Attic Conversion Cost in 2026: Toronto and GTA Prices (CAD)
GTA attic conversion prices by scope from four Toronto renovation firms, budget shares, stair, bathroom and skylight add-ons, HomeGuide US benchmarks and GTA permit fees.
An attic conversion in Toronto costs $40,000 to $200,000 or more in 2026, depending on whether the roof has to change, based on RenoHouse's published pricing. An attic conversion turns unused roof space into a bedroom, office or suite, with a structural floor, insulation, stairs, wiring, drywall and often a dormer for headroom. To get local prices, start with our attic finishing services.
RenoHouse, Lepata, NovaCon and A Renovation figures are in CAD. HomeGuide figures are in USD. City fee schedules are 2026 rates. All figures were checked on October 22, 2026.
Key takeaways
- Light Toronto attic finish with no dormer: $40,000 to $70,000 (RenoHouse, CAD).
- Rear shed dormer plus finish on a Toronto semi: $80,000 to $130,000 (RenoHouse).
- Full third-floor suite with dormer and ensuite: $150,000 to $200,000 or more (RenoHouse).
- Most full GTA attic conversions: $120,000 to $230,000 or more (Lepata).
- Per square foot of new finished area: $200 to $400 (RenoHouse).
- US attic conversion to living space: $20,000 to $80,000 or more (HomeGuide, USD).
How much does an attic conversion cost in Toronto by scope?
A Toronto attic conversion costs $40,000 to $70,000 when the attic already has headroom and needs only finishing, says RenoHouse. Adding a rear shed dormer takes it to $80,000 to $130,000, and a full third-floor suite starts at $150,000. The roof sets the price: raising headroom costs far more than finishing the space under it.
| Scope | What it includes | Price | Source |
|---|---|---|---|
| Light attic finish | No dormer, 7'6" or more peak headroom; insulation, drywall, electrical, trim | $40,000 to $70,000 | RenoHouse |
| Rear shed dormer plus finish | Headroom across the back half of the attic, typical Toronto semi | $80,000 to $130,000 | RenoHouse |
| Front gable dormer plus finish | More architectural scope, heritage character review | $100,000 to $160,000 | RenoHouse |
| Full third-floor primary suite | Rear shed dormer, ensuite, walk-in closet, staircase upgrade | $150,000 to $200,000 or more | RenoHouse |
| Most full GTA conversions | Varies by size, structure, dormers, bathrooms, finishes | $120,000 to $230,000 or more | Lepata |
| Basic 500 sq ft conversion | Starting point before high-end finishes | From about $175,000 | NovaCon |
RenoHouse says its ranges include design, structural engineering, permits, framing, insulation, electrical, plumbing rough-in, drywall, flooring, paint and trim. It excludes extra reinforcement below the attic if the engineer finds the second floor cannot carry the new load. NovaCon says high-end conversions can exceed $250,000.
Planning an attic conversion in the GTA? Pro House Maintenance matches you with vetted, licensed and insured pros who give free written estimates. Compare attic finishing quotes in Toronto, attic contractors in Mississauga or attic finishing in Hamilton. To shortlist firms yourself, see the best general contractors in Toronto.
Where does the money go in an attic conversion?
Structure and mechanicals take the biggest share of an attic conversion budget. NovaCon puts electrical, plumbing and HVAC at 20% to 30% of the total and structural changes at 15% to 25%. A Renovation puts structural work, including floor reinforcement and dormers, at 30% to 40% of the budget.
| Budget line | Share of total |
|---|---|
| Electrical, plumbing and HVAC | 20% to 30% |
| Structural modifications | 15% to 25% |
| Finishing (drywall, flooring, paint) | 15% to 25% |
| Insulation and air sealing | 10% to 15% |
| Windows and exterior changes | 10% to 20% |
| Design and engineering | 5% to 10% |
| Stairs and access | 5% to 10% |
Engineering is a fixed early cost. RenoHouse says a structural engineer's fee for a dormer and finish design package typically runs $3,500 to $8,000. Ask for it as its own line, because you pay it before you know the final build price.
What do stairs, bathrooms and skylights add?
A proper staircase costs $8,000 to $15,000 in a Toronto attic conversion, says A Renovation, and an attic bathroom costs $18,000 to $30,000. Skylights add $2,000 to $5,000 each, and custom built-ins for the sloped walls add $3,000 to $8,000. These add-ons explain much of the gap between a $40,000 and a $130,000 quote.
- Staircase: $8,000 to $15,000, depending on complexity (A Renovation).
- Attic bathroom: $18,000 to $30,000, more than a basement bathroom because of plumbing runs (A Renovation).
- Skylights: $2,000 to $5,000 each (A Renovation).
- Built-ins under the slopes: $3,000 to $8,000 (A Renovation).
- Engineer's dormer and finish package: $3,500 to $8,000 (RenoHouse).
Built-ins and trim are carpentry work. For those line items, compare our carpenter cost guide. If the attic needs new insulation first, our attic finishing statistics cover rebates and R-values.
How do US attic conversion prices compare?
