Cover - shares	3 Months Ended
	Apr. 03, 2021	May 04, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Apr. 03, 2021
Document Transition Report	false
Entity File Number	1-14315
Entity Registrant Name	Cornerstone Building Brands, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0127701
Entity Address, Address Line One	5020 Weston Parkway
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	Cary
Entity Address, State or Province	NC
Entity Address, Postal Zip Code	27513
City Area Code	866
Local Phone Number	419-0042
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock $0.01 par value per share
Trading Symbol	CNR
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		125,708,451
Entity Central Index Key	0000883902
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false