St. Thomas zoning for small homes

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 · St. Thomas’s term: “additional residential unit, detached”

One additional residential unit is permitted in an accessory building in the rear or interior side yard of a single detached, semi-detached or street townhouse dwelling in any residential zone, provided full municipal water and sanitary services are available. [1][2]

Maximum height: 4 metres (s.4.2.11.4(c)) [1]
Setbacks: Interior side yard 1 m; exterior side yard 4 m; rear yard 1 m (s.4.2.11.4(c)) [1]
Number allowed: One ARU in an ancillary building, with up to three units in the house, or up to three units in the house with no detached unit (s.4.2.11.2) [1]
Parking: Minimum 1 parking space per ARU; tandem permitted (s.4.2.11.7) [1]
Servicing: Not permitted unless full municipal sanitary and piped water services are available (s.4.2.11.3(d)) [1]
Where allowed: Rear yard or interior side yard only; not in a flood plain regulated by the Conservation Authority (s.4.2.11.3–4.2.11.4) [1]
Minimum lot size: No ARU-specific minimum; maximum lot coverage of 45% where an ARU is on the lot (s.4.2.11.9) [1]

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. [3][4][5]

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. Thomas’s term: “single detached dwelling”

The R1 and R2 zone regulation tables set a minimum ground floor area for single detached dwellings that depends on the number of storeys. [1]

Minimum dwelling size: R1 and R2 zones, single detached dwelling minimum ground floor area: 74 m² (1 storey), 60 m² (1½ storey), 42 m² (2 or more storeys) (Table 1 to s.5.4 item 12; Table to s.6.4 item 12) [1]

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. [3][6][7][8][9][10][11]

Tiny home on wheels or park model

Living full-time in a tiny home on wheels or a park model home.

Not allowed · St. Thomas’s term: “mobile home / trailer”

Section 4.1.10 states that no land in the City shall be used to park, locate or store a motor vehicle, mobile home, motor home or trailer when used as a place for sleeping, living or eating, and no zone permits mobile home or trailer parks. The City's ARU guidebook states that RVs and tiny homes on wheels are not permitted as a detached ARU. [1][2]

Where allowed: Nowhere: s.4.1.10 'Habitation of Vehicles' applies city-wide [1]

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. [11][6][3][8][7]

Bunkie or sleeping cabin

A small sleeping building with no kitchen, usually beside a cottage or house.

Not allowed · St. Thomas’s term: “accessory building”

In residential zones, s.4.2.4.7 states that no accessory building shall be used for human habitation; the only exception is a detached additional residential unit with its own kitchen and bathroom under s.4.2.11. [1]

Maximum height: Accessory buildings: 4 metres (s.4.2.4.8) [1]

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. [8][6][3][12]

Official links

Last confirmed October 2026.

Notes and caveats

The City has no rural or agricultural zones. The ARU Guidebook 2026 lists 'new/revised' detached ARU rules (minimum 2.4 m from another building containing a unit; floor area no more than 50% of the main dwelling) that do not appear in s.4.2.11 of the September 2026 office consolidation, so they may be pending; they are excluded from the facts. The by-law sets no ARU-specific maximum floor area. The general R1 limit on enclosed accessory buildings (lesser of 15% of lot area or 67 m²) may or may not apply to a detached ARU; this is unconfirmed. The s.4.2.4.7 habitation ban on accessory buildings co-exists with the later ARU permission in s.4.2.11.4.

Sources

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St. Thomas zoning for small homes

Backyard suite

Ontario-wide rule

Tiny home on a foundation

Ontario-wide rule

Tiny home on wheels or park model

Ontario-wide rule

Bunkie or sleeping cabin

Ontario-wide rule

Official links

Sources

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