Land, zoning and permits
Coach houses in Ontario: what you can build and what it takes
By Jonathan Kennedy, cabin owner and tiny home rental owner · Last reviewed October 28, 2026
A coach house is a self-contained second home in a separate building on the same lot as a house, often above or beside a garage at the back of the lot. Ontario's Planning Act stops municipalities from banning one on most urban house lots, and it's exempt from development charges, but each town sets its own size, height and setback limits: Markham allows up to 8.0 m with two storeys over a garage on a lane, while Ottawa's long-standing rules cap height at 3.6 m in urban areas.
The garage at the back is falling apart, your parents want to be closer, or the numbers on a rental unit finally make sense. A coach house is one of the few ways to add a home without moving, and Ontario law is now on your side. The catch is in the local details: height, how the water gets there and how a firefighter gets to the door.
What is a coach house?
It's a separate dwelling unit, smaller than and subordinate to the main house, in its own building on the same lot. Markham uses the term for a unit mostly above a detached garage at the rear of a lot on a lane, and calls a unit without a lane a garden home (Markham guide). Ottawa uses it for any detached unit on the lot, which can't be severed (Ottawa coach house guide, 2017). North Dumfries' definition covers a free-standing unit, one above a garage or one in another accessory building (North Dumfries). Toronto calls the same thing a garden or laneway suite.
Can my town say no to a coach house?
Not on most urban house lots. The Planning Act stops a zoning by-law from prohibiting one unit in a building ancillary to a detached, semi-detached or row house on urban residential land, if the house has no more than two units (s. 35.1). The town also can't set a minimum floor area or require more than one parking space for it, and the parts of a by-law that permit it can't be appealed. Anyone can live in it, related or not, and the owner doesn't have to live on the lot (O. Reg. 299/19).
Rural lots are different. In Ottawa, for example, a lot without municipal water and sewer can have only one extra unit, and a rural coach house needs a lot of at least 0.4 hectares unless it's on public or communal services (s. 133).
How big can a coach house be?
It depends on the town. These are the limits from the municipalities we've researched that use the term "coach house" in their by-laws:
| Municipality | Answer | Maximum size |
|---|---|---|
| Milton | Allowed | Accessory building: gross floor area not more than 10% of lot area or 110 m², whichever is less (s.4.2.5 vi); in a detached garage, unit floor area not more than the principal dwelling's floor area or 110 m², whichever is less (s.4.2.2) [source] |
| North Dumfries | Allowed with limits | Lesser of 40% of the footprint of the principal dwelling or 110 m² (1,184 ft²); coach house plus its driveway and parking may not exceed 40% coverage of the rear yard (s.6.40.6-6.40.7) [source] |
| Addington Highlands | Allowed with limits | 45% of the dwelling unit or 100 m², whichever is less (gross floor area) [source] |
| East Ferris | Allowed with limits | No larger in floor area than 75% of the main floor area of the main building (s.3.29.16) [source] |
| Alnwick/Haldimand | Allowed with limits | 50% of the gross floor area of the primary dwelling, or 50 m² where the principal dwelling has a footprint of 100 m² or less (s. 4.30.1 k) [source] |
| Thames Centre | Allowed with limits | In Residential zones, total floor area of all accessory buildings is the lesser of 90 m² or 75% of the dwelling floor area (s.4.1.2) [source] |
| Petawawa | Allowed | Unit area not more than 80% of the primary dwelling's gross floor area; detached footprint not more than 80% of the primary building's footprint (s. 3.32.1(b)(i)) [source] |
| Collingwood | Allowed | No separate floor area cap. The building counts toward the 15% residential lot coverage limit for detached accessory buildings (s.4.33.5, 4.40.2.7). Up to 45% total lot coverage on lots with an ARU (s.4.40) [source] |
| Barrie | Allowed | No floor area cap; counts toward the 10% maximum lot coverage for accessory buildings (s.5.2.9.2(m), 5.3.5(h)); no basement permitted [source] |
| Rule | Markham (By-law 2024-19) | Ottawa (By-law 2008-250) |
|---|---|---|
| Where | Rear yard, accessed by a lane | Rear yard; next to the lane where there is one |
| Height | Up to 8.0 m, at least two storeys | 3.6 m in urban areas (3.2 m flat roof); 4.5 m rural |
| Size | Lot coverage of 15%, or 40 m² on lots under 4,000 m², whichever is greater | Footprint the least of 40% of the house footprint, 40% of the yard, or 80 m² urban (95 m² rural) |
| Setbacks | 4.0 m from the house; 1.2 m from side and rear lines | 1.2 m from other buildings; 1 m or 4 m from lot lines depending on windows and lanes |
| Parking | One space for the coach house | May park in tandem in the house's driveway |
Ottawa brought in a new zoning by-law (2026-50) in March 2026. Where parts of it are still under appeal, the stricter of the old and new rules applies, so confirm Ottawa's current coach house numbers with the City before you design (Ottawa zoning).
How is a coach house connected to water and sewer?
Usually through the main house. In Ottawa's urban areas, a coach house has to be serviced from the principal dwelling, and in rural areas it shares the well and septic system (s. 133). Markham says the water and sewer pipes must be big enough for both buildings' fixtures, and a septic system may need upgrading (Markham guide). Waterloo warns that servicing can be one of the larger costs, and suggests talking to its engineering staff early (Waterloo guide).
Our take: get the servicing quote before the design is final. On an older lot, the run from the street through the house to the back of the yard can cost more than the foundation, and it's the line most first quotes leave out.
What fire access does a coach house need?
A clear path from the street to the door, and the towns that publish numbers set them close to Toronto's. Markham asks for an unobstructed path at least 1.2 m wide, no more than 45 m from the fire truck to the door, and no more than 90 m in total from the hydrant (Markham guide). Ottawa requires a walkway 1.2 to 1.5 m wide from the driveway, street or lane (s. 133). Markham also requires every coach house to be registered with its fire service, which includes a fee-based inspection. The Ontario Fire Code requires access routes to be kept clear of fences, vehicles and vegetation (Fire Code).
Does a coach house pay development charges?
No municipal development charges, in most cases. The Development Charges Act exempts one unit in a building ancillary to a new or existing detached, semi-detached or row house, if the house has no more than two units and no other backyard building has one (Development Charges Act). Waterloo notes that school board (education) development charges can still apply (Waterloo guide).
What does a coach house cost?
A site-built coach house or garden suite costs $180,000 to $400,000 by our 2026 estimate, and a prefab or modular one $150,000 to $300,000 in Ontario before delivery, crane and site work. A coach house over a new garage costs more again, and it needs a fire separation between the garage and the unit. Our cost estimator adds servicing, permits and site work.
Questions people ask
- What's the difference between a coach house and a garden suite?
- Mostly the name. Both are a second home in a separate building on a house lot. Some towns, such as Markham, use coach house for a unit above a garage on a lane and garden home or garden suite for one without a lane.
- Can I rent out a coach house in Ontario?
- Yes. Ontario's rules let anyone live in an additional unit, related to you or not, and the owner doesn't have to live on the lot. Short-term rental rules are separate and set by each municipality.
- How tall can a coach house be in Markham?
- Up to 8.0 m, and it must have at least two storeys, under Zoning By-law 2024-19. It has to be in the rear yard of a lot accessed by a lane.
- Do you need parking for a coach house?
- A municipality can require at most one space for it. Markham requires one; Ottawa lets the coach house car park in tandem in the main driveway.
- Can a coach house be severed and sold?
- Not in Ottawa, where its by-law says a coach house can't be severed from the lot. Elsewhere, selling it separately would need a severance, which is a separate approval.