Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2020
Apr. 09, 2021
Jun. 30, 2020
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-K    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2020    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2020    
Entity Filer Category Non-accelerated Filer    
Entity Incorporation, State or Country Code DE    
Entity Address, State or Province NY    
Entity Address, Address Line One <span style="border-left: none; border-right: none;"><span style="border-left: none; border-right: none;">17</span> State Street</span>,    
Entity Address, Address Line Two <span style="border-left: none; border-right: none;">19</span>th 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 Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
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 Public Float     $ 22,951,825
Entity Common Stock, Shares Outstanding   8,821,289