Durham Region
Home additions in Oshawa
Oshawa home additions as of October 2026: 40% or 45% lot coverage, 7.5 m rear yards, Ontario's 90% setback rule, the $856 variance and airport clearance.
How far can I build an addition out the back of my Oshawa house before I need a variance?
In Oshawa's R1-A to R1-E zones the house can cover 40% of the lot (45% with an accessory apartment) and must keep a 7.5 m rear yard, which Ontario has deemed to be 6.75 m since 21 November 2025. Past those lines you apply to the City of Oshawa Committee of Adjustment, at $856 per lot as of October 2026.
Key takeaways
- Houses on R1-A to R1-E lots in Oshawa may cover 40% of the lot, or 45% with an accessory apartment and city water and sewer, per the zone table in Zoning By-law 60-94.
- The minimum rear yard in those Oshawa zones is 7.5 m and the minimum interior side yard is 1.2 m, per Table 6.2.
- Since 21 November 2025, Ontario Regulation 545/06 deems most urban minimum setbacks to be 90% of the by-law figure, which turns Oshawa's 7.5 m rear yard into 6.75 m.
- A minor variance for a house costs $856 per lot at the City of Oshawa Committee of Adjustment, and double that if the work is already built.
- An addition that creates no new unit pays no development charges under the Development Charges Act, against the $130,682 Oshawa lists for a new house.
Permits in Oshawa
What applies to home additions here, with the municipal source for each line.
| Item | What applies | Source |
|---|---|---|
| Where to apply | Oshawa Application Portal (servicecv.oshawa.ca) | oshawa.caChecked 5 October 2026In the source's wordsYou can now apply for building permits, check the status of applications and pay fees through our Application Portal. |
| Addition permit fee | $15.56 per m² | media-002-ca.cdn.govstack.comChecked 5 October 2026In the source's wordsHouse, Accessory building for human habitation $15.56 / sq. m. |
| Conservation authority | Central Lake Ontario Conservation Authority (CLOCA) | oshawa.caChecked 5 October 2026In the source's wordscontact the Central Lake Ontario Conservation Authority (C.L.O.C.A.) |
| Zoning by-law | Zoning By-law 60-94 (as amended; consolidation updated 12/01/2025) | oshawa.caChecked 5 October 2026In the source's wordsZoning By-law 60-94, as amended, is the City's current zoning by-law. |
| Minor variance (Committee of Adjustment) fee | $856 per lot | oshawa.caChecked 5 October 2026In the source's words$856 |
Fees and rules as published by Oshawa and the agencies linked, checked 6 October 2026. Confirm with the building department before you apply.
The nearest finished jobs
West Lynde
New second storey of about 800 sq ft with two bedrooms, a walk-in closet and a bathroom; new kitchen, two new bathrooms, floors, stairs and trim below.
Explore the home
Greenwood
Top floor replaced with a new storey, rear extension, basement enlarged, full interior design and build.
Explore the home
What it costs
Ranges with their sources, not quotes.
| Work | Range | Basis | Source |
|---|---|---|---|
| Home addition, any type | $350 to $600per sq ft | GTA, 2026. Before 13% HST. | Our 2026 price |
| Single-storey rear addition, 300 to 700 sq ft | $180,000 to $450,000 | GTA, 2026. Before 13% HST. | Our 2026 price |
| Bump-out, 100 to 300 sq ft | $60,000 to $180,000 | GTA, 2026. Before 13% HST. | Our 2026 price |
Our 2026 ranges, not quotes: every job is priced after a site visit.
What moves the number
- The foundation: full basement, crawlspace or slab
- How much of the existing house opens up to join the new space
- The roof: new rafters meeting the old roof
- Engineering, drawings and the permit
- Finish level inside
- 13% HST, which these ranges leave out
Building in Oshawa
How much of my Oshawa lot can the house cover?
Coverage counts every building with a roof: the house, an attached or detached garage and the shed. Oshawa's definition leaves out unenclosed decks and porches, eaves and bay windows. In R1-A to R1-E the cap is 40%. On a 450 m² lot that's 180 m² of footprint in total. Say the house covers 110 m² and a detached garage 25 m²: you have 45 m² left for an addition (our arithmetic).
The footnote to Table 6.2 lifts the cap to 45% when the property has one or more accessory apartments and is on municipal water and sewer. On that same lot, that's another 22.5 m² of footprint. Larger estate lots in R1-F to R1-H work on 10% to 20% instead.
What setbacks does an Oshawa addition have to keep?
The by-law figures for the common R1 zones are these:
| Zone | Front yard | Interior side yard | Rear yard |
|---|---|---|---|
| R1-A | 9.0 m | 1.2 m | 7.5 m |
| R1-B | 6.0 m | 1.2 m | 7.5 m |
| R1-C | 9.0 m (6.0 m in subdivisions registered after 1 January 1987) | 1.2 m | 7.5 m |
| R1-D | 6.0 m | 1.2 m | 7.5 m |
| R1-E | 6.0 m | 1.2 m on one side | 7.5 m |
Note: these are the minimums printed in By-law 60-94 before Ontario's 90% rule. Special zones such as R1-B(1) carry their own numbers.
