Quick answer: A home addition adds living space to your house, either out the back or side, or up with a new storey. In Toronto every addition needs a building permit. Plan on 2 to 6 months for design and approvals and 5 to 9 months of construction. As a rough budget, additions run $300 to $500 per sq ft, depending on finishes and the type of work.
By Shedrack Idemudia, President, 905 Reno. Photo above: Powburn Pl, Toronto, the bungalow before, and after our second storey addition and full renovation.
Most families who call us about an addition don’t want to leave. They like the street, the schools and the neighbours, and moving means land transfer tax, real estate fees and starting over further out. An addition gets you the space without giving any of that up.
This guide covers what we walk every homeowner through at the first site visit: which kind of addition fits the house, what it costs, how long the permit and the build take, and whether you can stay home while we work.
Which addition fits your house
Building out or going up depends on your lot, your zoning and how the house is built. Not sure of the difference? Read addition or extension: which fits your house.
Rear addition
Builds out the back for a bigger kitchen and family room. Often the family can stay home for most of it.
Second storey
Adds a full floor without giving up the yard. It’s how a 2-bedroom bungalow becomes a 4-bedroom family home. Why families add a second storey.
Two-storey rear addition
More room on the main floor and a bedroom or primary suite upstairs, built in one go.
Third floor or attic conversion
Turns the attic or roof into a bedroom and ensuite, sometimes with a deck.
Bump-out
A small extension that adds a few feet to one room, like a kitchen or mudroom. What a bump-out costs.
Side addition
Uses side yard space on wider lots, if the setbacks allow it.
What a home addition costs in Toronto
As a rough budget, additions, second storeys and attic conversions run $300 to $500 per sq ft. Where your job lands in that range depends on:
- The foundation, and whether the addition gets a basement under it
- Structural work: new beams, strengthening the existing walls or footings
- Whether a kitchen or bathroom goes in the new space
- Finishes: flooring, windows, cabinets and fixtures
- How much of the existing house gets renovated at the same time
For a full breakdown, see our home addition cost guide.
How it works: Design. Permit. Build.
We design and build together, so the cost is checked while the drawings come together. Plan on 2 to 6 months for design and approvals before construction starts.
- 1Site visit and budget range1 to 2 weeks
- 2Design and drawings2 to 6 weeks
- 3Structural engineering1 to 2 weeks
- 4Building permit1 to 4 months, longer with a variance
- 5Construction5 to 9 months, depending on size
Permits and zoning in Toronto
Every addition needs a building permit in Toronto, whether it goes out the back or up. Drawings, structural engineering and a zoning review come first.
Zoning sets how deep you can build, how close to the side lot lines and how tall. If the design goes past those limits, it needs a minor variance from the Committee of Adjustment before the permit, which adds months.
The City aims to review a complete house application within 10 business days. Incomplete files or examiner comments add time. The permit for our Eileen Ave addition took about 3 months. We handle the drawings, engineering and permit application as part of our design-build process.
Additions we’ve built
566 Delaware Ave N: bungalow to 3 storeys
Rear and front extensions plus a new third floor, about 2,000 sq ft, with a full gut inside. We strengthened the foundation, underpinned the basement and repoured the slab. About 9 months of construction.
Eileen Ave: two-storey rear addition
About 1,000 sq ft: a rear addition with a full basement under it, a second-floor addition above and an interior remodel. About 7 months of construction.
Powburn Pl: second storey and full renovation
Designed, permitted and built by one team: a new second storey on a bungalow and a full home renovation.
Logan Ave: attic conversion
The attic turned into a third-floor bedroom and ensuite with a double vanity, alongside a rear addition and a rooftop deck.
Our second-storey addition on a small bungalow was featured on January 11, 2025. The homeowner: “It was more economical to put on a second storey and (it gave us) control over what it looked like.”
Can you live at home during an addition?
For a rear extension, the family can often stay for most of the job. For a second storey, the roof comes off and the house is open to the weather for part of the build, so most families move out. There are also times when the power or water is shut off while we work. We plan the schedule so the roof-off stage is as short as possible.
Questions we get asked
Do I need a permit for a home addition in Toronto?
Yes. Every addition needs a building permit, plus a minor variance if the design goes past the zoning limits.
How long does a home addition take?
Plan on 2 to 6 months for design and approvals and 5 to 9 months of construction, depending on the size.
How much does a home addition cost in Toronto?
As a rough budget, $300 to $500 per sq ft, depending on finishes and the type of work.
Is it cheaper to build up or out?
It depends on your foundation, your lot and your zoning. We check all three at the site visit before anything gets drawn.
Do you handle the drawings and permit?
Yes. Drawings, engineering and the permit application are part of our design-build process.
What’s the most common mistake?
Getting full drawings done before anyone has priced the build, then finding out the design is over budget. Before you hire anyone, read our 10 questions to ask a contractor.
Thinking about an addition?
Send us your survey or a few photos and we’ll come out, walk the house with you and tell you what your lot allows. Site visits are free. See our home additions and extensions page, or email Info@905reno.ca.
Design. Permit. Build. We stand behind every space we build.
