---
title: "Is it cheaper to build up or out? 2026 Ontario costs"
url: "https://www.jarviscontracting.ca/guides/build-up-or-out"
description: "Our 2026 ranges: $300,000 to $800,000 to build up a storey, $180,000 to $450,000 for a rear addition. Your lot decides: Durham height and coverage limits."
publisher: "Jarvis Contracting"
dateModified: "2026-10-13"
---
# Is it cheaper to build up or out? 2026 Ontario costs

By Jarvis Contracting. Published 2026-10-05, updated 2026-10-13.

Neither is cheaper every time. We price a second storey of 600 to 1,200 sq ft at $300,000 to $800,000 before HST in 2026. A single-storey rear addition of 300 to 700 sq ft is $180,000 to $450,000, so the two ranges overlap. What tips it is your lot and your foundation, and in Durham Region, Ontario, the zoning limits on height and lot coverage, as of October 2026.

## Key takeaways

- We price a second storey of 600 to 1,200 sq ft at $300,000 to $800,000 before HST in 2026, and a single-storey rear addition of 300 to 700 sq ft at $180,000 to $450,000.
- Small additions cost the most per foot: our 2026 range for a 100 to 300 sq ft bump-out still starts at $60,000. Drawings, a permit and a foundation cost about the same at any size.
- Whitby's older R1 to R3 zones cap lot coverage at 20% and require a 6.0 m rear yard under Schedule A of [Zoning By-law 1784](https://media-003-ca.cdn.govstack.com/whitby-ca/media/orfb0rfx/1784_zoning-by-law_2025_consolidation-accessible.pdf), which often rules out building far back.
- Height limits in common older Durham zones run from 8.5 m in Whitby to 11.0 m in Ajax, per each town's zoning by-law, such as [Ajax's Section 6 zone table](https://ajax.ca/wp-content/uploads/2026/04/6-Section-6-Zone-Provisions_2026-March-Consolidation-Final.pdf).
- The CRA's example of a major addition for its owner-built HST rebates is "a full second story to an existing bungalow" ([CRA new housing rebate page](https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/gst-hst-businesses/gst-hst-rebates/new-housing-rebate.html)). That can tilt the tax picture toward going up.

## Is it cheaper to build up or out in Ontario?

On price alone, our ranges for the two overlap too much to call. On total cost, it depends on how much space you need. Going out is usually the better deal for a modest room on a lot with space behind the house. Going up is usually the better deal when you need a whole floor of bedrooms and the lot has no room left.

Size is the hidden variable. Every addition carries fixed costs that barely change with its size: drawings, a permit, an engineer, getting crews and machines to site, tying the new roof or floor into the old house. Spread over a 100 to 300 sq ft bump-out, those costs are why our range for one starts at $60,000. Spread over a full floor, they weigh far less on each square foot. That's why a second storey can be cheaper per foot than a small rear addition, even though it's the bigger, harder job.

So the useful comparison isn't up versus out at the same size. It's the right-sized version of each. A family room off the kitchen and a three-bedroom floor upstairs aren't competing for the same job.

## What does each option pay for that the other doesn't?

Each direction carries costs the other skips, and they're the lines that end up deciding most jobs.

Here is where the money goes in each case:

| Cost driver | Building up | Building out |
|---|---|---|
| Foundation | uses the existing one, if it can carry the load; may need footings under new posts | new footings and walls, with a crawl space, slab or full basement |
| Engineering check | foundation and framing review by an engineer | soils and footing design, usually simpler |
| Roof | old roof comes off and a new one goes on top | old roof stays; new roof ties into it |
| Main floor | loses space to a new stair; plumbing and ducts run up through it | loses a wall or window where the opening goes |
| Lot space | none used | eats into yard and lot coverage |
| Living at home | hard while the roof is off | often possible until the tie-in |
| Conservation authority | rarely triggered | a CLOCA or TRCA permit if the footprint grows into a regulated area |

Note: this is a list of what each option pays for, not a price list; your drawings decide the figures.

Two lines carry most of the risk. Going up, it's the foundation: if the engineer finds the footings can't take a second floor, the cost jumps, which is why the study comes first. Going out, it's the lot: if zoning or a conservation authority says no to the footprint, the plan stops at a variance hearing or doesn't happen.

