We price a second-storey addition of 600 to 1,200 sq ft at $300,000 to $800,000 before HST in 2026. Work on the floor below, such as a new kitchen or bathrooms, adds to that. It's our range, not your quote: your price comes after James sees the house, and the first estimate is free. Below is what moves a job within the range, what quotes leave out, and what Durham Region, Ontario towns charge for the permit.
Key takeaways
- Our 2026 range for a second storey of 600 to 1,200 sq ft is $300,000 to $800,000 before HST, and work on the floor below, such as a kitchen or bathrooms, adds to it.
- Our permit drawings for an addition are $6,000 to $12,000. That's drawings only: permit fees, HVAC engineering, truss design, committee of adjustment applications and anything unforeseen are extra.
- In Whitby the building permit for an 800 sq ft second storey works out to $1,663, calculated from the Town of Whitby's 2026 fee schedule at $22.37 per square metre.
- A storey that only makes your house bigger pays no development charges, because the Development Charges Act excludes "the enlargement of an existing residential unit" (as of October 2026).
- Our Greenwood job in Toronto, a rear extension plus a new top storey, took 10 months including design, permits and construction.
What does a second storey cost in Ontario?
We price a second storey of 600 to 1,200 sq ft at $300,000 to $800,000 before 13% HST, as of October 2026. This page gives the whole-floor range, not a rate per square foot, because size is only one of the things that set the price.
Here are our 2026 ranges for a second storey and the work that often comes with it:
| Work | Our 2026 range, before HST |
|---|---|
| Second-storey addition, 600 to 1,200 sq ft | $300,000 to $800,000 |
| Kitchen renovation on the floor below, mid-range | $40,000 to $75,000, on top of the storey |
| Permit drawings for an addition | $6,000 to $12,000, drawings only |
Note: these are our ranges, not a quote; your price comes after James sees the house, and the first estimate is free. Drawing prices leave out permit fees, HVAC engineering, truss design, committee of adjustment applications and anything unforeseen.
Where a job lands in the range comes down to the finish level, how much of the main floor gets reworked, and what the old house hides once the roof comes off. Builders' prices for the same storey can sit far apart for the same reason, so compare what each one includes before you compare the totals.
What do second-storey quotes leave out?
The biggest gap is usually the floor you already live on. One RedFlagDeals poster got a $280,000 quote for a storey on a 1,300 sq ft bungalow, then found it left out the main floor; he reckoned the real figure was $400,000 to $450,000 (RedFlagDeals thread). That's one owner's estimate, but the pattern is common.
Going up touches the floor below in four places. The new stair takes a slice out of a main-floor room. Bearing walls and new point loads need beams and posts carried down to footings. Plumbing stacks and ductwork have to run up through finished rooms. And once the roof comes off, ceilings below often get patched or replaced.
Before you compare two second-storey quotes, check each one for these lines:
- An engineering review of the foundation and framing.
- Permit drawings. Ours for an addition are $6,000 to $12,000, and that's drawings only: permit fees, HVAC engineering, truss design, committee of adjustment applications and anything unforeseen are on top.
- A reserve for anything unforeseen once the roof comes off and the walls open.
- Main-floor work: the stair opening, beams, ceiling repair, and moving the furnace or upsizing it.
- Rent if you move out, and 13% HST on the contract.
A quote that looks much cheaper than the next one often isn't. It just stops at the top of the new subfloor.
What do permits and fees add in Durham Region?
Municipal fees are small next to construction, but they vary by town and they're easy to calculate yourself. Durham towns charge the building permit by square metre of new floor area, and an 800 sq ft storey is about 74.3 m².
Here is the permit for an 800 sq ft second storey in each town, with the minor variance fee if your plan needs one:
| Town | 2026 rate for new floor area | Permit for 800 sq ft (calculated) | Minor variance fee, if needed |
|---|---|---|---|
| Whitby | $22.37/m² (Schedule N) | $1,663 | $1,526, plus CLOCA's $930 where CLOCA regulates the lot |
| Oshawa | $15.56/m² (By-law 33-2009) | $1,156 | $856 per lot |
| Ajax | $14.22 per unit of floor area (Schedule A) | $1,057 | $1,638.90 (2025 rate) |
| Pickering | $20.12/m² new-house rate; no addition line (2026 user fees) | about $1,495 at that rate, plus a refundable $2,379 performance deposit for additions over 60 m² | $2,500 from 1 July 2026 |
| Clarington | $17.73/m² (By-law 2024-006) | $1,318 | $2,280 |
Note: permit figures are calculated from each town's 2026 schedule for 74.3 m² and aren't quotes from the towns; Ajax doesn't print the unit, Pickering prints no addition line, and its schedule also has a $1,000 deposit line for additions, so ask the City which deposit applies.
A variance is where the time goes. Older Whitby R1 to R3 zones cap height at 8.5 m, and a second storey on a raised bungalow can bump into that. Our guide on whether to build up or out sets out the height and lot coverage limits town by town.
