| Cover Page | Oct. 23, 2020 |
| Cover [Abstract] | |
| Entity Tax Identification Number | 26-0758017 |
| Entity Ex Transition Period | true |
| Entity File Number | 001-38479 |
| Entity Incorporation, State or Country Code | DE |
| Entity Registrant Name | CONSTRUCTION PARTNERS, INC. |
| Document Period End Date | Oct. 23, 2020 |
| Document Type | 8-K |
| Amendment Flag | false |
| Entity Central Index Key | 0001718227 |
| Entity Emerging Growth Company | true |
| Security Exchange Name | NASDAQ |
| Trading Symbol | ROAD |
| Title of 12(b) Security | Class A common stock, $0.001 par value |
| Pre-commencement Issuer Tender Offer | false |
| Pre-commencement Tender Offer | false |
| Soliciting Material | false |
| Local Phone Number | (334) 673-9763(Registrant’s telephone number, including area code) |
| City Area Code | (334) 673-9763(Registrant’s telephone number, including area code) |
| Written Communications | false |
| Entity Address, Postal Zip Code | 36303 |
| Entity Address, State or Province | AL |
| Entity Address, City or Town | Dothan |
| Entity Address, Address Line One | 290 Healthwest Drive, Suite 2 |
