Home addition cost per square foot in Ontario runs about $110 to $320. An addition costs more per foot than a renovation because you are building new foundation, framing, roof, and envelope, not just refitting an existing room. A 400 square foot addition at a premium finish lands near $66,000 in Listowel and near $82,000 in the GTA.
By region and finish
Addition rates per square foot
| Service area | standard | premium | luxury |
|---|---|---|---|
| Toronto & GTA | $140/ft² | $205/ft² | $320/ft² |
| Hamilton & Niagara | $135/ft² | $195/ft² | $305/ft² |
| Kitchener-Waterloo, Cambridge & Guelph | $125/ft² | $185/ft² | $290/ft² |
| Listowel & Perth County | $110/ft² | $165/ft² | $255/ft² |
| Other Southwestern Ontario | $120/ft² | $175/ft² | $270/ft² |
Rates match the figures behind our calculators. They cover the addition shell and finishes. Tie-ins to the existing house (matching the roofline, extending HVAC) are project-specific.
What moves the price
Three cost drivers
- Foundation type. A slab is cheaper than a full basement under the addition.
- Roof tie-in. Matching an existing roofline cleanly costs more than a simple shed roof.
- Services. Extending HVAC, plumbing, and electrical into the addition, and whether the existing panel and furnace can carry the load.
Your addition
Get a number for your project
Enter the addition’s square footage and finish level for a cost range and the resale value it adds.
Open the home addition cost calculatorRelated
Keep reading
See how to calculate the home price increase from a renovation, or read about custom home and addition work in Perth County.