Estimate your home addition cost
Pick the project type, the approximate size and anything else on the job. The calculator returns a typical range for your project. It is a planning estimate, not a quote. Lot access, foundation conditions and permit scope move the real figure more than size alone, and none of those can be assessed from a form.
Choose the project type, scope, and finish level. Your estimate updates instantly as you refine the details.
1. What are you adding?
2. About how big is the new space?
3. Anything else on the job?
Ottawa price ranges by addition type
Structural additions are priced per square foot; smaller-scope projects are priced as a full-project total.
Per-square-foot additions
$325-$625 per sq ft
Second-storey addition: $385-$525 per sq ft
Single-storey rear or side addition: $325-$475 per sq ft
Small bump-out extension: $415-$625 per sq ft
Full-project additions
$25,000-$150,000
Single-room addition (bedroom or office): $50,000-$100,000
Kitchen addition: $75,000-$150,000
Garage addition, single or double: $50,000-$120,000
Attic conversion or dormer: $50,000-$120,000
Sunroom addition: $25,000-$70,000
Conversions and secondary space
$25,000-$120,000
Garage conversion to living space: $25,000-$85,000 depending on tier
Basement addition (finishing only): $7-$23 per sq ft
In-law suite / secondary dwelling unit build-out: roughly $60,000-$120,000
Egress window and window-well work priced after inspection
Three things that move a quote more than size
Square footage sets the starting point. These decide where in the range you land.
What the foundation has to do
Founding a new footing below frost depth, commonly treated as about 1.5 m locally, and accounting for Champlain Sea clay where it is present, changes the foundation line on your quote more than the square footage does.
Whether egress work is involved
A basement secondary suite or a below-grade bedroom often needs a new egress window and window well sized to the Ontario Building Code, priced once we've inspected the space.
Permit scope and review time
Permit fees typically run $1,500-$12,000 depending on the addition type, and permits typically take 4 to 12 weeks to issue, longer for a full secondary suite.
Questions about the calculator
Why does the calculator give a range instead of a price?
Because the two biggest variables can't be entered into a form: what the foundation has to do, and whether the project touches egress or permit-scope work. Those move a quote by thousands more than square footage does.
Are the permit fees included in the calculator's range?
Permit fees can be added as an optional line in the calculator, shown at their typical range rather than folded silently into the rate, so you can see them separately.
Which projects does the calculator cover?
Second-storey, rear and side additions, bump-outs, kitchen, sunroom, screened porch, attic, basement and garage projects, plus permit, design and walkout add-ons.
Does the calculator cover a commercial building addition?
No. Commercial additions are scoped and quoted individually against the property's use and occupancy requirements, so contact us directly for that kind of project.