Home Addition Cost in Montreal — 2026 Complete Price Guide
Planning a home addition in Montreal? Whether you need an extra bedroom, a larger kitchen, or a full second floor, understanding the costs involved is the first step. At Nael Construction, Montreal’s trusted renovation contractor, we’ve completed dozens of home additions across the Greater Montreal area — from single-room extensions to full second-story builds. This guide breaks down every cost factor so you can budget with confidence. Get a free estimate for your home addition project.
Average Home Addition Cost in Montreal (2026)
The cost of a home addition in Montreal ranges from $150 to $400 per square foot, depending on the type of addition, structural requirements, and finishes. Here’s the quick breakdown:
- Ground-floor room addition: $150–$250/sqft — A 200 sqft addition costs $30,000–$50,000
- Second floor addition: $250–$400/sqft — A 1,000 sqft second floor costs $250,000–$400,000
- Bump-out extension (kitchen/bathroom): $200–$350/sqft — A 50 sqft bump-out costs $10,000–$17,500
- Garage conversion to living space: $80–$150/sqft — A 400 sqft garage conversion costs $32,000–$60,000
- Sunroom or three-season room: $120–$250/sqft — A 200 sqft sunroom costs $24,000–$50,000
For a typical Montreal single-family home addition of 300–500 square feet, most homeowners spend between $60,000 and $150,000 all-inclusive.
Home Addition Cost Breakdown by Type
Your addition type is the biggest cost driver. Here’s how each option compares for Montreal homes:
Ground-Floor Room Addition
The most common type of home addition in Montreal. Involves extending the ground floor with a new foundation, walls, roof, and finishes. Costs $150–$250/sqft installed. Typical projects include adding a bedroom, expanding a living room, or creating a home office. Timeline: 6–10 weeks. Best for: homes with available yard space and straightforward foundation work.
Second Floor Addition (Agrandissement)
Adding a full second floor to a bungalow or single-story home is the most complex and expensive type of addition. The existing foundation must be evaluated and often reinforced to support the additional load. Costs $250–$400/sqft because it requires structural engineering, foundation reinforcement, new framing, roofing, plumbing, electrical, and HVAC extension. A typical 1,000 sqft second floor addition in Montreal costs $250,000–$400,000. Timeline: 12–20 weeks. This is the project type driving the surge in « agrandissement maison » searches across Laval, Outremont, and Westmount.
Bump-Out Extension
A bump-out is a small extension — usually 2–4 feet deep — that enlarges an existing room without requiring a full foundation. Common for expanding a kitchen or bathroom. Costs $200–$350/sqft because the per-square-foot cost is higher for small additions (fixed costs like permits and contractor setup are spread over fewer square feet). Timeline: 3–6 weeks. Best for: homeowners who need just a bit more space without a major addition.
Garage Conversion
Converting an existing garage into living space is one of the most cost-effective ways to add square footage. Since the structure and foundation already exist, costs are lower at $80–$150/sqft. The work involves insulation, drywall, flooring, electrical, and HVAC. A 400 sqft garage conversion costs $32,000–$60,000. Timeline: 4–8 weeks. Note: this reduces or eliminates parking, which may affect resale value in some Montreal neighborhoods.
Sunroom or Three-Season Room
A sunroom adds bright, comfortable living space with large windows and minimal structural work. Costs $120–$250/sqft. A 200 sqft sunroom costs $24,000–$50,000. Timeline: 3–6 weeks. Best for: homeowners who want additional living space with natural light and garden views.
Cost Factors That Affect Your Home Addition
Beyond the type of addition, several factors influence the final price:
Foundation and Structural Work
If your addition requires a new foundation (concrete footings, foundation walls, slab), expect to add $15,000–$30,000 to the project. Second-floor additions may require reinforcing the existing foundation with steel beams or additional footings — costs range from $10,000–$40,000 depending on the existing structure’s condition.
Permits and City Requirements
Montreal building permits for home additions cost $500–$3,000 depending on the project scope and borough. Each Montreal borough has specific setback requirements, height limits, and zoning regulations. Plateau-Mont-Royal, Outremont, and Westmount have stricter heritage and aesthetic requirements that can add design and approval costs. Plan for 4–8 weeks of permit approval time.
Plumbing and Electrical
Extending plumbing and electrical to the new space costs $5,000–$20,000 depending on distance from existing systems. Adding a bathroom in the addition adds $8,000–$15,000 for plumbing alone. Electrical rough-in for a 300 sqft addition typically costs $3,000–$6,000.
HVAC Extension
Extending heating, ventilation, and air conditioning to the new space costs $3,000–$10,000. Options include extending existing ductwork, adding a mini-split system ($3,000–$5,000 per unit), or installing baseboard heaters ($1,500–$3,000). Montreal’s cold winters make proper insulation and heating critical — don’t cut corners here.
