Fix what a buyer can see or an inspector will flag: leaks, loose rails, tired caulking, sticking doors and missing alarms. Most of these jobs need no building permit in Vaughan or Markham, but Ontario's new carbon monoxide alarm rule does apply.
Thornhill listings compete on condition. Buyers here walk through a lot of similar homes, and small visible problems make a house feel neglected long before anyone opens a wall. The goal before listing isn't a renovation. It's removing the reasons a buyer, or the buyer's inspector, has to knock money off the price. Here's how to sort the jobs worth doing from the ones that aren't, and what the rules actually say.
Start with what a buyer sees in the first ten minutes
Ontario law draws a line between patent defects, which are visible and which you don't have to disclose because a buyer can spot them, and latent defects, which are hidden. That line is a useful checklist. Patent problems are exactly the ones buyers and inspectors find, so they're the ones that cost you in negotiation. The usual list:
- Water: dripping taps, a toilet that runs, stained ceiling spots, cracked or missing caulking around tubs and windows.
- Doors and trim: sticking or misaligned doors, loose handrails and guards, damaged baseboards.
- Walls: nail pops, small cracks, scuffs and old patches that were never painted over.
- Light and power: burnt-out bulbs and dead switches, outlets that don't hold a plug, mismatched fixtures.
- Exterior: loose or rotted deck boards, leaning fence panels, failing exterior caulking, a garage door that scrapes.
None of these is expensive on its own. Together they tell a buyer the house has been deferred. A single visit that clears a whole list is usually a better use of money than one new feature.
The one rule that changed on January 1, 2026: carbon monoxide alarms
Ontario Regulation 87/25 amended the Fire Code so that existing homes with a fuel-burning appliance (a furnace, water heater or gas stove), a fireplace or an attached garage need a carbon monoxide alarm both next to every sleeping area and on every storey, including storeys with no bedroom. The storey requirement is the new part, and it catches a lot of homes that already had an alarm upstairs. In an owner-occupied home, the homeowner is responsible for compliance, and the local fire department enforces it.
The Province's guidance says alarms can be hardwired, battery-operated or plug-in, and that combined smoke and CO units are fine. Look for a recognized testing mark such as CSA, ULC or Intertek. It's a cheap fix, it's checkable by any buyer's inspector, and a missing alarm is the kind of finding that makes people wonder what else was missed. Check the date printed on your existing smoke alarms too, since alarms wear out.
What you have to disclose, and what you don't
Sellers in Ontario must disclose latent defects they know about, meaning hidden problems that affect safety or habitability. The Ontario Real Estate Association's Seller Property Information Statement (SPIS, OREA Form 220) is the standard way to put your answers in writing. It isn't mandatory, and filling it out doesn't by itself protect you if you leave something out, but if you know about past water damage, a wiring issue or a structural problem, saying so is safer than hoping it isn't found.
A small repair doesn't erase a known problem. A fresh coat of paint over a water stain you know the cause of is not a fix, and it can read as concealment. If something underlying is wrong, repair the cause, keep the paperwork, and disclose it. This is general information, not legal advice, so ask your real estate lawyer about anything specific.
Which side of Yonge Street you're on
Between Steeles Avenue and Highway 7, Yonge Street is the boundary between Vaughan and Markham. Thornhill homes west of it are in Vaughan, and homes east of it are in Markham. Your tax bill shows which city you belong to. For the small jobs in this article the two cities' rules line up closely, which is the good news.
- Markham's published list of work that does not need a building permit includes painting and decorating, maintenance and repairs, kitchen or bathroom cupboards, replacing plumbing fixtures or water heaters, replacing windows or doors with no change to the rough opening, replacing roofing or shingles, and fences other than a pool enclosure. It does require a permit for raised decks more than 24 inches above grade, installing any new plumbing piping, and replacing an exterior wall or cladding.
- Vaughan's building permit page likewise exempts replacing existing windows and doors, roofing and existing plumbing fixtures. It requires a permit for a deck or porch 600 mm (about 23 5/8 inches) or more above grade, for a deck of 18.6 m² (about 200 sq ft) or more or one attached to another structure, and for a new or widened window or door opening in an exterior wall.
Two cautions apply on either side. Permit-free work still has to meet the zoning by-law. And electrical work is regulated by the Electrical Safety Authority rather than the city, so "no building permit" doesn't mean anyone can do it; see our guide to checking a contractor's licence.
Unfinished permits are a bigger problem than unfixed taps
If you finished a basement, built a deck or changed plumbing in the past, check whether that work was permitted and closed. Ontario lawyers treat an open building permit as a title issue, because it can leave the buyer exposed to future problems, and it's the kind of thing a buyer's lawyer raises close to closing, when you have the least time. Ask your city's building department what's on file for your address, either Vaughan Building Standards or Markham's building permit desk, well before you list.
What to skip
Don't start a kitchen or bathroom renovation days before listing unless it's already underway. Rushed work shows, and you won't recover what you spend on someone else's taste. Neutral paint, working fixtures and a clean punch list nearly always beat a half-finished upgrade.
Quick answers
What small repairs should I do before listing a house in Thornhill?
Fix what a buyer sees or a home inspector will flag: leaking taps, loose handrails, cracked caulking, sticking doors, burnt-out fixtures and missing alarms. Skip renovations you can't recoup.
Do I have to disclose problems when selling a home in Ontario?
You must disclose hidden defects you know about that affect safety or habitability. Visible defects don't need disclosure. The OREA Seller Property Information Statement is a common way to do it, but it isn't mandatory.
Do I need carbon monoxide alarms to sell my Thornhill home?
If your home has a fuel-burning appliance, fireplace or attached garage, Ontario's Fire Code now requires a CO alarm on every storey and next to bedrooms, since January 1, 2026. The homeowner is responsible.
Do small repairs need a building permit in Vaughan or Markham?
Usually not. Both cities list painting, replacing fixtures, roofing and same-size windows and doors as permit-free. Raised decks, new plumbing piping and cladding replacement do need one.
Which city is my Thornhill home in, Vaughan or Markham?
Yonge Street is the boundary between Steeles Avenue and Highway 7. Homes west of it are in Vaughan and homes east of it are in Markham, so check your tax bill if you're unsure. If you'd rather have the list done in one visit, Rhodex can price it.
Do the list, then stop
Walk through the house like a buyer with a notepad, write down everything you'd notice, fix the small things, check the alarms, and confirm your permit history. That's a better pre-listing plan than any single big project.
Related reading
- How Do Building Permits Actually Work in York Region?
- How Do I Know If a Contractor Is Licensed in Ontario?
- How Rhodex Vets a Craftsman Before They Reach Your Door
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