Document and Entity Information - shares	6 Months Ended
	Oct. 31, 2018	Nov. 30, 2018
Document and Entity Information
Entity Registrant Name	GMS Inc.
Entity Central Index Key	0001600438
Document Type	10-Q
Document Period End Date	Oct. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--04-30
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		41,181,834
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2