Ontario's 90% rule makes the working rear yard 6.75 m and the side yard 1.08 m, and the figure in force when your permit issues is locked in. It doesn't apply in the Greenbelt or in the areas listed in O. Reg. 254/23: within 300 m of an active railway, or 120 m of a wetland, shoreline or river valley. There, the full 7.5 m stands. We check your lot against both before we draw a wall.
When does the Committee of Adjustment come in?
The Committee's own page uses a side-yard case as its example: a house 0.9 m from the interior side line where 1.2 m is required. Under the 90% rule the minimum is now 1.08 m, so 0.9 m still needs a variance; 1.1 m would not (our reading). The fee is $856 per lot, capped at $11,414, and the page doesn't say which year that rate is for. Agendas may be limited to 10 applications, first come first served, and 2026 meetings run about every three weeks.
In Oshawa the sequence is fixed: the building permits page says an application that needs Committee of Adjustment approval is premature and won't be processed, so the variance comes first and the permit second.
Who has built this kind of addition?
Our nearest finished addition is West Lynde, about 6 km west in Whitby, where a bungalow went up to two storeys. The nearest rear extension is Greenwood in east Toronto, about 45 km west, with a new top storey as well. Enlarging its basement meant new engineering and a permit amendment, which cost us time. The lesson for an Oshawa addition: get the engineer's answers before the permit goes in.
How the job runs in Oshawa
Meet James
James meets you at the house, hears what you want and gives you a rough estimate on the spot. The first estimate is free.
Proposal and contract
If the estimate works for you, James prepares a detailed proposal. The whole project is priced, and the contract signed with a 10% deposit, before any design work begins.
Design onboarding
Our designer sends you an onboarding email with some homework: your style, how your family uses the house, and what you need and want. You share Pinterest boards, then go through them together on a Zoom call: what you like in the pictures, and what you don't.
Measure and floor plans
The designer measures the house and draws the floor plan: which walls come out, where the stairs land, how new space joins the old. We go through it with you until it's confirmed.
Drawings and 3D rendering
With the plan confirmed, she draws the elevations and the millwork, then puts it all into a 3D rendering, so you see the rooms before anyone orders a cabinet.
Finishes presentation
We don't take you round the stores: there are too many options. Using what she learned in onboarding, the designer narrows the tile, flooring, quartz, plumbing fixtures and the rest to a few choices that suit your style, collects the samples and presents them to you in our office. If a selection changes the price, the change goes through a change order you sign.
Permits and engineering
We prepare the permit drawings, bring in the structural engineer wherever a beam or a load changes, and apply to the municipality. If the plan changes after the permit is issued, we file the amendment. In Oshawa, applications go through the town's online permit portal.
Construction
Our crew and trades build it, with one point of contact from demolition to the last coat of paint. Our site supervisors write a job log every day, which you can follow in our online app. When we open a wall and find a problem, you hear about it, and what it costs, before we fix it.
Inspections
The municipal building inspector checks the work at each stage the permit sets, before it gets covered up. Inspections are booked with Oshawa's building department.
Handover
We walk the finished house with you and put right anything that isn't. On one job a stair stain didn't match the new floor, so we refinished the stairs.
Credentials
- Written warranty1 year workmanship and materials, 2 years plumbing, heating, electrical and building envelope, 7 years structural
- BBB Accredited BusinessAccredited by the Better Business Bureau since November 2025
- Durham Region Home Builders' AssociationMember, Renovators
- RenoMarkRenoMark renovator, through the DRHBA
Questions
Does a home addition in Oshawa pay development charges?
Why would the Oshawa Executive Airport need to clear my addition?
Do I need a CLOCA permit for an addition near a creek in Oshawa?
What does an attached garage addition cost in Oshawa permit fees?
Sources
- City of Oshawa, Zoning By-law 60-94, Table 6.2 media-002-ca.cdn.govstack.com
- City of Oshawa, Committee of Adjustment oshawa.ca
- Ontario Regulation 545/06, deemed setbacks ontario.ca
- City of Oshawa, building permits oshawa.ca
- O. Reg. 254/23 ontario.ca
- City of Oshawa: Bylaw 33 2009 as amended by by law 118 2025 media-002-ca.cdn.govstack.com
- City of Oshawa: Zoning oshawa.ca
How this page was made
Written by Jarvis Contracting from the municipalities' published rules, our 2026 price ranges and the nearest finished jobs.
- Facts checked
- 6 October 2026
- Fact-checked
- Space & Story, 5 October 2026