How much does a home addition cost in Quebec in 2026?
A home addition in Quebec usually costs $225 to $400 per sq ft turnkey, before taxes. A 200 sq ft room on piles often runs $45,000 to $70,000, while a full second storey easily exceeds $200,000. The foundation type, the connection to the existing house and the plans make the biggest difference.
Quebec price ranges in 2026
Quebec market estimates, updated October 2026, before taxes (GST and QST extra). These are not guaranteed prices: costs vary by region, building and materials, and only a written quote based on your project gives an actual price.
| Addition type | Price per sq ft (turnkey) | Sample budget |
|---|---|---|
| On helical piles | $225 – $350 | 200 sq ft room: $45,000 – $70,000 |
| On a concrete slab | $250 – $350 | 300 sq ft room: $75,000 – $105,000 |
| On a full foundation with basement | $300 – $400 | 400 sq ft: $120,000 – $160,000 |
| Second-storey addition | $250 – $350 | 800 sq ft: $200,000 – $280,000 |
| Architect or technologist plans | — | $3,000 – $15,000 |
What drives the price
- The foundation: piles, slab or full foundation with basement.
- Tying into the house: opening the existing wall, joining rooflines, extending heating and electrical.
- Whether the existing structure can carry another storey, to be checked by an engineer.
- Plumbing: an addition with a kitchen or bathroom costs more than a bedroom or living room.
- Zoning: setbacks, maximum height and allowed lot coverage.
Mistakes to avoid
- Asking for quotes without plans: each contractor then imagines a different project.
- Underestimating the cost of tying into the existing building.
- Having plans drawn before checking zoning with the municipality.
- Not planning where to live during a second-storey addition, when the roof is removed.
How to get reliable quotes
- Have plans prepared first, then give exactly the same plans to every contractor.
- Ask for a schedule by phase (foundation, framing, close-in, finishing) and the related payments.
- Check that the general contractor coordinates the subcontractors and that each holds the right RBQ licence.
- Check that the contractor holds a valid RBQ licence for this type of work in the Régie du bâtiment du Québec registry.
- Insist on a detailed written quote and compare at least three quotes line by line, not just the total.
Estimate your budget, then get quotes
Use the PRONEK estimator to get a range for your project, then post your project for free: it is sent to verified RBQ contractors, and no payment is requested before signing.
Frequently asked questions
How much does a 400 sq ft addition cost?
Depending on the foundation and finishes, expect around $90,000 to $160,000 before taxes.
Is it better to build out or add a storey?
Adding a storey saves yard space but requires a structure that can carry it. Building out is often simpler if the lot and zoning allow it.
How long does an addition take?
Usually 2 to 5 months of work, once plans and the permit are in hand.
Do I need a permit for a home addition?
Yes. An addition always requires a municipal permit and plans that meet the regulations.