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Unlike a shed, a garage is almost always a permit project. Municipal rules decide where it can go, how big and tall it can be and how much of the lot it may cover, and the building code sets requirements for the foundation, the structure and, in an attached garage, the separation that keeps exhaust fumes out of the house. In Canada's climate, the slab and footings also need protection from frost.
This page covers garage types and carports, permits and zoning, foundations, attached-garage safety, doors and wiring, and heating.
Detached vs attached garages, and single vs double
The first choice is whether the garage stands apart from the house or joins it. Size comes next: a single garage fits one vehicle and some storage, while a double gives room for two, or for one car and a workshop, but uses more of the lot and draws more attention from zoning.
- Detached garage: set away from the house, often at the end of the driveway or on a lane, it keeps vehicle fumes out of the living space by design, but you walk outside to reach it.
- Attached garage: sheltered, direct access from the house, but the shared wall and the door into the house must meet building code requirements against fumes.
- Single garage: a smaller footprint that suits narrow lots, and it can be built deeper or with a wider door for storage.
- Double garage: room for two vehicles or a car and a workbench, with a longer roof span and a wide door header that call for heavier framing.
- Carport: a roof on posts, open on the sides, that keeps snow and ice off the car without the walls, door or enclosed slab of a garage; Toronto lists carports among accessory structures that need a permit when larger than 10 m².
Garage permits, zoning, setbacks and lot coverage
A garage brings every land-use rule into play: distance from the lot lines and the street, height, which yard it may occupy, how much of the lot all buildings together may cover, and sometimes how a new driveway meets the street. Each municipality sets these rules, and they can differ from one neighbourhood to the next, so the first call is to your municipality's permit or planning office, before paying for a design.
Toronto's permit guidance, for example, requires a building permit for an accessory structure larger than 10 m², naming detached garages and carports, and for any accessory structure attached to an existing building or with plumbing, whatever its size; the zoning bylaw applies even where no permit is needed. Montreal lists detached garages among the outbuildings on its page on sheds and other outbuildings, with the permit depending on the type or dimensions and each borough setting the maximum height and the required distances.
- A survey or, in Quebec, a certificate of location shows the lot lines, existing buildings and any easements the garage must avoid.
- Lot coverage counts the house, the garage and other outbuildings together, which can limit a double garage on a small lot.
- Plan where roof water from a large garage will go, so it stays on your lot and away from foundations.
How a garage is built: slab on grade, frost protection and structure
Most garages sit on a concrete slab on grade: a floor poured over compacted granular fill, with thickened edges or foundation walls that carry the walls and are protected from frost. Whether that protection comes from footings below the frost line or from an insulated shallow foundation depends on the soil, the design and what the local building department accepts. The floor is sloped toward the door or a drain so meltwater from the car runs out.
Some projects need an engineer and others benefit from one: a large span, a long door header, a room above, a sloped lot, poor soil or a garage built against an existing foundation may call for a structural engineer's design, as the structural engineers page explains. In Quebec, the contractor must hold a licence from the Régie du bâtiment du Québec for the work, and you can check a contractor's licence on the RBQ's website.
- Survey, design and permit application, with drawings the municipality can review.
- Utility locates and excavation, then forms, reinforcement and the concrete foundation or slab.
- Wall and roof framing, sheathing, roofing, windows and the door opening.
- Electrical rough-in and any heating, inspected before the walls are closed.
- Siding, trim, the overhead door and the municipality's final inspection.
Attached garage safety: a gas-tight separation and a self-closing door
An attached garage holds cars, fuel and fumes right next to living space, so the building code treats the shared wall and door directly. In the National Building Code, as reproduced in provincial codes, Article 9.10.9.16 calls for an air barrier system between an attached garage and the rest of the building that provides an effective barrier to gas and exhaust fumes, and requires every door between them to meet Article 9.10.13.15. That article requires the door to be tight-fitting and weather-stripped against gas and exhaust fumes and to have a self-closing device, and it doesn't allow the doorway to be in a room intended for sleeping. Your province's code and the municipal inspector confirm what applies to your project.
- Seal every opening in the shared wall and ceiling, including wiring, pipes, ducts and any attic hatch.
- If there is a room over the garage, the floor between them is part of the same barrier.
- Never prop the door open or remove its closer; a door that no longer latches and seals needs repair, as the door repair page explains.
- A carbon monoxide alarm in the house adds protection; ask your municipality which rules apply where you live.
Garage doors, wiring and EV charger rough-in
The overhead door, the electrical service and a future EV charger are easiest to get right when they're planned with the framing. Door size sets the header and the wall layout, and wiring has to be in before insulation and drywall.
- Garage doors: settle the width, height, insulation and windows before framing; the garage doors and garage door openers pages cover choosing and installing them.
- Electrical: lighting, outlets and often a dedicated circuit or subpanel, installed by a licensed electrician; in Ontario the work is reported to the Electrical Safety Authority, and in Quebec electrical contractors are qualified through the Corporation des maîtres électriciens du Québec.
- EV charger rough-in: even before you own an electric vehicle, have the electrician plan the capacity and run conduit or cable to where a charger would go; the EV charger installation page covers the charger itself.
- Detached garages: power arrives by an underground line from the house, which has to be located, trenched and inspected before it's buried.
Insulating and heating a garage for Canadian winters
An unheated garage keeps snow off the car and stays warmer than outdoors, especially when attached. Insulating the walls, ceiling and door makes it usable as a winter workshop and reduces heat loss through the shared wall of an attached garage. If you plan to heat it, insulation, air sealing and a vapour barrier belong in the design from the start, since a warm garage collects moisture from wet cars and snowmelt.
- Electric heaters need a circuit sized by the electrician, and gas-fired heaters must be installed and vented by a licensed gas fitter.
- Insulation at the slab edge or under the slab helps a heated garage stay warm and limits frost at the perimeter.
- Never run a vehicle or a fuel-burning tool with the door closed, heated or not.
Garage Builders: frequently asked questions
Do I need a permit to build a garage?
Almost always. Toronto requires a building permit for accessory structures such as detached garages larger than 10 m² and for any accessory structure attached to the house, and zoning applies either way. In Montreal, detached garages fall under borough rules on outbuildings. Ask your municipality before designing.
Is a detached or an attached garage better?
An attached garage gives sheltered access but needs a fume-tight shared wall and a self-closing door into the house. A detached garage keeps fumes away from the house and can suit a lane or a deep lot, but you walk outside to reach it. Zoning often narrows the choice.
Does a garage need a structural engineer?
Not always. Many simple garages can be built to the building code's standard requirements, but a large span, a room above, poor soil or a sloped lot may call for an engineer's design. Your builder or the permit office will tell you when one is required.
Should I rough in an EV charger when building a garage?
It's worth planning now. Having the electrician allow for the capacity and run conduit or cable during construction is simpler than opening finished walls later. The charger itself is covered on the EV charger installation page.
Why must the door from the garage to the house close by itself?
The building code requires a tight-fitting, weather-stripped door with a self-closing device between an attached garage and the house, to keep gas and exhaust fumes out. A door propped open or with a broken closer defeats that protection.
Sources
- When do I need a building permit? — City of Toronto
- Sheds and other outbuildings — Ville de Montréal
- British Columbia Building Code 2018, Division B, Section 9.10: Fire Protection (Articles 9.10.9.16 and 9.10.13.15) — Province of British Columbia
- Notifications and inspections — Electrical Safety Authority
- A licence is mandatory — Corporation des maîtres électriciens du Québec
- Work requiring a licence — Régie du bâtiment du Québec
- Check a contractor's licence — Régie du bâtiment du Québec
Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides