Whether your family is growing, the kids need their own space, or a parent is moving in, the need for more room can quickly become a necessity. But before you dive in, a few key questions come to mind: How much does a home addition cost in Quebec? What factors should you consider for such a significant investment? Is it better to expand or move?
Whatever your needs or reasons to build a home addition, this guide has everything you need to plan your project: Price tables, real-world examples drawn from actual projects, and all the details you need to build a realistic budget.
How much does a home addition cost in Quebec?
Adding a small bump-out to your property doesn't require the same resources as adding a full storey with three bedrooms and a bathroom. In other words, the cost of a home addition varies considerably depending on the type of project.
To give you an idea of what to budget for, here are estimated price ranges for the Quebec market, based on turnkey projects (labour and materials included).
Project type | Typical square footage | Estimated price range |
|---|---|---|
Lateral extension (bump-out) | 50–100 sq ft | $25,000–$60,000 |
Room addition | 100–200 sq ft | $50,000–$120,000 |
Major addition (single-storey) | 300–600 sq ft | $100,000–$220,000 |
Full second storey addition | 600–1,200 sq ft | $150,000–$350,000+ |
In-law suite | 400 – 700 pi² | $120,000–$260,000 |
These figures are reference points only, provided for general guidance. Every home addition project is unique and has its own characteristics; only a personalized quote will give you a reliable estimate. RenoAssistance by Desjardins can help you get comparable quotes from multiple verified contractors.
Price per square foot: An essential indicator for planning
The cost per square foot ($/sq ft) is the go-to reference in residential construction for estimating and comparing home addition costs on a common basis.
Here are the prices to expect for the most common types of home addition extensions.
Good to know
The larger the area you're adding, the lower the cost per square foot tends to be. This is the economies-of-scale effect: Fixed costs such as plans, permits, and site mobilization are spread over a larger surface area, which reduces the unit cost per square foot.
Single-storey addition
Estimated price: $200–$350/sq ft
A single-storey addition refers to any lateral or rear extension built at the same level as the existing ground floor. It is typically built on poured foundations or a concrete slab.
The price for this type of home addition generally includes:
Foundations
Framing and structure
Thermal insulation
Exterior cladding
Interior finishes
Keep in mind
A single-storey addition is a solid, long-lasting option, particularly well-suited to single-floor properties with enough land available.
Second storey addition
Estimated price: $250–$400/sq ft
Adding a second storey is often the preferred solution when the lot doesn't allow for ground-level expansion.
The cost of a second storey addition is generally higher per square foot than other types of home additions, for two main reasons:
It requires a structural assessment of the existing load-bearing walls.
Demolishing and replacing the roof is a significant budget item.
Keep in mind
In some cases, temporary relocation will be necessary during the most intensive phases of construction — another cost to factor into your budget!
Home addition on helical piers
Estimated price: $180–$300/sq ft
Choosing a home addition on helical piers is an excellent way to save money and speed up your timeline. Instead of excavating and pouring concrete, metal screws are driven into the ground to support the structure.
This approach offers several advantages:
Installation is much faster and can often be completed within a few days.
The cost is generally lower than a poured-foundation home addition.
The impact on landscaping is minimal.
Keep in mind
Home additions on helical piers are not suited to all soil types or project types and are not accepted by all municipalities. Consult specialists to assess whether this approach is right for your project.
What factors affect the cost of a home addition?
A home addition budget depends on a whole range of technical, regulatory, and human factors.
Square footage added
The larger the area to cover, the higher the total project cost. That said, the cost per square foot will tend to decrease. If your addition covers less than 100 sq ft, fixed costs will represent a proportionally larger share of your total budget.
Foundation type
The choice of foundation directly affects the duration and total cost of your project.
Poured foundations: More durable but more expensive, ideal for home additions with a basement.
Helical piers: A faster and more economical option, well suited to lightweight extensions.
Concrete slab: A good compromise for an extension without a basement.
Materials and finish level
The materials you choose for your interior finishes can significantly affect the cost of your home addition.
Flooring: Choosing hardwood over laminate makes a notable difference in cost, and in perceived property value.
Windows: Triple-glazed windows cost more upfront than standard models, but can generate meaningful heating savings over time.
Cabinets and countertops: Using premium materials such as quartz, marble, or granite for your kitchen counters or bathroom cabinetry can push the budget up by several thousand dollars.
Architectural complexity
Certain features, such as a mansard roof, an irregular slope, or a complex junction with the existing structure, can generate significant cost overruns. For this type of complexity, bringing in architectural specialists is often essential and pays off in the long run.
Plumbing and electrical work
Adding a bathroom or kitchen to your home expansion can have a considerable impact on the final bill. This type of work can easily cost between $15,000 and $40,000, depending on the room size and the fixtures involved.
Location and municipal requirements
more than in rural areas. Municipal requirements also vary from one city to the next.
Setback requirements: Each municipality sets a minimum distance between the building and property lines, which can limit the maximum size of your addition.
Maximum building height: Building height is sometimes restricted in certain zones, which may rule out adding a storey.
Floor area ratio (FAR): This ratio determines what proportion of the lot can be covered by structures.
