Short answer: A coach house is a self-contained second home in its own building on the same lot as a main house, usually in the rear yard and often over a garage. Ontario counts it as an additional residential unit: the Government of Ontario says a second unit can be in your house, above a laneway garage or in a coach house. Ottawa and Markham use "coach house" as a defined zoning term; Toronto calls the same idea a laneway or garden suite.
Key takeaways
| Question | Short answer | Source |
|---|---|---|
| What is it? | A self-contained home in its own building on the same lot as the main house | City of Ottawa — How to plan your coach house |
| Legal status in Ontario | A type of additional residential unit; up to three units on eligible urban lots, one may be in an ancillary building | Planning Act s. 16(3), s. 35.1 |
| Markham definition | Most of the unit above a detached rear-yard garage on a lot accessed by a lane; max height 8.0 m, minimum two storeys | City of Markham — Coach Houses and Garden Homes (April 2026) |
| Ottawa | Defined zoning term since 2017; new Zoning By-law 2026-50 enacted March 11, 2026 | Engage Ottawa — By-law 2026-50 |
| Toronto term | Laneway suite (on a public lane) or garden suite (no lane) | City of Toronto — Garden Suites |
| Permit? | Yes, a building permit is required | City of Ottawa |
Coach house meaning and similar terms
The name comes from outbuildings that once stored horse-drawn coaches and carriages, which is why "coach house" and "carriage house" are used interchangeably. Today the term means a small, self-contained home with its own kitchen, bathroom and sleeping area, detached from the main house and often built over or beside a garage. Ontario's laneway house guide notes that additional residential units go by many names, including second or basement suites, accessory dwelling units, secondary detached dwelling units, granny flats, coach houses, tiny homes and laneway suites, and that municipal zoning by-laws decide which of these count.
| Term | Where you will see it | What it usually means |
|---|---|---|
| Coach house / carriage house | Ottawa and Markham zoning; everyday use | Detached unit in its own building, often over a garage |
| Garden suite / garden home | Toronto (garden suite), Markham (garden home) | Detached rear-yard unit on a lot without a lane |
| Laneway suite / laneway house | Toronto and other cities with public lanes | Detached unit next to a public lane |
| Additional residential unit (ARU) | Ontario Planning Act | The legal umbrella term for all of the above |
New to the umbrella term? Read what is an ADU.
What Ontario allows
The Planning Act (s. 16(3) and s. 35.1) stops official plans and zoning by-laws from prohibiting up to three residential units on a parcel of urban residential land, one of which can be in an ancillary building such as a coach house. That sets a floor, not a design: your city's zoning still controls height, setbacks, lot coverage and parking, and you still need a building permit. Compare local rules in our GTA garden suite rules comparison.
Coach houses in Ottawa
Ottawa changed its zoning by-law in 2017 to permit coach houses, according to Ontario's laneway house guide. The City's coach house guide defines a coach house as a separate dwelling unit that is subsidiary to and on the same lot as a principal dwelling unit but is contained in its own building. In the urban area it must sit in the rear yard; on a lot that fronts both a street and a travelled public lane, it goes in the yard next to the lane. It cannot be severed from the main lot, and a building permit is required in all circumstances.
Ottawa Council enacted a new Zoning By-law 2026-50 on March 11, 2026 (Engage Ottawa), so confirm the current coach house size, height and setback rules with the City before you design.
Coach houses in Markham
Markham's Coach Houses and Garden Homes guide (April 2026, based on Zoning By-law 2024-19 and the 2024 Ontario Building Code) sets out these coach house site requirements:
- Definition: a dwelling unit where most of the unit is above a detached garage in the rear yard of a property accessed by a lane.
- Setbacks: in the rear yard, at least 4.0 metres from the main building and 1.2 metres from the interior side and rear lot lines (reducible to 0.5 metres on lots under 4,000 square metres with no doors or windows facing that line).
- Height: a maximum of 8.0 metres, with a minimum of two storeys.
- Parking: one space for the main dwelling and one for the coach house; public streets and lanes cannot count as parking.
- One or the other: a property cannot have both a coach house and a garden home.
- Registration: every coach house must be registered with Markham Fire and Emergency Services, and the City charges a fee for that inspection and registration.
Toronto: laneway and garden suites
Toronto's zoning does not use the term coach house. If your lot abuts a public lane, the equivalent is a laneway suite; if it does not, it is a garden suite. The City of Toronto allows one garden suite per property in most residential zones, says utilities are intended to connect from the main house, allows existing garages built with a permit to be converted, and does not permit severing a garden suite onto its own lot. For a side-by-side view, see garden suite vs laneway suite and what a laneway house is.
Can a coach house be modular?
Yes, if it meets zoning and the Building Code. The Government of Ontario notes that a modular home still needs a municipal building permit and must meet the Building Code, the same as a site-built home. A unit over a garage needs structural design for the garage below, so a ground-level detached unit is often the simpler fit for factory-built modules. Modular X builds detached garden and laneway suites in modules; read prefab and modular garden suites in Ontario, see the garden suites hub or browse the guides hub. Every project starts with a free feasibility check of zoning, access, trees and servicing.
FAQs
Sources
- Government of Ontario — Add a second unit in your house
- Planning Act, R.S.O. 1990, c. P.13, s. 16(3) and s. 35.1
- Government of Ontario — Building a laneway house (2021)
- Government of Ontario — Building a modular house
- City of Ottawa — How to plan your coach house in Ottawa
- Engage Ottawa — City Council enacts new Zoning By-law 2026-50
- City of Markham — Coach Houses and Garden Homes: Guide for Homeowners (April 2026)
- City of Toronto — Garden Suites
Disclaimer: Figures cited are market estimates provided for information only and are not a quote. Municipal rules, fees, and programs change — always verify current requirements with your local authority. Modular X provides exact pricing only after a site-specific feasibility review.