## What do Durham zoning limits allow in each direction?

Zoning decides a lot of up-or-out questions before cost does. Height limits cap how far up you can go, and lot coverage and yard setbacks cap how far out.

Here are the limits in the common older residential zones of each Durham town, as of October 2026:

| Town | Zone | Maximum height | Maximum lot coverage | Minor variance fee |
|---|---|---|---|---|
| Whitby | R1 to R3, By-law 1784 | 8.5 m | 20% | [$1,526](https://media-003-ca.cdn.govstack.com/whitby-ca/media/txxlnw3w/pl-application_minorvariance.pdf) |
| Oshawa | R1-A to R1-E, By-law 60-94 | 9.0 m | 40% (45% with an accessory apartment) | [$856 per lot](https://www.oshawa.ca/business-development/planning-and-development/development-applications/committee-of-adjustment/) |
| Ajax | R1 and R2, By-law 95-2003 | 11.0 m | 30% (R1-A), 33% (R1-B), 45% (R1-C to R1-F); 45% on any lot with an accessory unit | [$1,638.90](https://ajax.ca/wp-content/uploads/2026/03/By-law-61-2024-2025-User-Fees-By-law.pdf) (2025 rate) |
| Pickering | R1D and R1E, By-law 8149/24 | 9.0 m | 33% | [$2,500](https://corporate.pickering.ca/WebLink/DocView.aspx?id=261891&dbid=0&repo=PICKERING) from 1 July 2026 |
| Clarington | R1, By-law 84-63 | 10.5 m | 40%; 25% to 35% in Bowmanville's Neighbourhood Character Overlay | [$2,280](https://weblink.clarington.net/WebLink/ElectronicFile.aspx?docid=455554&dbid=0&repo=Clarington) |

Note: limits are from each zoning by-law ([Whitby](https://media-003-ca.cdn.govstack.com/whitby-ca/media/orfb0rfx/1784_zoning-by-law_2025_consolidation-accessible.pdf), [Oshawa](https://media-002-ca.cdn.govstack.com/oshawa-016-ca/media/xrthfhqx/zoning-by-law-60-94.pdf), [Ajax](https://ajax.ca/wp-content/uploads/2026/04/6-Section-6-Zone-Provisions_2026-March-Consolidation-Final.pdf), [Pickering](https://corporate.pickering.ca/WebLink/DocView.aspx?id=258309&dbid=1&repo=PICKERING), [Clarington](https://media-003-ca.cdn.govstack.com/clarington-018-ca/media/hq0jc0up/zoning-by-law-84-63-aoda.pdf)) for the zones named, and variance fees from each town's fee schedule; many newer subdivisions have their own zones with different numbers, so check yours.

Whitby is the town where this bites hardest. A 20% coverage cap is tight: on an 835 m2 lot, the smallest serviced interior lot the R3 zone allows, it leaves 167 m2, about 1,800 sq ft, of building footprint (calculated). A bungalow already near that line has little room to go out without a variance. The same zones cap height at 8.5 m, which can pinch a raised bungalow or a steep roof.

Setbacks moved a little in late 2025. Since 21 November 2025, [O. Reg. 545/06](https://www.ontario.ca/laws/regulation/060545) treats urban residential setbacks as 90% of the by-law figure, outside shorelines, valleys, wetlands, railways and the Greenbelt. On Whitby's 6.0 m rear yard, that's 5.4 m (calculated). Ask the building department how it applies to your lot before you rely on it.

Conservation authorities matter more for going out, because they regulate new or larger footprints near valleys, streams and the shoreline. In Whitby, Oshawa and parts of Clarington that's CLOCA, where a Minor Permit B for a minor addition costs $535 and a standard permit starts at $1,990 ([CLOCA's 2026 fee schedule](https://www.cloca.com/_files/ugd/6cdd05_ca1ea5bbdaa34f3ca770f69ab8f830e4.pdf)). Ajax and Pickering fall mostly under TRCA, with CLOCA covering parts of each. A variance in Whitby on CLOCA-regulated land also carries CLOCA's $930 processing fee.

## What about building down instead?

Building down means lowering the basement floor so it's full-height living space. It's the third option when the lot is full and the height limit is close. It isn't cheap: we price underpinning the full perimeter at $60,000 to $120,000 before HST in 2026. That buys height, not footprint, and the space is below grade. Our guide on [legal basement apartment costs](https://www.jarviscontracting.ca/guides/legal-basement-apartment-cost-ontario) covers what it takes to finish it as a unit.

## Does going up or out change the HST picture?

It can, but size is what counts, not direction. The CRA's owner-built rebates can apply when you renovate the existing house and build a major addition, and its example is "a full second story to an existing bungalow" ([CRA new housing rebate page](https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/gst-hst-businesses/gst-hst-rebates/new-housing-rebate.html)). An addition that at least doubles the living space, together with a renovation of the existing house, may qualify. A sunroom, family room or bedroom addition by itself doesn't. In practice, that favours the full second storey. See the [HST relief guide](https://www.jarviscontracting.ca/guides/ontario-hst-relief-substantial-renovation) and confirm with the CRA before you count on it.

## How we decide between up and out at Jarvis

We start with the lot and the foundation, not the wish list. Ceara Jarvis designs through her studio, Juliette Interiors, James Jarvis runs construction, and we draw the permit set in-house, so we can weigh both directions against your zoning and price the one that fits. The ranges on this page are ours for 2026; your price comes after James sees the house and the lot, and the first estimate is free.

Sometimes the answer is both. Our [Greenwood](https://www.jarviscontracting.ca/projects/greenwood) project in east Toronto, roughly 30 km west of our Ajax office, paired a rear extension with a new top storey holding a primary suite, a wet room with a skylight and a den with a walkout balcony, and enlarged the basement by removing a brick wall. It took 10 months, including design, permits and construction.

For the cost detail behind each direction, read [what a second-storey addition costs](https://www.jarviscontracting.ca/guides/second-storey-addition-cost-ontario) and [what a home addition costs](https://www.jarviscontracting.ca/guides/home-addition-cost-ontario). If you're also weighing a move, see [add on or move](https://www.jarviscontracting.ca/guides/renovate-or-move). Our [home additions](https://www.jarviscontracting.ca/home-additions) and [second-storey additions](https://www.jarviscontracting.ca/second-storey-additions) pages show how we work in Durham.

## Questions

### Is it cheaper to build up or out in Ontario?

Whether it's cheaper to build up or out in Ontario depends on how much space you need and what your lot allows. Our 2026 ranges overlap: $300,000 to $800,000 for a 600 to 1,200 sq ft second storey against $180,000 to $450,000 for a 300 to 700 sq ft rear addition, before HST. Small additions cost the most per foot, so a modest room favours going out and a full floor of bedrooms often favours going up.

### Does a second storey need a new foundation?

A second storey doesn't always need a new foundation, but the existing one has to carry the extra load, and only an engineer can say whether it will. If the footings fall short, they need work before anything goes up, so the study comes before design.

### How much of my lot can I cover in Whitby?

In Whitby's older R1, R2 and R3 zones, buildings can cover up to 20% of the lot under Schedule A of Zoning By-law 1784, as of October 2026. Many newer Whitby subdivisions have their own zones with different limits, so check the zoning map for your address before you plan to build out.

### How tall can a house be in Durham Region?

A house in the common older residential zones of Durham Region can be 8.5 m tall in Whitby, 9.0 m in Oshawa and Pickering, 10.5 m in Clarington and 11.0 m in Ajax, as of October 2026. Newer zones often differ, and going over the limit needs a minor variance from the Committee of Adjustment.

### Can we stay in the house while building out?

Staying in the house is usually easier with a ground-floor addition than with a second storey, because the old roof stays on and the main house stays closed until the opening is cut. With a second storey the roof comes off, so most families move out for part of the job.

### Is a small bump-out worth it compared with a bigger addition?

A small bump-out costs more per square foot than a bigger addition, because drawings, permits and foundation work cost about the same either way. Our 2026 range for a 100 to 300 sq ft bump-out is $60,000 to $180,000 before HST. It can still be worth it when a few feet fix a cramped kitchen.