| Document and Entity Information | Oct. 19, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001585389 |
| Document Type | 8-K |
| Document Period End Date | Oct. 19, 2021 |
| Entity Registrant Name | SmartStop Self Storage REIT, Inc. |
| Entity Incorporation State Country Code | MD |
| Entity File Number | 000-55617 |
| Entity Tax Identification Number | 46-1722812 |
| Entity Address, Address Line One | 10 Terrace Road |
| Entity Address, City or Town | Ladera Ranch |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92694 |
| City Area Code | (877) |
| Local Phone Number | 327-3485 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
