-of-use assets	21,880	24,551
Other assets	207,699	168,314
Total assets	4,917,056	4,437,188
Current liabilities:
Current portion of debt	0	0
Current portion of acquisition-related liabilities	7,827	30,200
Accounts payable	108,805	103,812
Accrued expenses	106,320	72,970
Current operating lease liabilities	6,114	6,571
Intercompany payables	485,401	447,827
Billings in excess of costs and estimated earnings	15,508	12,183
Total current liabilities	729,975	673,563
Long-term debt	0	0
Acquisition-related liabilities	12,246	17,666
Noncurrent operating lease liabilities	16,062	18,047
Other noncurrent liabilities	208,540	203,919
Total liabilities	966,823	913,195
Total member's interest	3,950,233	3,523,993
Total liabilities and stockholders' equity / member's interest	4,917,056	4,437,188
Non-Guarantors | Summit Materials, LLC | Reportable Legal Entities
Current assets:
Cash and cash equivalents	10,461	9,834
Accounts receivable, net	24,384	19,236
Intercompany receivables	0	0
Costs and estimated earnings in excess of billings	1,162	797
Inventories	6,891	4,993
Other current assets	1,791	1,760
Total current assets	44,689	36,620
Property, plant and equipment including finance lease right-of-use assets, net	94,714	61,404
Goodwill	60,208	58,636
Intangible assets, net	0	0
Operating lease right-of-use assets	4,048	4,910
Other assets	493	734
Total assets	204,152	162,304
Current liabilities:
Current portion of debt	0	0
Current portion of acquisition-related liabilities	0	0
Accounts payable	8,619	8,603
Accrued expenses	4,014	2,701
Current operating lease liabilities	1,161	1,092
Intercompany payables	7,308	15,525
Billings in excess of costs and estimated earnings	991	1,681
Total current liabilities	22,093	29,602
Long-term debt	0	0
Acquisition-related liabilities	0	0
Noncurrent operating lease liabilities	2,871	3,854
Other noncurrent liabilities	117,921	80,169
Total liabilities	142,885	113,625
Total member's interest	61,267	48,679
Total liabilities and stockholders' equity / member's interest	$ 204,152	$ 162,304

Senior Notes' Guarantor and N_4

Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Condensed Financial Statements, Captions [Line Items]
Revenue	$ 2,332,451	$ 2,222,140	$ 2,101,002
Cost of revenue	1,583,996	1,526,332	1,475,779
Depreciation, depletion, amortization and accretion	221,320	217,102	204,910
Operating income	225,173	213,558	162,466
Gain on sale of business	0	0	(12,108)
Income from operations before taxes	129,055	78,224	96,077
Income tax expense (benefit)	(12,185)	17,101	59,747
Net income attributable to Summit Inc.	137,967	59,066	33,906
Comprehensive income (loss) income attributable to member of Summit Materials, LLC	139,722	59,833	29,201
Summit Materials, LLC
Condensed Financial Statements, Captions [Line Items]
Revenue	2,332,451	2,222,140	2,101,002
Cost of revenue	1,583,996	1,526,332	1,475,779
General and administrative expenses	301,962	265,148	257,847
Depreciation, depletion, amortization and accretion	221,320	217,102	204,910
Operating income	225,173	213,558	162,466
Other (income) loss, net	82	2,588	(15,367)
Interest expense (income)	103,291	115,988	115,831
Gain on sale of business	0	0	(12,108)
Income from operations before taxes	121,800	94,982	74,110
Income tax expense (benefit)	1,063	6,385	10,273
Net income attributable to Summit Inc.	120,737	88,597	63,837
Comprehensive income (loss) income attributable to member of Summit Materials, LLC	123,125	91,242	57,356
Summit Materials, LLC | Eliminations
Condensed Financial Statements, Captions [Line Items]
Revenue	(17,166)	(12,196)	(6,084)
Cost of revenue	(17,166)	(12,196)	(6,084)
General and administrative expenses	0	0	0
Depreciation, depletion, amortization and accretion	0	0	0
Operating income	0	0	0
Other (income) loss, net	331,667	291,662	247,657
