Drywall and Plaster Repair in Markham: Unionville vs. New

Published 2026 — Rhodex

Older Unionville homes usually have plaster and old paint, so check for lead before you sand and expect a slower repair. Newer Markham builds have drywall, and in the first year cracks and nail pops may be a Tarion warranty matter, not a repair bill.

A hairline crack looks the same on a Main Street Unionville character home and on a ten-year-old Cornell townhouse, but the right response is almost opposite. One wall is hard, wet-applied plaster over wood strips, possibly under decades of paint. The other is half-inch gypsum board that is still drying out and settling. Here is how to tell which you have and what that changes.

Step one: know what the wall is made of

Take the cover plate off an outlet or switch and look at the cut edge of the wall. A thick, hard coat over gapped wood strips (lath) means traditional plaster. A uniform board with paper on both faces means drywall. Plaster walls also sound solid and cold when you knock, and a thumbtack barely goes in. Some older houses are both, because drywall was sometimes screwed over tired plaster during an earlier renovation.

The older Unionville home: plaster, paint and a pause before the sander

In plaster, a fine crack can be opened slightly, filled and painted. A crack that keeps returning, or a wall or ceiling that bulges, usually means the plaster has lost its grip on the lath. Smearing filler over that hides it for a season. Loose sections are normally re-secured or cut out, which is plasterer's work, particularly overhead.

Before anyone sands, ask what is in the paint. Health Canada says a home built before 1960 probably contains lead-based paint. For homes built between 1960 and 1990 the exterior may contain it, and interior paint can hold smaller amounts that may still harm young children. Its advice is plain: do not use sanders, heat guns or blowlamps on lead-based paint, because that creates toxic dust and fumes. You can mail paint chips to a lab, or hire someone with the right equipment to test the surface. Intact paint left alone is often safer than paint that has been disturbed.

Asbestos is the second question. Ontario's asbestos regulation, O. Reg. 278/05, applies to construction projects and to the constructors, employers and workers on them, and asbestos-containing drywall joint compound is treated by the consultants who deal with it as a regulated removal job. We could not confirm from the regulation text what it means for a homeowner doing their own work, so do not scrape or sand old joint compound or textured ceilings yourself to find out. If your walls are old, ask any contractor whether they sample before they sand.

Heritage rules in Unionville: mostly about the outside

Unionville's Main Street is a Heritage Conservation District. The City of Markham's heritage permit page says a permit is needed before external building or property alterations on individually designated properties and on any property in a district. The page does not mention interior work, so patching plaster inside is not what that permit is about. We did not find a Unionville-specific written statement on interior work, so if your house is individually designated, a quick call to heritage staff before you start is cheap insurance. Our guides on exterior repairs in the Unionville district and window and door repair on a heritage home cover the outside.

The newer Markham build: check the warranty before you hire anyone

If your home is a newer build in Cornell, Markham Centre or elsewhere and is enrolled in Ontario's new-home warranty, the first year changes the picture. Tarion's published guidelines say cracks from normal shrinkage as materials dry after construction are excluded from the statutory warranty (FH 9.4), and so are nail or screw pops caused by that same shrinkage (FH 9.6). Repairs of those are at the builder's discretion, and the guideline notes they are often best left until the framing has settled.

Ceiling cracks along the wall, often called truss uplift, get their own guideline, FH 9.5. Crack width over 4 mm is not acceptable, and Tarion says repairs should be deferred until the truss returns to its original position. That is why a crack that opens in January and closes by summer is a poor moment to hire a painter. Photograph the widest point with a ruler beside it now and again in spring.

Tarion's Year-End Form is the last chance to report one-year items. You can start adding items on day 183 after possession, and it is submitted automatically on day 365, with a 10-day grace period that requires written proof you reported the items to your builder. Anything you patch yourself before reporting it can muddy the claim, so report first and repair second.

What a small repair typically costs

These are general estimates from published Ontario contractor guides, not quotes, and not what any particular tradesperson will charge you. Small drywall patches, such as nail pops and holes up to roughly fist size, are commonly listed at about $120 to $250 before HST, and many contractors set a minimum call-out of roughly $150 to $250, so grouping several spots into one visit is usually better value. Ceilings run higher because of access. We could not find a reliable Ontario price for plaster repair, and online figures vary widely, so get a written quote for your specific damage and ask whether HST is included.

Which job is which

Hairline crack, drywall, house under a year old: note it, photograph it, report it to the builder, wait for the seasons.
Hairline crack, plaster: repairable, but test the paint first if the house predates 1990.
Bulging plaster or a stain below a bathroom or roof: find the leak first; soft plaster usually comes down.
Several nail pops in an older drywall house: a one-visit job, ideally bundled.

Quick answers

How do I know if my Markham wall is plaster or drywall?

Look at the cut edge behind a removed outlet or switch plate. Wood strips under a thick coat mean lath and plaster; a uniform paper-faced board is drywall.

Is a ceiling crack in my new Markham home covered by Tarion?

Possibly, in the first year. Tarion's guideline calls ceiling-to-wall cracks wider than 4 mm unacceptable, but cracks from normal drying shrinkage are excluded from the warranty.

Do I need a heritage permit to patch plaster inside a Unionville house?

Markham's heritage permit page covers external alterations and does not mention interior work. If your house is individually designated, confirm with the city's heritage staff first.

Is it safe to sand old paint on a Unionville wall before patching?

Not until you know what is in it. Health Canada says a home built before 1960 probably contains lead-based paint and warns against using sanders on it.

How much does a small drywall patch cost in Ontario?

Published contractor guides put a small patch at roughly $120 to $250 before HST, often with a $150 to $250 minimum call-out. Treat that as a general estimate, not a quote.

Fix it once

The cheapest repair is the one that matches the wall. Identify the material, know your warranty position, and test the paint before sanding, and a small crack stays a small job. If you want a vetted craftsman to quote a patch, you can request a fixed price.

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Drywall and Plaster Repair in Markham: An Older Unionville Home vs. a Newer Build