| Cover | Jan. 29, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 29, 2021 |
| Entity Registrant Name | FOUNDATION BUILDING MATERIALS, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38009 |
| Entity Tax Identification Number | 81-4259606 |
| Entity Address, Address Line One | 2520 Red Hill Avenue |
| Entity Address, City or Town | Santa Ana, |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92705 |
| Local Phone Number | 380-3127 |
| City Area Code | 714 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | FBM |
| Security Exchange Name | NYSE |
| Entity Central Index Key | 0001688941 |
| Amendment Flag | false |
| Current Fiscal Year End Date | --12-31 |