Interior Finishes
Finishes are where you can control costs. Standard finishes (laminate flooring, basic cabinetry, standard fixtures) cost $30–$60/sqft. Premium finishes (hardwood, custom cabinetry, high-end fixtures) cost $60–$120/sqft. For a 300 sqft addition, finish costs range from $9,000 to $36,000 depending on your choices.
Roofing and Exterior
Tying the new addition’s roof into the existing roof costs $5,000–$15,000. Exterior cladding (brick, siding, stucco) to match the existing home costs $8,000–$20,000 for a typical addition. Matching exterior materials is important for curb appeal and resale value — especially in Montreal’s older neighborhoods where brick facades are common.
Home Addition Cost by Montreal Neighborhood
Costs can vary by neighborhood due to permit requirements, access constraints, and labor availability:
- Laval: Slightly lower costs due to easier site access and more flexible zoning. Second-floor additions popular for bungalows.
- Outremont: Higher costs due to heritage requirements, strict zoning, and premium finishes expected in the area.
- Westmount: Highest costs — permit process is rigorous, architectural requirements are strict, and homes often require specialized structural work.
- Saint-Laurent: Moderate costs, good for ground-floor extensions on larger lots.
- Brossard/Longueuil: Lower costs, favorable for larger additions on South Shore properties.
Is a Home Addition Worth It?
A well-executed home addition typically returns 60–80% of its cost in increased home value in the Montreal market. Second-floor additions and kitchen expansions tend to have the best ROI. Here’s when a home addition makes sense:
- You love your neighborhood and don’t want to move
- Your lot has space for a ground-floor extension
- Your home’s current value supports the investment (don’t over-improve for the street)
- Your foundation can support the additional load (for second-floor additions)
- You need specific space — a bedroom for a growing family, a home office, or a larger kitchen
If moving costs $30,000–$50,000 in realtor fees, moving expenses, and closing costs, a $60,000 addition that keeps you in your neighborhood can be the smarter financial choice.
How to Budget for a Home Addition in Montreal
- Get a professional assessment first. A structural evaluation ($500–$1,500) determines if your foundation can support the addition. This is critical for second-floor projects.
- Set a realistic budget range — not a single number. Plan for the midpoint of the range and set aside 15–20% as contingency.
- Check zoning and permit requirements with your borough before starting design work. Setback rules and height limits may constrain what’s possible.
- Get at least three quotes from licensed Montreal contractors (RBQ licensed). Compare scope, not just price.
- Plan for temporary relocation if the addition affects your kitchen or bathroom — budget $3,000–$8,000 for temporary housing during construction.
FAQ: Home Addition Costs in Montreal
How much does a home addition cost in Montreal?
A home addition in Montreal costs $150–$400 per square foot depending on the type. A ground-floor room addition costs $30,000–$50,000 for 200 sqft. A second-floor addition costs $250,000–$400,000 for 1,000 sqft. Bump-outs and garage conversions are less expensive options.
Do I need a permit for a home addition in Montreal?
Yes, all home additions require a building permit from your Montreal borough. Permit costs range from $500–$3,000 depending on project scope. Approval takes 4–8 weeks. Some boroughs (Outremont, Westmount, Plateau) have additional heritage or aesthetic requirements.
How long does a home addition take in Montreal?
Timeline depends on scope: bump-outs take 3–6 weeks, garage conversions 4–8 weeks, ground-floor additions 6–10 weeks, and second-floor additions 12–20 weeks. Add 4–8 weeks for permit approval before construction begins.
Can I add a second floor to my Montreal bungalow?
Yes, but it requires a structural engineer to assess whether your foundation can support the additional load. Foundation reinforcement may be needed. Second-floor additions are increasingly popular in Laval and Montreal suburbs with single-story homes — search interest for « agrandissement maison » has surged in 2026.
What is the cheapest way to add space to my home?
A garage conversion ($80–$150/sqft) or a sunroom ($120–$250/sqft) are the most affordable options. A bump-out extension is also cost-effective for small expansions. These avoid the foundation and structural costs of a full addition.
Start Your Home Addition Project
A home addition is a significant investment, but it can transform your living space and increase your property value. The key is working with an experienced contractor who understands Montreal’s building codes, permit processes, and structural requirements. At Nael Construction, we handle every aspect of your home addition — from design and permits to construction and finishing. Contact us for a free estimate and let’s discuss how to add the space your family needs.
Last updated: July 2026. Costs are estimates based on current Montreal market rates. Actual costs vary based on project scope, materials, and site conditions.