St. Thomas: questions buyers ask
What records explain additional residential units at a St. Thomas home?
Section 4.2.11 of the City's Zoning By-law 50-88 (office consolidation of September 2026) and the City's Additional Residential Units guidebook for 2026.
Sources checked October 29, 2026
The rule in St. Thomas
Up to 4 homes on a lot
St. Thomas zoning by-law 50-88 s.4.2.11: permits up to three additional residential units with a single detached, semi-detached or street townhouse dwelling in any residential zone, all in the house or up to two in the house and one in a rear- or side-yard accessory building; one parking space each; none in a regulated flood plain or in a basement below the sewer level, and full municipal services are required.
From St. Thomas by-law 50-88 s.4.2.11, checked 29 Oct 2026
- The recordAdditional residential units
- Where to read itAdditional Residential Units; Additional Residential Units guidebook 2026 and 2 more
- The free check reads itPick “Extra units allowed”
What the record shows
Section 4.2.11 of Zoning By-law 50-88, as amended by By-laws 59-2023 and 106-2025, permits additional residential units in any residential zone with a single detached, semi-detached or street townhouse dwelling, to a maximum of three per lot beside the primary dwelling: all of them in the house, or up to two in the house and one in an accessory structure in the rear or interior side yard. A unit in an accessory structure in the rear yard is set back at least 1 metre from the interior side and rear lot lines and 4 metres from an exterior side lot line and is at most 4 metres high; each additional unit needs one parking space, which may be in tandem; a 1.0-metre pathway leads from the street to its entrance; and lot coverage may reach 45% where an additional unit is on the lot.
The by-law does not permit an additional unit in a flood plain regulated by the conservation authority having jurisdiction, in a basement whose finished floor is below the level of the sanitary sewer serving the building, or where full municipal water and sanitary services are not available. The City's guidebook says every additional unit needs a building permit, and a change of use permit is required to alter a dwelling to additional units. A general permission does not make an existing basement apartment lawful; the building permit and inspection records are where that is answered.
Where to read it yourself
- Additional Residential Units: the City's page, with the guidebook
- Additional Residential Units guidebook 2026: the City's guide to the zoning rules, permits and the building process (PDF)
- Zoning By-law: the City's zoning page and online zoning map
- Zoning By-law 50-88: the office consolidation of September 2026, section 4.2.11 (PDF)
What OfferDue covers in St. Thomas
Extra units allowed is in the free check as a summary of the City's rule, from our hand-kept table of city rules, and the full report reads the lot's zone where the City's zoning map is open data we can use; where it isn't, the report's line says where the City publishes it. Neither is confirmation that a particular unit holds a permit or may be occupied.
Free check: pick “Extra units allowed” See the sample report
Public-record information, not legal, financial, insurance or inspection advice. Records change and can be incomplete, and this page describes the records, not any particular home. What we cover, city by city.