Toronto & GTA home addition costs · Updated October 2026
Home Addition Cost Calculator: Toronto & GTA Prices (2026)
How much does a home addition cost in Toronto? Most additions run about $350–550 per sq ft of construction, before HST. A one-storey rear or side addition is usually $350–450 per sq ft, so 250 sq ft lands around $88,000–113,000. Building a second storey usually costs $400–550 per sq ft, because the house below has to carry it.
Drawings, engineering and permits usually add another 15–25% and are priced from your plans. A simple shape on a slab or crawlspace, standard finishes and no zoning variance keep you near the low end.
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Home addition cost by size (Toronto & GTA, 2026)
Construction cost, standard finishes, before HST and before drawings and permits. Your exact number comes in a fixed, itemized quote.
| Size | One-storey rear or side $350–450 / sq ft | Two-storey rear $350–500 / sq ft | Second storey on top $400–550 / sq ft |
|---|---|---|---|
| 150 sq ft | $53,000–68,000 | — | — |
| 250 sq ft | $88,000–113,000 | $88,000–125,000 | $100,000–138,000 |
| 400 sq ft | $140,000–180,000 | $140,000–200,000 | $160,000–220,000 |
| 600 sq ft | $210,000–270,000 | $210,000–300,000 | $240,000–330,000 |
| 800 sq ft | — | $280,000–400,000 | $320,000–440,000 |
For a two-storey addition, count both floors. A full basement under the addition, a zoning variance or a tight lot are priced only if your project needs them.
What will your addition cost?
Tap 4 answers and see your price range right away. No email needed. Your exact number comes in a fixed, itemized quote with a free 3D design.
What kind of addition?
About how big?
Enter the area of all new floors. A 15 × 20 ft footprint is 300 sq ft on one level, or 600 sq ft over two levels. Drawings confirm the final measurement.
What goes inside?
Optional. Living space and bedrooms are already in the per-sq-ft price.
Which finish level?
Optional: anything we should check?
These do not change your estimate. We check them for free at your visit.
How we got this number
What keeps it near the low end
Only if needed
A cheaper quote is not cheaper if it leaves these out
| With Capable | Check any written quote for |
|---|---|
| Design & 3D renderings included. See the addition on your house first. | Which design views are included before the build, and what stage do they show? |
| One team from foundation to finish, with one fixed, itemized quote | Who coordinates foundation, structure and finishes, and where are exclusions recorded? |
| Lifetime Warranty* | What work, term and transfer rules does the warranty cover? |
| Schedule planning: design → permits → construction → done | Does the quote show the design, permit and construction stages with schedule assumptions? |
What changes the price of a home addition
Out the back or up on top?
A rear or side addition needs a new foundation and roof, and the connection to the house must be designed. A second-storey addition changes the roof and adds a new floor; the plans must show how that floor is supported by the existing walls and foundation, and whether reinforcement is needed. Your lot helps decide which route is possible: setbacks and lot coverage limit how far out you can build, while height limits affect building up. Whether you can stay in the house during construction depends on the actual work.
Feasibility before drawings
Before you pay for full drawings, check what your zoning allows. If the addition needs a minor variance from the Committee of Adjustment, add a few months to the schedule. Our guide before you order addition drawings walks through the checks.
What sits under the addition
A slab or crawlspace is the simplest base. A full basement under the addition gives you more space but usually adds $20,000–50,000 for the deeper foundation and connections.
Soft costs
Architectural drawings, structural engineering, a survey and permits usually add 15–25% on top of construction. They're real costs, so they belong in your budget from day one.
Questions
How long does an addition take? Drawings and permits often take longer than the build itself. You get a full schedule with your quote.
Is it cheaper to build up or out? Per sq ft, building out (one storey at the back) is usually cheaper. If your lot has no room behind, a second storey can still cost less than moving.
Can I add a bathroom or kitchen? Yes. A 3-piece bathroom usually adds $15,000–25,000. A kitchen is priced from your design.
Your addition range still needs a property check.
The number changes if the lot limits where you can build, the existing structure needs reinforcement, or the new foundation and roof must connect to the house in a different way. Keep the calculator result, then share your city, the space you want to add and whether you are considering building out or up. We’ll review what needs checking before drawings and a project-specific quote.
If you are still choosing a direction, read what to check before ordering addition drawings.
Send your current choices and estimate for a scope review.
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