Interest expense (income)	0	0	0
Gain on sale of business			0
Income from operations before taxes	(331,667)	(291,662)	(247,657)
Income tax expense (benefit)	0	0	0
Net income attributable to Summit Inc.	(331,667)	(291,662)	(247,657)
Comprehensive income (loss) income attributable to member of Summit Materials, LLC	(329,279)	(289,017)	(254,138)
Summit Materials, LLC | Issuers | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Revenue	0	0	0
Cost of revenue	0	0	0
General and administrative expenses	72,504	58,099	62,376
Depreciation, depletion, amortization and accretion	3,983	3,997	2,622
Operating income	(76,487)	(62,096)	(64,998)
Other (income) loss, net	(328,914)	(279,517)	(249,204)
Interest expense (income)	130,176	127,734	118,857
Gain on sale of business			0
Income from operations before taxes	122,251	89,687	65,349
Income tax expense (benefit)	1,514	1,090	1,512
Net income attributable to Summit Inc.	120,737	88,597	63,837
Comprehensive income (loss) income attributable to member of Summit Materials, LLC	123,125	91,242	57,356
Summit Materials, LLC | 100% Owned Guarantors | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Revenue	2,259,865	2,139,457	2,018,428
Cost of revenue	1,542,586	1,473,124	1,416,222
General and administrative expenses	217,897	195,683	184,917
Depreciation, depletion, amortization and accretion	210,038	207,277	197,406
Operating income	289,344	263,373	219,883
Other (income) loss, net	(2,473)	(8,767)	(14,643)
Interest expense (income)	(31,402)	(16,561)	(7,818)
Gain on sale of business			(12,108)
Income from operations before taxes	323,219	288,701	254,452
Income tax expense (benefit)	(4,737)	3,377	8,226
Net income attributable to Summit Inc.	327,956	285,324	246,226
Comprehensive income (loss) income attributable to member of Summit Materials, LLC	330,185	287,395	243,359
Summit Materials, LLC | Non-Guarantors | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Revenue	89,752	94,879	88,658
Cost of revenue	58,576	65,404	65,641
General and administrative expenses	11,561	11,366	10,554
Depreciation, depletion, amortization and accretion	7,299	5,828	4,882
Operating income	12,316	12,281	7,581
Other (income) loss, net	(198)	(790)	823
Interest expense (income)	4,517	4,815	4,792
Gain on sale of business			0
Income from operations before taxes	7,997	8,256	1,966
Income tax expense (benefit)	4,286	1,918	535
Net income attributable to Summit Inc.	3,711	6,338	1,431
Comprehensive income (loss) income attributable to member of Summit Materials, LLC	$ (906)	$ 1,622	$ 10,779

Senior Notes' Guarantor and N_5

Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	$ 408,869	$ 337,184	$ 209,368
Cash flow from investing activities:
Acquisitions, net of cash acquired	(123,477)	(5,392)	(246,017)
Purchase of property, plant and equipment	(177,249)	(177,495)	(220,685)
Proceeds from the sale of property, plant, and equipment	14,018	21,173	21,635
Proceeds from sale of business	0	0	21,564
Other	1,121	(1,095)	3,804
Net cash used for investing activities	(285,587)	(162,809)	(419,699)
Cash flow from financing activities:
Net proceeds from debt issuance	700,000	300,000	64,500
Payments on long-term debt	(674,045)	(270,229)	(85,042)
Payments on acquisition-related liabilities	(33,257)	(33,883)	(36,504)
Debt issuance costs	(9,605)	(6,312)	(550)
Distributions from partnership	0	0	(69)
Other	(907)	(502)	(1,943)
Net cash (used in) provided by financing activities	(16,771)	8,150	(43,993)
Impact of foreign currency on cash	351	286	(724)
Net increase in cash	106,862	182,811	(255,048)
Cash and cash equivalents—beginning of period	311,319	128,508	383,556
Cash and cash equivalents—end of period	418,181	311,319	128,508
Summit Materials, LLC
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	408,869	337,184	209,368
Cash flow from investing activities:
