When a growing family outgrows a house, the choice is usually move or add on — and in Ontario's 2026 market, with land transfer taxes and moving costs stacked against relocating, additions deserve a serious look. Contractor-built additions in Ontario typically run $200–$400+ per square foot, putting a 400 sq ft addition at roughly $100,000–$200,000+.
That per-foot cost shocks people who compare it to new-build prices, but additions carry demolition, tie-in, foundation and permit costs that new construction spreads across a whole house. Figures below are NorthPeak planning estimates.
Cost by addition type
| Type | Typical size | Budget range |
|---|---|---|
| Bump-out (2–3 ft extension) | 50–150 sq ft | $20,000–$60,000 |
| Single-room ground addition | 200–400 sq ft | $60,000–$140,000 |
| Full rear/side addition | 400–800 sq ft | $120,000–$280,000+ |
| Second storey | 600–1,200 sq ft | $180,000–$400,000+ |
Why additions cost more per foot than new builds
- Demolition and tie-in: opening up an existing wall, matching rooflines and siding, and weaving new mechanicals into old systems.
- Foundation: the addition needs its own frost-depth foundation ($15,000–$40,000) unless built over an existing structure.
- Living through it: dust, noise and a construction zone for 3–6 months — some families budget temporary relocation.
- Second storeys: require structural engineering to confirm the existing foundation and framing can carry the load; sometimes the whole main floor needs reinforcement.
Permits, zoning and the timeline
Additions need full building permits plus zoning compliance — setbacks, lot coverage limits and height restrictions can shrink or kill a project before it starts. Budget $2,000–$5,000 for permits, drawings and engineering, and 2–4 months for approvals in busy Ontario municipalities. A Committee of Adjustment minor variance adds months if your plans exceed zoning. Talk to the municipal planning department before paying for detailed drawings.
Move vs. build test: add the addition cost to your current home's value, then compare with the all-in cost of buying bigger — purchase price plus land transfer tax, legal fees, moving costs and realtor commissions on selling (typically 4–5%). If the addition keeps you in a neighbourhood you love, it often wins.
Frequently asked questions
How much does a home addition cost in Ontario in 2026?
$200–$400+ per square foot contractor-built. A 400 sq ft addition runs roughly $100,000–$200,000+; second storeys cost more per foot.
Is it cheaper to build an addition or move?
Compare the addition cost against buying bigger: purchase price difference plus land transfer tax, legal fees, moving costs and ~4–5% realtor commissions on your sale. In expensive markets, additions often win.
Do I need a permit for a home addition in Ontario?
Yes — full building permits plus zoning compliance for setbacks, lot coverage and height. Budget $2,000–$5,000 for permits, drawings and engineering, and 2–4 months for approvals.
How long does a home addition take?
Construction typically takes 3–6 months; permits and design add 2–4 months before that. Second storeys and variances take longer.
Sources and methodology
- Vista Builders: Home Renovation Cost in Ontario (2026 Guide)
- Canada Mortgage and Housing Corporation (CMHC)
- HomeStars
This article provides general information for planning purposes, not professional advice or a quote. Cost figures are NorthPeak planning estimates unless a source is named; confirm current prices with licensed local contractors and professionals before making decisions.