Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
3 Months Ended
Mar. 31, 2021
May 12, 2021
Document and Entity Information [Abstract]    
Entity Registrant Name SG BLOCKS, INC.  
Entity Central Index Key 0001023994  
Trading Symbol SGBX  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Mar. 31, 2021  
Document Fiscal Period Focus Q1  
Document Fiscal Year Focus 2021  
Entity Filer Category Non-accelerated Filer  
Entity Incorporation, State or Country Code DE  
Entity Address, State or Province NY  
Entity Address, Address Line One 17 State Street,  
Entity Address, Address Line Two 19th Floor,  
Entity Address, City or Town New York  
Entity Address, Postal Zip Code 10004  
City Area Code (646)  
Local Phone Number 240-4235  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Security Exchange Name NASDAQ  
Entity Interactive Data Current Yes  
Entity Current Reporting Status Yes  
Entity File Number 001-38037  
Entity Tax Identification Number 95-4463937  
Entity Shell Company false  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   8,822,489