Acquisitions, net of cash acquired	(123,477)	(5,392)	(246,017)
Purchase of property, plant and equipment	(177,249)	(177,495)	(220,685)
Proceeds from the sale of property, plant, and equipment	14,018	21,173	21,635
Proceeds from sale of business	0	0	21,564
Other	1,121	(1,095)	3,804
Net cash used for investing activities	(285,587)	(162,809)	(419,699)
Cash flow from financing activities:
Proceeds from investment by member	1,043	19,076	15,615
Net proceeds from debt issuance	700,000	300,000	64,500
Loans received from and payments made on loans from other Summit Companies	0	0	0
Payments on long-term debt	(674,045)	(270,229)	(85,042)
Payments on acquisition-related liabilities	(30,757)	(31,383)	(34,004)
Debt issuance costs	(9,605)	(6,312)	(550)
Distributions from partnership	(2,500)	(2,500)	(2,569)
Other	(907)	(502)	(1,943)
Net cash (used in) provided by financing activities	(16,771)	8,150	(43,993)
Impact of foreign currency on cash	351	286	(724)
Net increase in cash	106,862	182,811	(255,048)
Cash and cash equivalents—beginning of period	311,319	128,508	383,556
Cash and cash equivalents—end of period	418,181	311,319	128,508
Summit Materials, LLC | Eliminations
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	0	0	0
Cash flow from investing activities:
Acquisitions, net of cash acquired	0	0	0
Purchase of property, plant and equipment	0	0	0
Proceeds from the sale of property, plant, and equipment	0	0	0
Proceeds from sale of business			0
Other	0	0	0
Net cash used for investing activities	0	0	0
Cash flow from financing activities:
Proceeds from investment by member	0	0	0
Net proceeds from debt issuance	0	0	0
Loans received from and payments made on loans from other Summit Companies	2,836	(1,607)	7,502
Payments on long-term debt	0	0	0
Payments on acquisition-related liabilities	0	0	0
Debt issuance costs	0	0	0
Distributions from partnership	0	0	0
Other	0	0	0
Net cash (used in) provided by financing activities	2,836	(1,607)	7,502
Impact of foreign currency on cash	0	0	0
Net increase in cash	2,836	(1,607)	7,502
Cash and cash equivalents—beginning of period	(6,477)	(4,870)	(12,372)
Cash and cash equivalents—end of period	(3,641)	(6,477)	(4,870)
Issuers | Summit Materials, LLC | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	(135,895)	(112,019)	(142,315)
Cash flow from investing activities:
Acquisitions, net of cash acquired	0	0	0
Purchase of property, plant and equipment	(2,150)	(2,513)	(7,607)
Proceeds from the sale of property, plant, and equipment	0	0	0
Proceeds from sale of business			0
Other	0	0	0
Net cash used for investing activities	(2,150)	(2,513)	(7,607)
Cash flow from financing activities:
Proceeds from investment by member	(91,142)	(21,614)	(146,533)
Net proceeds from debt issuance	700,000	300,000	64,500
Loans received from and payments made on loans from other Summit Companies	298,656	287,029	51,696
Payments on long-term debt	(657,942)	(256,354)	(69,265)
Payments on acquisition-related liabilities	0	0	0
Debt issuance costs	(9,605)	(6,312)	(550)
Distributions from partnership	(2,500)	(2,500)	(2,569)
Other	(822)	(462)	(879)
Net cash (used in) provided by financing activities	236,645	299,787	(103,600)
Impact of foreign currency on cash	0	0	0
Net increase in cash	98,600	185,255	(253,522)
Cash and cash equivalents—beginning of period	302,474	117,219	370,741
Cash and cash equivalents—end of period	401,074	302,474	117,219
100% Owned Guarantors | Summit Materials, LLC | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	502,595	431,323	340,401
Cash flow from investing activities:
Acquisitions, net of cash acquired	(92,085)	(5,392)	(246,017)
Purchase of property, plant and equipment	(173,228)	(163,652)	(188,435)
Proceeds from the sale of property, plant, and equipment	13,935	21,083	21,263
