Document and Entity Information - shares	3 Months Ended
	Jul. 31, 2017	Sep. 06, 2017
Document and Entity Information
Entity Registrant Name	GMS Inc.
Entity Central Index Key	0001600438
Document Type	10-Q
Document Period End Date	Jul. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--04-30
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		40,970,905
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1