Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 19, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Foundation Building Materials, Inc.
Entity Central Index Key	0001688941
Trading Symbol	FBM
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock Shares Outstanding (in shares)		42,907,326
Entity Public Float			$ 225.4
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q4
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false