Family owned since 2007Ajax · Durham Region · Greater Toronto Area4.9 on Google
What’s your next chapter?

Good homes start
with a conversation.

james@jarviscontracting.ca(289) 892-4169Home additions & renovations
Durham Region & the Greater Toronto Area
A narrow kitchen with a walnut island, cream shaker cabinets and a herringbone floor, beside an open oak stair with looped black balusters

Our expertise

Home additions

Rear, side and garage additions, designed and built by one team so the new rooms look like they were always part of the house.

Let’s talk about your home
Explore

We price a home addition in the Greater Toronto Area (GTA) at about $350 to $600 per square foot in 2026, and a single-storey rear addition of 300 to 700 sq ft at about $180,000 to $450,000, before HST. We design the addition, draw the permit set and build it, from our office in Ajax across Durham Region, Ontario and the GTA.

What's included

A dining nook with an upholstered banquette, a fluted black round table, two velvet chairs and glass-front cabinets on either side

Every job, start to finish

  1. A site visit and measurements
  2. Floor plans and a 3D model of the new rooms
  3. Permit drawings, with structural engineering wherever loads change
  4. The permit application, and any minor variance
  5. Foundations, framing, the roof tie-in and exterior finishes
  6. Interior finishes chosen with our designer
  7. One point of contact from the first visit to handover

The kinds of job

  • Rear and side extensions
  • Room additions and sunrooms
  • In-law suites
  • Garage additions and conversions
  • Main-floor work in the same job
Typical duration
Greenwood, a rear extension and a new top floor in Toronto, took 10 months including the permit, the design and construction.
Permits involved
  • A building permit from your municipality before work starts (Building Code Act, s. 8)
  • A minor variance from the Committee of Adjustment when the design breaks a zoning limit such as a setback, height or lot coverage
  • A conservation authority permit when the lot is in a regulated area near a stream, wetland or shoreline (Ontario Regulation 41/24)
  • A heritage permit for exterior work in a Heritage Conservation District (Ontario Heritage Act, Part V)
  • No development charges: enlarging an existing home doesn't trigger them (Development Charges Act, 1997)

What it costs

Our 2026 ranges, not quotes. Every job is priced after a site visit, and the first estimate is free.

WorkRangeBasisSource
Home addition, any type$350 to $600per sq ftGTA, 2026. Before 13% HST.Our 2026 price
Single-storey rear addition, 300 to 700 sq ft$180,000 to $450,000GTA, 2026. Before 13% HST.Our 2026 price
Bump-out, 100 to 300 sq ft$60,000 to $180,000GTA, 2026. Before 13% HST.Our 2026 price

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

Finished jobs

Home additions

Is it cheaper to build up or out?

It depends on what's underneath. Building out needs a new foundation; building up needs a foundation and walls strong enough to carry another floor, which a structural engineer checks before anything is drawn. Our guide to building up or out walks through both.

Do I need a permit for an addition in Ontario?

Yes. Every addition needs a building permit from the municipality before work starts (Building Code Act, s. 8), and as of October 2026 plans are reviewed under the 2024 Ontario Building Code, in force since 1 January 2025 (O. Reg. 163/24). If the addition breaks a zoning limit you also need a minor variance from the Committee of Adjustment. Since 21 November 2025, minimum setbacks on urban residential lots count as 90% of the zoning figure (Ontario regulation), which sometimes removes the need for one.

Does an addition pay development charges?

No. Enlarging an existing home doesn't trigger development charges under the Development Charges Act. You pay the permit fee: in Whitby, $22.37 per square metre of new floor area in 2026 (Town of Whitby fee schedule).

Is it cheaper to add on or move?

Moving has its own price before you spend a dollar on space: land transfer tax, commission, legal fees and the move itself. Toronto buyers pay a municipal land transfer tax on top of the provincial one; Durham buyers pay the provincial tax only (ontario.ca). Our renovate or move guide does the arithmetic.

How long does an addition take?

Greenwood, a rear extension and a new top floor on a Toronto house, took 10 months from the permit and the design through construction. A smaller single-storey addition takes less; we give you a schedule with the contract.

Real work

Greenwood added a primary suite, a wet room under a skylight and a den with a balcony on a new top floor, plus a rear extension, and enlarged the basement by taking out a brick wall. That last change needed new engineering and a permit amendment, and cost us a short delay. See it in our projects.

Where we do this

In Ajax, Aurora, Brampton, Brock, Burlington, Caledon, Clarington, East Gwillimbury, Georgina, Halton Hills, King, Markham, Milton, Mississauga, Newmarket, Oakville, Oshawa, Pickering, Richmond Hill, Scarborough, Scugog, Toronto, Uxbridge, Vaughan, Whitby and Whitchurch-Stouffville.

How the job runs

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Inspections

    The municipal building inspector checks the work at each stage the permit sets, before it gets covered up.

  10. 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

Jarvis Contracting Inc. BBB Business ReviewBBB ratingA+View profile ↗

Questions

Do I need a permit for a home addition in Ontario?

Yes. Any home addition in Ontario needs a building permit from your municipality before work starts, under section 8 of the Building Code Act. If the addition breaks a zoning limit, such as a setback or lot coverage, you also need a minor variance from the Committee of Adjustment first. We draw the plans and make both applications.

How much does a home addition cost in the GTA?

We price GTA home additions at about $350 to $600 per square foot in 2026, and a single-storey rear addition of 300 to 700 sq ft at $180,000 to $450,000, before 13% HST. The foundation, the structural work and the finishes move the number most. We price your addition after a site visit.

Do home additions pay development charges in Ontario?

No. Ontario's Development Charges Act says enlarging an existing home doesn't trigger development charges, so a rear addition or a second storey pays the building permit fee but no development charges. Adding a second or third unit within the provincial limits is exempt too.

Does a home addition need an HCRA licence or a Tarion warranty?

No. The Home Construction Regulatory Authority licenses builders of new homes, and it says renovating or adding to an existing home doesn't make it a new home. So an addition needs no HCRA licence and Tarion's new-home warranty doesn't cover it. Your protection is the written contract Ontario requires for any renovation over $50.

Will the addition match the rest of the house?

A home addition should look like it was always there, and that starts in the drawings: rooflines, floor heights and finishes are drawn with the existing house. On our West Lynde job the drawn roof tie-in would have left low spots for water, so we built one single-slope roof instead.

Guides

Sources

  1. Building Code Act, s. 8 ontario.ca
  2. O. Reg. 163/24 ontario.ca
  3. Ontario regulation ontario.ca
  4. Development Charges Act ontario.ca
  5. Town of Whitby fee schedule media-003-ca.cdn.govstack.com
  6. ontario.ca ontario.ca