A US attic conversion to living space costs $20,000 to $80,000 or more, says HomeGuide, and finishing an attic only for storage costs $5,000 to $20,000 (USD). A 400 square foot attic runs $20,000 to $60,000. Those USD figures sit well below the GTA ranges above, which RenoHouse says include design, engineering and permits.
| Item | Cost (USD) |
|---|---|
| 400 sq ft finished attic | $20,000 to $60,000 |
| 600 sq ft finished attic | $30,000 to $90,000 |
| Bedroom, office or bonus room | $20,000 to $45,000 |
| Primary suite (bedroom and full bath) | $50,000 to $100,000 or more |
| Attic dormer addition | $19,600 to $54,900 |
| Raising the roof | $30,000 to $70,000 |
Source: HomeGuide, Cost to finish an attic.
HomeGuide notes that building codes require at least 50% of the room to have a 7-foot ceiling. That rule is why so many older GTA attics need a dormer before they can become a bedroom.
Do you need a permit for an attic conversion in the GTA?
Yes. Lepata says turning an attic into habitable space needs a building permit anywhere in Toronto and the GTA. Fees are charged per square metre, and Toronto counts habitable attics in that floor area. In 2026, Toronto charges $11.53 per square metre for residential interior alterations, Mississauga $6.84 and Brampton $5.34.
| City | Rate | Minimum fee | Source |
|---|---|---|---|
| Toronto | $11.53 per m2 (Group C interior alterations) | $214.79 | City of Toronto |
| Mississauga | $6.84 per m2 (residential alterations) | $244.00 | City of Mississauga |
| Brampton | $5.34 per m2 (residential alteration) | $326.21 | City of Brampton |
A dormer changes the roof, so it is more than an interior job. Toronto lists a separate $6.20 per square metre rate for re-roofing with structural work or a raised roof, and a zoning certificate costs 25% of the building permit fee. For permit timelines and penalties, see our building permit statistics.
How do you get an accurate attic conversion quote?
Start with the headroom: measure the height at the peak and how much of the floor sits above 7 feet. Ask each contractor whether the plan needs a dormer, floor reinforcement or a new staircase, and get an engineer's assessment in writing. Ask for an itemized quote that names who pulls the permit, and compare at least three on the same scope.
If the job grows into a full extra storey, our home addition cost guide prices that route, and the general contractor cost guide explains GC fees. Compare free quotes through our attic finishing hub.
Sources
- RenoHouse, Attic Conversion Toronto: Dormer Addition
- Lepata Construction, Attic Renovations and Conversions in Toronto and the GTA
- NovaCon Construction, The Ultimate Guide to Attic Conversions in Toronto
- A Renovation, Basement and Attic Finishing Toronto
- HomeGuide, How Much Does It Cost to Finish an Attic?
- City of Toronto, Building Permit Fees
- City of Mississauga, 2026 Classes of Permits and Fees
- City of Brampton, 2026 Permit Fee Schedule
Frequently Asked Questions
How much does an attic conversion cost in Toronto?
RenoHouse puts a Toronto attic conversion at $40,000 to $70,000 for a light finish with no dormer, $80,000 to $130,000 with a rear shed dormer and $150,000 to $200,000 or more for a full third-floor suite in 2026. Lepata puts most full GTA conversions at $120,000 to $230,000 or more.
How much does an attic conversion cost per square foot in the GTA?
RenoHouse prices Toronto attic conversions at $200 to $400 per square foot of new finished area, including design, engineering and permits. A Renovation quotes $45 to $100 or more per square foot for simpler attic finishing. The gap comes from structure: dormers, new stairs and floor reinforcement cost far more than drywall and insulation.
How much does a dormer add to an attic conversion?
In RenoHouse's Toronto pricing, a rear shed dormer conversion costs $80,000 to $130,000, against $40,000 to $70,000 for a light finish with no dormer. A front gable dormer runs $100,000 to $160,000. In the US, HomeGuide puts an attic dormer addition alone at $19,600 to $54,900 (USD).
Do I need a permit to convert an attic in Toronto?
Yes. Lepata says any conversion of an attic into habitable living space needs a building permit in Toronto and the GTA. Toronto counts habitable attics in the floor area it uses to set the fee, and its 2026 rate for residential interior alterations is $11.53 per square metre, with a $214.79 minimum.
How much does it cost to add a bathroom in an attic?
A Renovation puts an attic bathroom at $18,000 to $30,000 in Toronto, more than a basement bathroom because of plumbing runs. RenoHouse includes an ensuite in its full third-floor suite tier of $150,000 to $200,000 or more. HomeGuide puts a US attic bathroom at $20,000 to $60,000 (USD).
Is an attic conversion cheaper than an addition?
Often, yes, per square foot of new space. NovaCon says Toronto additions run $350 to $400 or more per square foot, and RenoHouse prices attic conversions at $200 to $400. A conversion uses the existing roof and foundation, but a dormer, new stairs and floor reinforcement can push it toward addition prices.
Is Pro House Maintenance free for attic conversion quotes?
Yes. Pro House Maintenance is free for homeowners. You describe your attic project once, and we match you with vetted local pros who give free written estimates. You compare the quotes and choose who to hire, with no obligation to book.