St. Marys zoning for small homes
Town of St. Marys, a single-tier municipality. Population 7,386 (2021 census).
Backyard suite
A separate home in the yard of a house: garden suite, laneway suite or coach house, including prefab, modular or container units used this way.
Allowed with limits · St. Marys’s term: “accessory apartment (in an accessory building)”
One accessory apartment may be placed in an accessory building on a lot with an existing single-detached, semi-detached or townhouse dwelling, instead of inside the house, on lots with municipal water and sewer. Ontario's Planning Act (s. 35.1) overrides zoning provisions that would prohibit one unit in a building ancillary to a house on serviced urban land. [1]
- Maximum size
- Not more than 45% of the main building's gross floor area (including the apartment) and not more than 100 m² (1,076 ft²) (s.5.01.1 a) [2]
- Number allowed
- One accessory apartment per dwelling, either in the dwelling or in an accessory building (s.5.01.1, 5.01.2) [2]
- Setbacks
- Accessory building must meet the main building's front, rear, interior side and exterior side yard requirements for the zone (s.5.01.2 b) [2]
- Maximum height
- Accessory buildings max 4.5 m or the height of the main building, whichever is less (s.5.1.4) [2]
- Separation from house
- At least 1.0 m from the main building (s.5.1.3 c) [2]
- Servicing
- Lot must be serviced by municipal water and sanitary sewer (s.5.01.1 d) [2]
- Where allowed
- Prohibited on lots with a garden suite, and new units prohibited east of the CNR tracks and north of Trout Creek until a secondary access exists (s.5.01.1 c, e) [2]
Ontario-wide rule
Ontario law stops municipalities from banning one residential unit in a building ancillary to a detached house, semi-detached house or rowhouse on a parcel of urban residential land, as long as the lot has no more than three units in total. Municipalities still set most other zoning rules, but provincial law limits parking requirements, minimum unit size, lot coverage and separation distances. These units are also exempt from development charges and parkland dedication. [1][3][4]
Tiny home on a foundation
A small house as the main home on its own lot. The key rule is any minimum dwelling size.
Allowed with limits · St. Marys’s term: “single-detached dwelling”
The main low-density residential zones set a minimum gross floor area of 125 m² (R1) and 100 m² (R2).
- Minimum dwelling size
- 125.0 m² in R1; 100.0 m² in R2 (Table 8B) [2]
Ontario-wide rule
Ontario law sets no minimum total size for a house that is the main dwelling. The Building Code sets minimum room areas, so the smallest compliant dwelling is roughly 17.5 m² by the Province's own estimate. Municipalities may still set minimum floor areas for main dwellings in their zoning by-laws. The provincial ban on minimum sizes covers only additional residential units. [1][5][6][7][8][9][10]
Tiny home on wheels or park model
Living full-time in a tiny home on wheels or a park model home.
Not allowed · St. Marys’s term: “mobile home / travel trailer”
Locating or using a mobile home is prohibited in every zone unless specifically permitted, and mobile home parks and trailer camps are prohibited uses; recreational vehicles may only be parked as an accessory use in residential zones.
- Where allowed
- Mobile homes prohibited in any zone, temporarily or permanently, unless specifically permitted (s.5.13); mobile home parks and trailer camps are prohibited uses (s.5.26) [2]
- Temporary garden suite
- Garden suite is defined (s.3.47.7); one site-specific temporary garden suite (double-wide mobile home, max 140 m²) was authorized by By-law Z48-2004 in the A1-2-T zone (s.6.8.2) [2]
Ontario-wide rule
Ontario has no single rule for living full-time in a tiny home on wheels. A unit on wheels can count as a 'building' that needs a permit and must meet the Building Code once it stays in one place, is hooked up to services or is anchored. Park model trailers are recognized only as seasonal recreational buildings. Municipalities may allow a portable garden suite under a temporary-use by-law for up to 20 years, with extensions of up to 3 years each. [10][5][1][7][6]
Bunkie or sleeping cabin
A small sleeping building with no kitchen, usually beside a cottage or house.
Not allowed · St. Marys’s term: “accessory building”
Accessory buildings may not be used for human habitation except as specifically permitted, and the by-law has no bunkie or sleeping-cabin provision.
- Where allowed
- Accessory uses exclude any building or structure used for human habitation except as specifically permitted (s.5.1.1 b) [2]
Ontario-wide rule
Ontario law has no rule written specifically for bunkies or sleeping cabins. Whether one needs a building permit depends on the Building Code Act's definition of 'building' and the Code's shed exemption. That exemption covers only storage-use sheds, so it does not cover a structure used for sleeping. Municipal zoning rules for accessory buildings still apply. [7][5][1][11]
Official links
Last confirmed October 2026.
Notes and caveats
Sources
- Planning Act (Ontario e-Laws)
- Zoning By-law Z1-1997
- O. Reg. 299/19: Additional residential units (Ontario e-Laws)
- Development Charges Act, 1997 (Ontario e-Laws)
- Government of Ontario PDF
- Build or buy a tiny home: Building Code requirements (Government of Ontario)
- Building Code Act, 1992 (Ontario e-Laws)
- O. Reg. 163/24: Ontario Building Code (Ontario e-Laws)
- 2024 Ontario Building Code (Government of Ontario)
- Build or buy a tiny home: permits and inspections (Government of Ontario)
- Building Code updates (Government of Ontario)
Not legal advice
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