Quarterly report pursuant to Section 13 or 15(d)


Cover - shares
9 Months Ended
Sep. 25, 2021
Nov. 05, 2021
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 25, 2021  
Document Fiscal Year Focus 2021  
Entity Registrant Name Janus International Group, Inc.  
Entity Central Index Key 0001839839  
Document Quarterly Report true  
Document Transition Report false  
Document Fiscal Period Focus Q3  
Current Fiscal Year End Date --12-26  
Entity Incorporation, State or Country Code DE  
Entity Address, State or Province GA  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity File Number 001-40456  
Entity Tax Identification Number 86-1476200  
Entity Address, Address Line One 135 Janus International Blvd  
Entity Address, City or Town Temple  
Entity Address, Postal Zip Code 30179  
City Area Code 866  
Local Phone Number 562-2580  
Entity Common Stock, Shares Outstanding   142,936,580
Common Stock [Member]    
Document Information [Line Items]    
Trading Symbol JBI  
Title of 12(b) Security Common Stock, par value $0.0001 per share  
Security Exchange Name NYSE  
Warrant [Member]    
Document Information [Line Items]    
Trading Symbol JBI WS  
Title of 12(b) Security Warrants, each to purchase one share of Common Stock  
Security Exchange Name NYSE