Century homes in Ontario
Century homes are the best-built and worst-behaved houses in Ontario. Here is what a real renovation costs, which surprises to budget for, and what is genuinely worth saving.
Quick answer
Renovating a century home in Ontario typically costs $200 to $400 per square foot, against $150 to $300 for a comparable post-war house. The premium comes from what is behind the walls: knob and tube wiring, no insulation, rubble foundations, plaster, and asbestos. Budget a 20 percent contingency, because in a century home the surprises are not a possibility, they are the plan.
$200 to $400
Per sq ft
20%
Contingency, minimum
Pre-1920
What counts
Order matters
Envelope, then finishes
How much does a century home renovation cost?
A century home in Ontario means something specific: built before roughly 1920, usually brick, usually balloon framed, with a rubble or stone foundation and no insulation anywhere in it. They were built by people who expected them to last, out of materials nobody would pay for today. They are also full of a hundred years of other people’s decisions.
| Scope | Typical cost |
|---|---|
| Cosmetic refresh: paint, floors, fixtures | $60 to $120 per sq ft |
| Kitchen and bathrooms, services left alone | $100 to $200 per sq ft |
| Full gut with rewire, plumbing, and insulation | $200 to $400 per sq ft |
| Gut plus underpinning and structural work | $350 to $550 per sq ft |
| Contingency for the unknown | 15 to 25 percent of the above |
The per-square-foot premium over a post-war house is roughly 30 to 40 percent for equivalent work. That is not contractors charging more for charm. It is that almost nothing is square, standard, or where the drawings say.
The five surprises, and what they cost
These are not edge cases. On a pre-1920 house, expect most of them:
- Knob and tube wiring. Rewiring runs $15,000 to $40,000 in a plaster house, and your insurer will likely force the issue regardless of your plans. See our knob and tube guide.
- Nothing is insulated. Solid masonry walls have no cavity to fill, so insulating means building an interior assembly and losing floor area, or accepting a warmer-but-not-warm house. This is the decision that most often surprises people.
- Asbestos and lead. Vermiculite in the attic, asbestos in pipe wrap, duct tape, floor tile and plaster; lead in paint and sometimes in the water service. Testing is cheap. Abatement is not, at $3,000 to $20,000, and it must be done by licensed people under Ontario regulation.
- Balloon framing. The studs run continuously from foundation to roof, so wall cavities are open chimneys for fire. Fire blocking is required when walls are opened, and it is not optional.
- The foundation. Rubble or fieldstone laid without mortar in places, six-foot ceilings, and no weeping tile. See underpinning and waterproofing.
Test for asbestos before demolition, not during. Once a crew has swung a hammer into
vermiculite or asbestos plaster, you have a contaminated site and a far more expensive problem than the test
would have been. A few hundred dollars of sampling is the cheapest insurance in the whole project.
What is worth keeping
The reason to buy a century home is the things nobody builds anymore. Keep them:
- Original trim, baseboards, and casings. Old growth, tight grain, profiles that cost a fortune to reproduce. Strip and reuse.
- Solid wood doors and their hardware. Mortise locks and cast hardware are worth restoring.
- Original windows, sometimes. A sound wood sash with a good storm can outperform a cheap replacement and will last another fifty years. See our window guide for when replacement is genuinely warranted.
- Plaster, where it is sound. It is denser than drywall, quieter, and repairable.
- Brick and stone. Repoint with lime mortar, never Portland cement. Hard modern mortar traps moisture and destroys soft old brick from the inside. This is the most common and most expensive mistake made on Ontario century homes.
What to let go: the wiring, the plumbing, the furnace, the rubble foundation waterproofing, and any 1970s “improvement” that covered something original.
Century homes, done properly
We have been renovating Ontario's older housing stock for two decades. Test first, sequence right. Get a quote.
Talk to ZeybekDo heritage rules apply to your house?
Not every old house is a heritage property, and the distinction matters:
- Listed on a municipal heritage register: generally no restrictions on renovation, but notice is usually required before demolition.
- Designated under Part IV of the Ontario Heritage Act: alterations to the protected attributes need a heritage permit from council, which is a real process with real timelines.
- Heritage Conservation District under Part V: the district’s own plan governs, often covering anything visible from the street, including windows, doors, and paint.
Check the status before you design, not after. A designated property discovered late can invalidate a set of drawings and several months of planning. Our permit guide covers the rest of the approvals.
The right order
Century homes punish work done out of sequence, because everything is connected:
- Test for asbestos and lead. Before anything.
- Water: roof, grading, downspouts, foundation. A wet house rots whatever you install in it.
- Structure: foundation, framing repairs, underpinning if you are doing it.
- Services: rewire, replumb, ducts, while the walls are open. This is the moment. It never gets cheaper.
- Envelope: air sealing and insulation, then heating sized for the house you now have.
- Finishes: plaster, trim, floors, and everything you actually wanted in the first place.
The temptation is always to start at step six, because that is the part you can see. Every century home disaster we have been called into started with a beautiful kitchen installed above a wet basement and beside century-old wiring.
Frequently asked questions
How much does it cost to renovate a century home in Ontario?
Roughly $200 to $400 per square foot for a full gut with rewiring, plumbing, and insulation, against $150 to $300 for a comparable post-war house. Add a 15 to 25 percent contingency, because surprises are the norm rather than the exception.
What are the biggest hidden costs in a century home?
Knob and tube rewiring, asbestos and lead abatement, the absence of any insulation in solid masonry walls, fire blocking required by balloon framing, and rubble foundations with no weeping tile. Most pre-1920 Ontario homes have several of these.
Should I replace the original windows in a century home?
Not automatically. A sound wood sash with a good storm window can outperform a cheap replacement and last another fifty years. Replace when the frames are rotten or out of square, not simply because the glass is old.
Can I renovate a heritage designated home?
Yes, but alterations to the protected heritage attributes require a heritage permit from your municipality. Being listed on a register is different from being designated, and a Heritage Conservation District has its own rules. Confirm your status before you commission drawings.
Is it cheaper to renovate a century home or build new?
Building new is often cheaper per square foot. People renovate century homes for the location, the craftsmanship, and materials that are no longer available at any price. It is rarely the economical choice, and that is fine as long as you go in knowing it.
Zeybek Construction
General contractors, Ontario
Written by the Zeybek team from more than two decades of renovation and construction work across Ontario, from Toronto and the GTA to Kitchener, Waterloo, and beyond. We build kitchens, bathrooms, whole homes, additions, and commercial spaces, and we handle permits and inspections as part of the job.
Related guides
Last updated July 16, 2026. This guide is general information for Ontario homeowners and is not a substitute for a site-specific quote or municipal advice. Costs, rebate programs, and rules vary by municipality and change over time.
Century homes, done properly
We have been renovating Ontario's older housing stock for two decades. Test first, sequence right. Get a quote.