Development charges don't apply. Section 2(3) of the Development Charges Act says a permit whose only effect is to enlarge an existing home doesn't trigger them. That changes if the new floor holds a separate unit, so ask the building department before you draw a kitchen upstairs.
How long does a second-storey addition take?
Plan on most of a year from first drawing to moving back into a finished house. Our Greenwood job, a rear extension plus a new top storey, took 10 months including design, permits and construction. A minor variance adds time on top, because the building permit usually waits until the Committee of Adjustment's decision is final.
Under the Ontario Building Code, a town has 10 business days to decide a permit for a house where no unit sits above another, counted from a complete application (2024 Building Code Compendium). The clock doesn't start until the application is complete, and record volumes slow some towns down. Oshawa's permit page says "we cannot guarantee review timeframes will be met" (Oshawa's building permit page).
Most families move out for at least part of the job. The roof comes off, the stair goes in through the main floor, and one Houzz reply put it bluntly: "your whole house will be a mess" (Houzz discussion). Price rent into the comparison, especially if you're weighing the storey against selling. Our add on or move guide runs those numbers.
Can a second storey get HST relief?
Possibly, but not on its own. The CRA's owner-built rebate list covers owners who renovated the existing house and built a major addition, and its example is "a full second story to an existing bungalow" (CRA new housing rebate page). So a full second storey that at least doubles the living space, together with a renovation of the existing house, can count for the owner-built rebates. A sunroom, family room or bedroom addition by itself doesn't.
The rules, dates and value caps are in our HST relief guide. Confirm with the CRA before you count any rebate in the budget.
How we approach second storeys at Jarvis
We're a family design-build firm based in Ajax. Ceara Jarvis designs through her studio, Juliette Interiors, and James Jarvis runs construction. Because one team prices, draws and builds the job, the stair, the beams and the main-floor work are in the price from the start, so the quote you see covers the house you'll live in, not just the new floor. Our contracts are fixed price: the whole project is priced and the contract signed, with a 10% deposit, before design begins, and any change goes through a change order you sign.
The closest finished example is Greenwood, in east Toronto, roughly 30 km west of our Ajax office. It was a rear extension plus a new top storey with a primary suite, a wet room with a skylight and a den with a walkout balcony, the basement enlarged by removing a brick wall, and full interior design. It took 10 months, including design, permits and construction.
If you're pricing a second floor in Durham, start with our second-storey additions page or read how design-build handles drawings and pricing together.
Questions
How much does a second storey on a bungalow cost in Ontario?
We price a second storey of 600 to 1,200 sq ft on an Ontario bungalow at $300,000 to $800,000 before HST in 2026. Work on the main floor below, such as a new kitchen or bathrooms, adds to that.
That's our range, not a quote. Your price comes after James sees the house, and the first estimate is free.
Why do second-storey addition prices vary so much?
Second-storey prices vary because each builder counts different things. Some ranges include design, engineering, permits and main-floor work; others stop at the new floor. Finish level and the state of the existing house matter too, which is why our own range for 600 to 1,200 sq ft runs from $300,000 to $800,000 before HST.
Do I pay development charges on a second-storey addition in Ontario?
No, not if the second storey only enlarges your existing home. The Development Charges Act excludes work whose only effect is to enlarge an existing residential unit, as of October 2026. If the new floor creates a separate dwelling unit, different rules apply, so confirm with your town's building department.
What does a building permit for a second storey cost in Durham Region?
A building permit for an 800 sq ft second storey costs about $1,057 in Ajax, $1,156 in Oshawa, $1,318 in Clarington and $1,663 in Whitby, calculated from each town's 2026 fee schedule. Pickering prints no addition line; at its new-house rate the fee would be about $1,495, plus a refundable performance deposit of $2,379 (the schedule also lists a $1,000 deposit for additions, so ask the City which applies).
Can we live at home during a second-storey addition?
Living at home during a second-storey addition is hard for most families, because the roof comes off and the new stair cuts into the main floor. Many move out for at least part of the build. Our Greenwood job took 10 months including design and permits, so budget rent for the construction part of that time.
Can my house hold a second storey?
Whether a house can hold a second storey depends on its foundation, its framing and the zoning height limit. An engineer checks the first two, and that study comes before design. The town's zoning by-law sets the height, which is 8.5 m in Whitby's older R1 to R3 zones as of October 2026.
Sources
- Town of Whitby's 2026 fee schedule media-003-ca.cdn.govstack.com
- Development Charges Act ontario.ca
- RedFlagDeals thread forums.redflagdeals.com
- $1,526 media-003-ca.cdn.govstack.com
- By-law 33-2009 media-002-ca.cdn.govstack.com
- $856 per lot oshawa.ca
- Schedule A ajax.ca
- $1,638.90 ajax.ca
- 2026 user fees corporate.pickering.ca
- By-law 2024-006 weblink.clarington.net
- $2,280 weblink.clarington.net
- 2024 Building Code Compendium publications.gov.on.ca
- Oshawa's building permit page oshawa.ca
- Houzz discussion houzz.com
- CRA new housing rebate page canada.ca