Proceeds from sale of business			21,564
Other	1,121	(1,095)	3,804
Net cash used for investing activities	(250,257)	(149,056)	(387,821)
Cash flow from financing activities:
Proceeds from investment by member	87,925	40,690	162,148
Net proceeds from debt issuance	0	0	0
Loans received from and payments made on loans from other Summit Companies	(288,711)	(280,836)	(65,845)
Payments on long-term debt	(15,911)	(13,650)	(15,662)
Payments on acquisition-related liabilities	(30,757)	(31,383)	(34,004)
Debt issuance costs	0	0	0
Distributions from partnership	0	0	0
Other	(85)	(40)	(1,031)
Net cash (used in) provided by financing activities	(247,539)	(285,219)	45,606
Impact of foreign currency on cash	0	0	0
Net increase in cash	4,799	(2,952)	(1,814)
Cash and cash equivalents—beginning of period	5,488	8,440	10,254
Cash and cash equivalents—end of period	10,287	5,488	8,440
Non-Guarantors | Summit Materials, LLC | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	42,169	17,880	11,282
Cash flow from investing activities:
Acquisitions, net of cash acquired	(31,392)	0	0
Purchase of property, plant and equipment	(1,871)	(11,330)	(24,643)
Proceeds from the sale of property, plant, and equipment	83	90	372
Proceeds from sale of business			0
Other	0	0	0
Net cash used for investing activities	(33,180)	(11,240)	(24,271)
Cash flow from financing activities:
Proceeds from investment by member	4,260	0	0
Net proceeds from debt issuance	0	0	0
Loans received from and payments made on loans from other Summit Companies	(12,781)	(4,586)	6,647
Payments on long-term debt	(192)	(225)	(115)
Payments on acquisition-related liabilities	0	0	0
Debt issuance costs	0	0	0
Distributions from partnership	0	0	0
Other	0	0	(33)
Net cash (used in) provided by financing activities	(8,713)	(4,811)	6,499
Impact of foreign currency on cash	351	286	(724)
Net increase in cash	627	2,115	(7,214)
Cash and cash equivalents—beginning of period	9,834	7,719	14,933
Cash and cash equivalents—end of period	$ 10,461	$ 9,834	$ 7,719

Uncategorized Items - _IXDS

Label	Element	Value
Stock Issued During Period, Value, Stock Options Exercised	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised	$ 1,043,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	28,857,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	0
Other Equity Activity, Value	sum_OtherEquityActivityValue	(1,458,000)
Noncontrolling Interest In Lp [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	3,273,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	(2,230,000)
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	58,000
AOCI Attributable to Parent [Member]
Other Comprehensive Income (Loss), Net of Tax	us-gaap_OtherComprehensiveIncomeLossNetOfTax	1,755,000
Additional Paid-in Capital [Member]
Stock Issued During Period, Value, Stock Options Exercised	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised	1,042,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	28,857,000
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	2,226,000
Other Equity Activity, Value	sum_OtherEquityActivityValue	(1,464,000)
Retained Earnings [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	137,967,000
Common Class A [Member] | Common Stock [Member]
Stock Issued During Period, Value, Stock Options Exercised	us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised	$ 1,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised	54,517
Other Equity Activity, Shares	sum_OtherEquityActivityShares	650,206
Stock Issued During Period, Value, Conversion of Units	us-gaap_StockIssuedDuringPeriodValueConversionOfUnits	$ 4,000
Other Equity Activity, Value	sum_OtherEquityActivityValue	$ 6,000
Stock Issued During Period, Shares, Conversion of Units	us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits	376,487