A home addition is the most complex and expensive residential renovation — but also one of the most transformative. In 2026, expect to pay $200–$400 per square foot for a main-floor addition in most Canadian cities, with second-story additions running slightly higher. A 400 sqft addition (master bedroom + ensuite) typically costs $100,000–$180,000.
| Category | Cost Range | Notes |
|---|---|---|
| Foundation & Structural | $15,000–$40,000 | New foundation, footings, and framing — the biggest cost. |
| Exterior (siding, roofing, windows) | $15,000–$35,000 | Matching existing exterior is critical for aesthetics. |
| Rough-in (electrical, plumbing, HVAC) | $15,000–$30,000 | All new systems required in addition space. |
| Insulation & Drywall | $8,000–$15,000 | Higher R-values required in newer builds. |
| Interior Finishes | $15,000–$40,000 | Flooring, trim, paint, doors — matching existing home. |
| Permits & Engineering | $3,000–$12,000 | Structural engineer drawings are required. |
| Architectural Design | $5,000–$20,000 | Architect or designer fees — often required by permit office. |
| Landscaping Restoration | $2,000–$8,000 | Restoring yard after excavation and construction. |
Check building permit requirements, fees, and timelines for your specific city across 800+ Canadian municipalities.
View Permit Requirements →A simple bump-out (under 200 sqft) on an existing foundation costs $40,000–$80,000. A full second-story addition can run $150,000–$400,000.
Adding over a crawl space or slab requires different (more expensive) work than a full basement foundation.
Matching brick, siding, roofline, and interior details adds cost but is essential for resale value.
Your municipality's setback rules determine how close to property lines you can build — and whether your addition is even permitted.
Foundations can only be poured above freezing — plan for spring or summer start dates in most Canadian provinces.
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Find Contractors →Yes — without exception. Home additions require building permits, and typically also require drawings stamped by a structural engineer. Expect a 4–12 week permit approval process.
From design to completion, plan for 6–18 months. Design and permitting alone take 2–4 months. Construction typically takes 4–8 months for a standard addition.
In hot Canadian markets where larger homes are scarce, an addition can be very cost-effective — especially if you love your neighbourhood and school zone. Run the numbers: compare addition cost vs. moving costs (real estate fees, land transfer tax, higher mortgage).
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