| Cover | Aug. 18, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 18, 2021 |
| Entity File Number | 001-38037 |
| Entity Registrant Name | SG BLOCKS, INC. |
| Entity Central Index Key | 0001023994 |
| Entity Tax Identification Number | 95-4463937 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 195 Montague Street |
| Entity Address, Address Line Two | 14th Floor |
| Entity Address, City or Town | Brooklyn |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 11201 |
| City Area Code | 646 |
| Local Phone Number | 240-4235 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.01 |
| Trading Symbol | SGBX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
