Home Addition Cost in Canada: Prices by Addition Type

An addition is priced by where the new room sits: on its own foundation beside the house, pushed out a few feet as a bump-out, or on top as a new storey. Ground-floor rooms run about $225 to $550+ a square foot on builders' price guides, and in Toronto that figure leaves out design, permits, HST and contingency, which add a third or more.

Home addition cost per square foot, by type

Additions are priced by type, because a room on a new foundation, a room on top of the house and a small bump-out carry very different fixed costs.

Toronto additions run $350 to $550+ a square foot for a rear or side addition, against $225 to $350 for a main-floor extension in Kitchener-Waterloo. In Toronto the price rises with narrow lot access, heritage rules and the condition of the existing house. For Vancouver, Winnipeg, Saskatoon, Regina and Atlantic Canada, start from these ranges and test them against two or three local quotes.

Rear and side additions

A rear or side addition puts a room on its own foundation beside the house. In Kitchener-Waterloo a 300 sq ft main-floor extension costs $67,500 to $105,000 and a 500 sq ft one $112,500 to $175,000; in Toronto one builder puts a rear addition at $450 to $550 a square foot before HST and soft costs, so 500 sq ft is $225,000 to $275,000 in hard cost. On the same builder's figures that matches a high-quality full-gut renovation in the city at $450 to $550+, so new space and rebuilt space price alike there.

Joining the addition means opening an exterior wall, and where that wall is load-bearing, an engineer sizes the beam that replaces it.

Bump-outs

A bump-out pushes one wall out 4 to 8 feet and costs $40,000 to $80,000 in total on 2026 Kitchener-Waterloo figures. It has the lowest total of any addition and is often the dearest per square foot: a 6 by 12 foot bump-out at $60,000 works out to about $833 a square foot, because the excavation, foundation, roof tie-in and permit are spread over a small area.

Second and third storeys

Second storeys run $350 to $650 a square foot in Toronto on builders' price guides and $250 to $400+ in Kitchener-Waterloo, where 600 sq ft costs $150,000 to $240,000. The house below has to carry the new load, and in Toronto the family typically moves out for 5 to 7 months at $4,000 to $10,000 a month, so a second-storey addition carries a living cost a rear addition does not. A third storey in Toronto runs $550 to $800 a square foot.

Sunrooms and kitchen additions

A four-season sunroom runs $300 to $500+ a square foot in Toronto. A kitchen addition runs $275 to $375 in Kitchener-Waterloo, above the $225 to $350 for a plain main-floor room there, because plumbing, electrical, cabinetry and appliances are concentrated in the new space.

Garage addition permits

The permit for a garage is a small line next to the build: Calgary's 2026 schedule lists $333.84 for a garage and $205.92 for garage renovations and garage additions, and Toronto charges $214.79 for a detached garage.

What a 400 sq ft addition costs, line by line

A Calgary renovator's breakdown for an addition of up to about 400 sq ft shows where the money goes. Framing carries the widest range, then the foundation and the exterior shell.

At 400 sq ft that is about $220 to $450 a square foot, in line with the $225 to $450 the same firm quotes for room additions in Calgary. Alberta charges 5% GST on the contract, so ask whether a quote includes it.

Costs outside the per-square-foot price

Per-foot prices cover construction. Soft costs add 15 to 25% to the project total on a Toronto builder's 2026 figures, and these lines often sit outside the main quote:

• Design. On the same builder's figures, an architect charges about 12 to 15% of construction cost in Toronto. In Kitchener-Waterloo, the permit drawings, engineering, site and grading plans come to $10,000 to $25,000 before construction starts.
• Structural engineering. $3,000 to $8,000+, more for a second or third storey.
• Zoning approval. If the design needs a minor variance, Toronto's Committee of Adjustment charges $2,228.98 in 2026 for an addition to a house of three units or less, and planning or legal help adds $5,000 to $15,000+.
• Sales tax. 13% HST in Ontario, 15% in New Brunswick, Newfoundland and Labrador and Prince Edward Island, 14% in Nova Scotia and 5% GST in Alberta. In BC the contractor pays 7% PST on the materials inside its price and charges 5% GST on the contract.
• Contingency. 10 to 15% on top of everything else.

Two rules can work in your favour. An addition that only enlarges the house pays no development charge in Toronto, where the City lists the enlargement of an existing dwelling unit as a legislated exemption. An addition built as a self-contained unit so a senior, or an adult eligible for the disability tax credit, can live with a relative may qualify for the federal multigenerational credit: 14.5% of up to $50,000 of qualifying costs, at most $7,250, for work completed in 2025, and 14%, at most $7,000, for 2026, since the credit follows the lowest federal tax rate that Finance Canada puts at 14% for 2026.

The GST/HST new housing rebate for owner-built houses is narrower: it treats an addition as a major addition only if it at least doubles the living space, and a family room, bedroom or sunroom on its own does not qualify.

Permit fees for a home addition in Toronto, Calgary and Edmonton

An addition changes the footprint or height of the house, so it needs a building permit and often a zoning review for setbacks and lot coverage. The fee is a small line next to design and engineering, and each city sets it differently: by floor area in Toronto, by size band in Calgary and by construction value in Edmonton.

How long a home addition takes

Design and approvals take about as long as the build. A Toronto builder's 2026 timeline runs as follows.

A second storey takes the existing roof off, and on the same builder's figures families typically move out for 5 to 7 months while it is built.

Addition or move?

Moving within Toronto costs $80,000 to $150,000 in land transfer tax, commission and moving on a Toronto builder's 2026 figures, before the price difference of a bigger house, and none of it adds floor area. A 500 sq ft rear addition at about $318,000 to $425,000 all in buys space you keep, but only where the lot, the zoning and the existing structure can take it.

What to check in a home addition quote