How Much Does a Home Addition Cost in Toronto? (2026 Prices)
A home addition in Toronto typically costs $250 to $500 per square foot of new floor area, depending on the addition type (rear, side, second-storey), the finish level, and whether the build requires new foundation work. A typical 300–500 sq ft rear addition in the GTA runs $90,000 to $250,000, while a full second-storey addition on an existing detached home runs $200,000 to $450,000+. Pricing varies meaningfully by city and by the complexity of permits, structural engineering, and integrating new HVAC, electrical, and plumbing with the existing house.
What you'll pay by material
| Material | Cost per sq ft of new floor area | Lifespan | Pros | Cons |
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| Rear Addition (single-storey) | $250 – $400 per sq ft | 50+ years (matches main house) |
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| Side / Side-and-Rear Addition | $280 – $450 per sq ft | 50+ years (matches main house) |
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| Second-Storey Addition | $350 – $500 per sq ft | 50+ years (matches main house) |
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| Garage Conversion or Carport Enclosure | $180 – $280 per sq ft | 50+ years (matches main house) |
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Ranges reflect typical GTA Q1 2026 rates and assume standard access. Every Buildoreno estimate is a free, itemized written quote.
What affects the price?
Every project is different — these are the biggest factors that move your final number.
A 200 sq ft rear addition has a higher per-sq-ft cost than an 800 sq ft addition — small projects don't spread fixed costs (permits, mobilization, engineering) over many square feet. Big additions scale more efficiently.
Builder-grade finishes are at the low end of the range. Custom millwork, premium cabinetry, hardwood floors, quartz counters, and custom tile push every addition $50–$150 per sq ft above base pricing.
Slab-on-grade is cheapest. Full basement under the addition adds $40–$80 per sq ft but gives you the extra floor of space at very low marginal cost. Crawl spaces are a middle ground.
City permit, structural engineer stamp, HVAC design, plumbing permit, and electrical permit — combined typically $5,000–$15,000 depending on city and complexity. Variance applications (when needed) add 4–8 weeks and $2,000–$5,000.
Tying new HVAC, electrical panel, and plumbing into the existing home varies enormously — a newer home with capacity is easy, an older home with knob-and-tube and a 100A panel may need a $15,000–$30,000 service upgrade alongside the addition.
Tight Toronto lots add cost vs. spacious suburban lots. Setbacks, ravine zones, conservation areas, and heritage districts each add review time and design constraints.
What recent homeowners paid
Real examples of what GTA homeowners have paid for similar work.
Single-storey rear addition expanding kitchen. Slab-on-grade foundation, builder-grade finishes, integrated with existing HVAC. 14-week build.
Side addition with full basement underneath. Mid-grade finishes, new electrical sub-panel, exterior brick matched to existing. 18-week build.
Three new bedrooms and two new bathrooms. Includes engineering, permits, full HVAC upgrade, new roof, exterior material matching. 6-month build, family relocates.
Convert existing attached garage to a 400 sq ft office + half-bath. Includes insulation, HVAC tie-in, electrical, and exterior fenestration changes. 10-week build.
Home Addition cost — questions answered
A home addition in Toronto typically costs $250 to $500 per square foot of new floor area, depending on the addition type (rear, side, second-storey), the finish level, and whether the build requires new foundation work. A typical 300–500 sq ft rear addition in the GTA runs $90,000 to $250,000, while a full second-storey addition on an existing detached home runs $200,000 to $450,000+. Pricing varies meaningfully by city and by the complexity of permits, structural engineering, and integrating new HVAC, electrical, and plumbing with the existing house.
Most GTA projects range from $250 – $500 per sq ft of new floor area installed. The exact price depends on material choice, project complexity, and site conditions. We provide detailed written quotes so you know exactly what you are paying for.
Yes. Structural Engineer + Architect Drawings typically runs $5,000 – $15,000 and is commonly overlooked. We include transparent line items in every estimate so there are no surprises on your final invoice.
Yes. Municipal Permit Package typically runs $2,500 – $8,000 and is commonly overlooked. We include transparent line items in every estimate so there are no surprises on your final invoice.
Yes. Variance Application (if needed) typically runs $2,000 – $5,000 and is commonly overlooked. We include transparent line items in every estimate so there are no surprises on your final invoice.
Get your personalized estimate
These are general ranges. For an exact quote based on your home and scope, reach out — no cost, no obligation.