Repainting the outside of a Thornhill house typically costs about $3.50 to $6 per square foot of wall before HST. Shaded lots under mature trees, old paint and heritage-district streets are what move the price.
Thornhill's older streets have the thing every painter wants and every painter dreads: big, mature trees. They cool the house and they keep the walls damp. If your siding sits in shade for most of the day, the paint on it is working harder than the paint on a sunny new-build street, and a good quote should show it.
What a repaint typically costs
These are general market estimates from public sources, not a quote. One 2026 Ontario cost guide prices two coats of paint at about $3.50 per square foot of wall, before HST, for washing, scraping and spot priming of a normally weathered surface with trim included, assuming two storeys worked from ladders. On that rate, 1,800 square feet of wall comes to roughly $6,300 before HST. HomeStars gives a national range of $3 to $6 per square foot and says Toronto sits at the higher end of it, so a Thornhill budget of about $3.50 to $6 per square foot is a sensible starting point.
Those rates assume a normal weathered surface. The same Ontario guide says stripping to bare wood, lead paint on a house built before 1980 and three-storey walls are quoted on the house, not off a rate sheet. Those are exactly the situations an older Thornhill home can land in.
Why mature trees change the job, not just the schedule
- Mildew and algae. Shaded siding dries slowly after rain and dew, and that moisture is what lets mildew and algae take hold. It shows as dark streaks and a blotchy finish. Painting over it without washing and treating it first just paints over the problem.
- Earlier paint failure. Damp wood trim and siding blister, crack and peel sooner than the same boards on a sunny wall. Expect more scraping, more spot priming and more caulking at joints before the first coat goes on. That is where a shaded house picks up cost.
- Branches in the way. Limbs against the siding or eaves make ladder work slower and trap moisture against the wall. If a tree needs pruning to do the job, check the City of Vaughan or City of Markham tree rules for your lot before anyone cuts. We have not verified the size thresholds for either, so ask the city, not the painter.
- Debris and sap. A fall repaint under maple and oak means leaves landing on wet paint. A painter who schedules around the leaf drop and the forecast is worth more than the cheapest quote.
Check for lead before anyone scrapes
Health Canada says a home built before 1960 probably contains lead-based paint, and that the exterior of a home built between 1960 and 1990 may. A lot of Thornhill's housing stock falls in those years. The same page says leaving intact lead paint alone can be safer than removing it, but that chipping or flaking paint is a serious hazard. It also says not to use sanders, heat guns or blowlamps, because they create toxic dust and fumes, and that scrapings and chips go into a sealed container and are disposed of the way your municipality instructs.
In practice: if your house is older than 1990, ask any painter how they plan to prep before they quote, and have the paint tested if there is any chance it contains lead. A quote that says "sand it all back" on a 1970s exterior should raise a question. This is also the usual reason an older house is quoted on the house instead of by the square foot.
Heritage districts: call before you choose a colour
Thornhill has two heritage conservation districts, one administered by Vaughan and one by Markham. Markham's heritage page says changes to properties in a heritage conservation district, Thornhill among them, require a heritage review and approvals process, lists altering a building's exterior as an example, and says to contact its Building Standards Department before you begin work, at 905-475-4870. That page does not mention repainting by name, so do not assume either way.
We could not find a plain statement for the Vaughan side. Vaughan's Thornhill district plan says its review focuses mainly on work visible from the public street. If your house is in either district, ask the City in writing whether your specific repaint or colour change needs approval, and keep the answer. Outside a heritage district, repainting an existing exterior is maintenance, but if you are unsure which side of the line your street is on, see our guide to how your side of Yonge Street changes the rules.
What to ask for in the quote
- Washing and mildew treatment, written as a line item.
- How many square feet of wall and trim are included, and how many storeys.
- Which primer goes on bare wood, and which exterior paint goes on top.
- How old paint is handled on a pre-1990 house.
- Whether HST is in the number.
Quick answers
How much does it cost to paint the outside of a house in Thornhill?
General estimates run about $3.50 to $6 per square foot of wall before HST, so roughly $6,300 to $10,800 for 1,800 square feet. Prep, height and old paint push it up.
Do I need a permit to repaint my house in Thornhill?
Usually not for the paint itself, but a home in a heritage district is the exception. Markham says exterior changes there need a heritage review, so call before you start.
Does the paint on my Thornhill house contain lead?
Health Canada says a home built before 1960 probably does, and the exterior of a 1960 to 1990 home may. Test it before you sand or scrape anything.
Why does paint fail faster under big trees?
Shade keeps siding damp, and damp wood grows mildew and lets paint blister and peel sooner. A wall that dries slowly needs more prep and a better primer.
Who can I call to paint my Thornhill house?
Rhodex can send a vetted craftsman; request a quote at rhodex.ca/get-a-quote.html. Ask the quote to say how it handles prep, old paint and any heritage check.
Related reading
- Exterior painting from Rhodex: get a fixed price
- More home repair guides for Thornhill
- Touch-Up Painting and Caulking in a Thornhill Heritage District: What Needs a Permit?
- Window and Door Resealing Before Winter in Thornhill: Repair, Heritage Permit or Replace?
- Deck and fence repair on an older Thornhill lot
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