Cost by size
| Size | Area | Typical total |
|---|---|---|
| 12×20 | 240 sq ft | $14,500–$30,000 |
| 20×20 | 400 sq ft | $24,000–$48,000 |
| 22×24 | 528 sq ft | $31,000–$58,000 |
| 24×30 | 720 sq ft | $40,000–$75,000 |
A second national guide puts a wood-frame structure at $80 to $150 per square foot all in, and a standard single garage with slab and basic electrical at $30,000 to $55,000. The two agree closely enough to plan with.
What the components cost
| Component | Cost |
|---|---|
| Foundation and slab | $4,000–$11,000 |
| Concrete slab, per sq ft | $25–$30 |
| Garage door | $1,200–$4,800 |
| Electrical | $1,200–$5,000 |
| Insulation | $1,500–$5,000 |
| Heating | $1,500–$5,000 |
| Permits | $200–$2,000 |
Attached garages run higher than detached — roughly $40,000 to $70,000 against $30,000 to $60,000 — because tying into the house means matching the roofline, the cladding and the foundation, and because a shared wall has fire separation requirements.
Zoning comes before design
Every Ontario municipality has a zoning by-law that governs accessory structures. Before you draw anything, find out four numbers for your property:
- Maximum ground floor area for an accessory building.
- Maximum height, which is what usually kills the loft idea.
- Setbacks from the rear and side lot lines.
- Lot coverage — the total share of your lot that may be built on, including the house.
People routinely pay for drawings of a garage their lot will not permit. One phone call to the planning department costs nothing and happens before the money starts.
A detached garage always needs a building permit. Our permit guide covers the process, and what happens if you skip it covers why not to.
Slab, frost walls or piers?
This is the structural decision, and it is not a style choice.
- Monolithic or floating slab with thickened, insulated edges: the common Ontario solution, at $25 to $30 per square foot. It resists frost heave by keeping the ground beneath it from freezing.
- Frost walls on footings below the frost line: more expensive, and what a municipality may require for a larger structure or a heated one.
- Piers: for light structures, not usually for a garage holding vehicles.
Your building department decides which is acceptable, and your soil influences it. A quote that does not name the foundation type is not a complete quote.
Power and heat
A detached garage needs a feed from the house, and that is not extension-cord work. It means a trench, buried cable rated for the run, and usually a subpanel in the garage — done by a contractor licensed by the Electrical Safety Authority who files an ESA notification.
If you plan to heat it, decide now rather than later. Insulating during construction is straightforward; insulating a finished garage means opening walls again. And if a workshop, an EV charger or a car lift is anywhere in your plans, size the feed for that today. Pulling a second cable through a trench you already backfilled is the expensive way to save money.
Red flags in a garage quote
| What you see | Why it matters | What to do |
|---|---|---|
| Zoning not checked | Size, height and setbacks are decided by by-law, not by preference | Call your planning department for the four numbers before drawings |
| Foundation type unnamed | Slab, frost walls and piers are different prices and different approvals | Ask which one, and whether the building department has confirmed it |
| Electrical by the framing crew | A buried feed and a subpanel need a licensed electrical contractor and an ESA notification | Ask for the ECRA/ESA licence number of the company doing the wiring |
| Insulation left as “later” | Retrofitting insulation into finished walls costs several times more | Decide heated or unheated before framing starts |
| Permit responsibility unstated | Orders come to the property owner, not the builder | Write into the contract who applies and who books inspections |
| Grading and drainage not discussed | A new roof sheds a lot of water somewhere | Ask where the roof water goes and how the slab is drained |
Frequently asked questions
Height limits in the zoning by-law usually decide the loft, and a dwelling unit above a garage is an additional residential unit with its own rules. Our second unit guide covers what that involves.
Electrical work runs $1,200 to $5,000 depending on the trench length, the cable size and whether a subpanel is installed. It must be done by an ECRA/ESA licensed contractor who files a notification.
Detached, usually: $30,000 to $60,000 against $40,000 to $70,000 attached. An attached garage must match the house structurally and meet fire separation requirements at the shared wall.
Yes. A detached garage needs a building permit everywhere in Ontario, and the size, height and position are governed by your municipal zoning by-law before the permit stage.
At 576 square feet and $90 to $140 per square foot, expect roughly $35,000 to $65,000 for a finished detached structure with a slab, a door and basic power. Heat and insulation add $3,000 to $10,000.
Roughly $90 to $140 per square foot in 2026. A 20×20 runs $24,000 to $48,000, a 22×24 is $31,000 to $58,000 and a 24×30 lands between $40,000 and $75,000 before heating and insulation.
Sources
- Homi Reno, Cost to build a garage, 2026 — homireno.com
- RenoQuotes, Cost to build a detached garage in Canada in 2026, updated 30 April 2026 — renoquotes.com
- Government of Ontario, Your rights when starting home renovations or repairs — ontario.ca, checked 18 September 2026
Prices are published ranges collected on 18 September 2026, not quotes. Zoning rules are municipal — confirm for your own lot.
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