Ontario's Plain-English Guide to Custom Home Buildingπ 705-533-1633 | βοΈ 1-866-868-6606 | βοΈ info@icfhome.ca
Major Remodelling and Renovations in Ontario: What We Take On, What It Costs, and When Rebuilding Beats Renovating
Renovations and suites Major renovations From a builder
Major Remodelling and Renovations in Ontario: What We Take On, What It Costs, and When Rebuilding Beats Renovating
We have been renovating Ontario houses for as long as we have been building them, which is long enough to know that the two hardest words in the trade are “while we are at it”. Here is what we take on, what it costs in 2026, and the honest conversation about when the house you love should become the house you rebuild.
Short version: We take on gut renovations, additions, structural and foundation work including lifting a cottage onto a new ICF basement, whole-house energy retrofits (insulation, air sealing, windows, heat pumps, radiant floors), basement and garden suites, kitchen and bath makeovers inside a larger job, and aging-in-place changes, with the engineering, permits and inspections carried by us. Major work needs a building permit in Ontario and often a designer’s or engineer’s drawings. In 2026 a gut renovation runs $150 to $300 per square foot, an addition $300 to $500, a new foundation under an existing house $80,000 to $200,000, and a basement suite $90,000 to $180,000. When the renovation passes about 60 to 70 percent of the cost of a new house, or the foundation and the envelope both need replacing, rebuilding usually wins, and a substantial renovation can qualify for the HST new housing rebate.
What we take on
- Gut renovations: down to the studs, new everything, the house you wanted in the footprint you have.
- Additions: up, out or over the garage, tied into the existing structure and envelope properly.
- Structural and foundation work: beam replacements, opening up bearing walls, foundation reinforcement and replacement, and lifting a cottage or house to put a new ICF basement under it. Raising a cottage onto an ICF foundation is the one people ask about most.
- Energy retrofits: air sealing, attic and wall insulation, windows, heat pumps, radiant floors added to an existing house, HRVs. Insulating a house in Ontario is the sequence.
- Basement and garden suites: legal second units with the egress, fire separation and ceiling height the Code wants. Legal basement apartment requirements and garden suites in Ontario.
- Kitchen and bath makeovers inside a larger job; we are not the right call for a kitchen on its own.
- Aging-in-place: zero-step entries, main-floor bedrooms and baths, curbless showers, wider doors. Accessible design.
- Cottages: converting seasonal to year-round, which is a foundation, an envelope and a mechanical conversation. Year-round vs seasonal cottage.
What it costs in 2026
| Job | Simcoe County and Georgian Bay range | Notes |
|---|---|---|
| Gut renovation, keeping structure and foundation | $150 to $300 per sq ft | Finishes decide the top end; surprises behind the walls decide the contingency |
| Addition | $300 to $500 per sq ft | Foundation, roof tie-in and matching the envelope; small additions cost more per foot |
| Second storey addition | $350 to $550 per sq ft | Structure, stair, temporary roof, living elsewhere for months |
| New foundation under an existing house (lift, build, set down) | $80,000 to $200,000 | Depends on access, soil, size and whether it becomes a full basement |
| Legal basement suite | $90,000 to $180,000 | Egress, fire separation, kitchen, bath, separate entrance |
| Whole-house energy retrofit (air seal, insulation, windows, heat pump) | $50,000 to $150,000 | Rebates apply; the Home Renovation Savings Program changes often |
| Kitchen or bath inside a larger job | $40,000 to $120,000 / $20,000 to $60,000 | See countertops and kitchen layouts |
Every renovation carries a bigger contingency than a new build, 15 to 25 percent, because the walls have not been opened yet. The contingency explains why, and the renovate vs rebuild calculator runs your numbers.
Permits and the law
Structural changes, additions, new or altered plumbing and HVAC, second units, foundation work, and most changes to the envelope need a building permit in Ontario; paint, flooring and cabinets do not. We pull the permit, carry the engineering and the drawings, and meet the inspector at every stage. Renovation contracts fall under the Consumer Protection Act (a written contract, a ten-day cooling-off period on contracts signed at your home, a ten percent cap on going over the estimate) and the Construction Act holdback applies. Do I need a permit? and what a good contract includes are the two to read before signing anything, with anyone.
Renovate or rebuild
The honest rule: when the renovation passes about 60 to 70 percent of the cost of a new house on the same lot, or when both the foundation and the envelope need replacing, a rebuild usually gives a better house for the money, and a substantial renovation (90 percent or more of the interior gutted) can qualify for the same HST new housing rebate a new house gets. Older cottages on block piers, houses with wet basements and knob-and-tube, and anything where the plan you want does not fit the walls you have are the usual rebuild candidates. Character houses with good bones, a sound foundation and a plan that works are the usual renovations. Tear down and rebuild a cottage and the HST rebate calculator cover the money; we will give you both numbers before you decide.
How we do it
- A walk-through and an honest conversation about what is working, what is not, and whether the house is worth it.
- Drawings and engineering where the structure changes; a specification for everything else, so the quote means something.
- A fixed price or a cost-plus contract with a written contingency, a schedule, and the holdback.
- Opening the walls first where the risk is, before the price is final.
- The permit, the inspections, and the dust control, because you may be living in it.
- The finish, done to the same standard as a new house.
Related guides on this site
Sources and further reading
Questions people ask
Is it cheaper to renovate or rebuild?
Renovating is cheaper until it is not: past about 60 to 70 percent of the cost of a new house, or when the foundation and the envelope both need replacing, a rebuild usually gives a better house for the money and may qualify for the HST new housing rebate.
Do major renovations need a permit in Ontario?
Yes for structural changes, additions, foundation work, new or altered plumbing and HVAC, second units and most envelope changes. Paint, flooring and cabinets do not. The builder pulls the permit and meets the inspector at each stage.
Is there an HST rebate on a major renovation?
A substantial renovation, where 90 percent or more of the interior is removed or replaced, can qualify for the HST new housing rebate on the same terms as a new house; smaller renovations do not.
What does a major renovation cost in Ontario in 2026?
Roughly $150 to $300 per square foot for a gut renovation, $300 to $500 for an addition, $80,000 to $200,000 for a new foundation under an existing house, and $90,000 to $180,000 for a legal basement suite, with a 15 to 25 percent contingency.
Building in Simcoe County or on Georgian Bay?
We are ICFhome.ca, a family builder in Tiny Township with 45 years of custom homes behind us. Pick the path that matches where you are.
Reviewed and updated October 2026. Costs are Ontario ranges, not quotes; code references are to the Ontario Building Code in force at that date.
