Types of additions we build
- Second-storey additions on bungalows and one-and-a-half storey homes
- Rear and side additions for bigger kitchens, family rooms and primary suites
- Sunrooms, insulated for year-round use
- Garages, attached or detached, with loft suites above
- Garden suites, laneway homes and coach houses as additional residential units
Why second storeys cost more per square foot
A second storey has to sit on a foundation and walls that were never designed for it. An engineer checks the footings and framing, and we often reinforce them. The new roof, the stair that takes space on both floors, and protecting the house while the roof is open all add cost. That is why second storeys run higher per square foot than ground-level additions.
Additional residential units: building a second home on your lot
Ontario now lets most serviced residential lots hold up to three units: the main house plus two additional residential units (ARUs), inside the house or in a detached building. Each municipality sets its own details. Peterborough updated its rules in 2023 and offers pre-approved plans for detached units. Cramahe Township has a dedicated ARU review process. See our Peterborough ARU guide and Northumberland ARU guide.
What's not in the per-square-foot number
Design fees, structural engineering (often $2,000 to $5,000), permits, utility upgrades such as a larger electrical service, and a contingency. We list every one of these in your quote.
Ranges are typical 2026 Ontario market figures from published cost guides (Caliber Contracting, RenoQuotes), shown to help you plan. They are not a quote. Your project gets its own fixed price after a site visit, with every line item written out.
We work across Northumberland County (Colborne, Cobourg, Port Hope, Brighton), Quinte, Peterborough and the Kawarthas, with Barrie from early 2027.
Questions, answered
Most second-storey additions cost about $250 to $400 per square foot in 2026, so a 1,000 square foot second storey typically lands between $250,000 and $400,000 before design, engineering and permits.
Yes. Every home addition in Ontario needs a building permit, and many need a zoning review first. We prepare and file it.
Most likely. Ontario allows up to three units on most serviced residential lots, and each municipality sets size, setback and parking rules. We check your zoning at the first meeting.
Usually yes for rear and side additions. For a second storey, most families move out while the roof is open.