Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 10, 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-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Period Focus	Q3
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	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		8,596,189