Building permit cost: Typically between 0.5% and 1% of total construction costs, depending on the municipality.
It is strongly recommended to consult your municipality's urban planning department before starting any home addition work, to avoid unexpected costs.
Time of year and contractor availability
Spring and summer are peak season for Quebec's construction industry, which leads to longer wait times and higher prices. Planning your home addition project for fall or winter is often a smart strategy, both for pricing and contractor availability.
Real-world cost examples for each type of addition
Because every home addition has its own costs and specificities, here are five concrete examples of projects that RenoAssistance by Desjardins regularly handles.
Adding a bedroom or home office
Scenario: Since working from home three days a week became the norm, David wants to add a 150 sq ft home office to his house in Laval, a project that has surged in popularity since the rise of remote work.
Estimated price range: $50,000–$90,000
Project-specific factors: Enhanced acoustic insulation and an electrical setup suited to remote work needs.
Kitchen or living room extension
Scenario: Marie-Ève has been dreaming of a bigger living space for entertaining. After reviewing her options with the RenoAssistance by Desjardins team, she goes with a lateral bump-out, a few extra feet that give her the result she is looking for without changing the character of her home's architecture.
Estimated price range: $60,000–$130,000
Project-specific factors: Plumbing connections (if it's a kitchen), adding large windows to maximize natural light, and selecting the right flooring.
Creating an in-law suite
Scenario: Wanting to give her mother, who is losing her independence, the best possible quality of life, Nathalie decides to build an in-law suite (a self-contained living unit integrated into her home) that offers both closeness and privacy.
Estimated price range: $120,000–$160,000
Project-specific factors: Private entrance, accessible bathroom, secondary kitchen, and wheelchair-accessible access.
Good to know
Programs such as Hydro-Québec's LogisVert, as well as certain tax credits for caregivers, can offset part of the costs for this type of project. Contact our team to learn more.
Full second storey addition
Scenario: With three fast-growing kids, Sophie and Marc are starting to feel cramped in their South Shore bungalow. Unable to afford a move, the couple decides to add a full second storey so the whole family has room to breathe. Despite the significant costs, Sophie and Marc know this type of addition will deliver strong returns in added property value.
Estimated price range: $150,000–$350,000+
Project-specific factors: Structural assessment of existing load-bearing walls, roof demolition and reconstruction, and possible temporary relocation.
Attached garage or double garage addition
Scenario: As a new homeowner without a garage, Patrick is tired of scraping his car every morning and wants to build an attached garage. And since he also wants to increase his home's market value, he decides to add a livable space above the garage while he's at it.
Estimated price range: $60,000–$120,000 for a garage only; $130,000–$220,000 for a garage with a livable space above.
Project-specific factors: Heated concrete slab, motorized sectional door, and enhanced insulation if livable space is included above.
Often-overlooked costs to factor in
Even the most prepared homeowners can miss important budget items when planning a home addition.
Here are some costs to anticipate so there are no unpleasant surprises.
Professional fees: These can represent 5%–15% of your total project cost, depending on complexity.
Plans and technical drawings: Budget between $2,000 and $8,000 for this line item.
Building permit: Check with your local municipality to find out the cost of a building permit for a home addition and factor it into your budget from the start.
Geotechnical studies: Does your lot have particular characteristics? Budget between $1,500 and $4,000 for a site assessment.
Taxes (GST and QST): Materials and labour are subject to approximately 15% in taxes, so don't forget to include them.
Temporary relocation: Will your home be uninhabitable during part of the work? Budget between $3,000 and $8,000 per month for temporary housing.
Landscaping: Often left for last, landscaping work is frequently necessary after a home addition, since the construction site can leave its mark. Budget between $3,000 and $15,000 to restore your yard.
Contingency reserve: Set aside an extra 10%–15% to absorb unexpected costs.
Extending or moving? The other question worth asking!
Take the time to weigh both options to determine which one best fits your needs.
Here is a quick comparison table to help you make an informed decision.
Criterion | Expanding | Moving |
|---|---|---|
Average cost | $50,000–$350,000 | Purchase price of new property + $50,000–$80,000 in transaction costs |
Welcome tax | Not applicable | A few thousand dollars to over $30,000 (depending on property value) |
Timeline | 3–12 months | 3–6 months |
Impact on daily life | Temporary (construction site) | Permanent (new neighbourhood) |
Added value | Approx. 15%–30% more | Varies with market |
Neighbourhood attachment | Preserved | Potentially lost |
A project simplified from A to Z with RenoAssistance by Desjardins
Planning a home addition means navigating dozens of technical, administrative, and financial decisions. It's not always easy to know where to start! Fortunately, RenoAssistance by Desjardins offers you several concrete advantages to bring your project to life.
Needs assessment: Our advisory team evaluates your project and priorities at no charge.
Network of verified home addition contractors: We recommend contractors who are rigorously screened and hold a valid Régie du bâtiment du Québec (RBQ) licence.
Comparable quotes: We provide multiple quotes from qualified contractors so you can compare on a level playing field.
End-to-end support: We guide you through every step of your project, from your first call to the final walkthrough.
Your project starts here
Get a free, no-obligation estimate. Our advisory team will contact you within 24 to 48 business hours.
