Window and Door Resealing in Markham Before Winter

Published 2026 — Rhodex

Reseal Markham windows and doors in the last dry days of October: caulk fixed joints, weatherstrip the parts that open. What you may do depends on the home. A heritage-district house, a pre-1960 frame and a new build each have different rules.

Markham is not one kind of housing. Within a few kilometres you have Victorian houses on Unionville's Main Street, post-war homes around Markham Village, and Cornell and Markham Centre homes built in the last two decades. The draft behind a window looks the same in all of them, but the right fix and the paperwork around it are not. This guide covers the three questions that decide the job: what is the leak, what is the home, and who has a say.

Find the leaks before you buy anything

Manitoba Hydro's sealing guide starts with the same step every utility does: work out where air is getting in. On a windy day, hold a strip of plastic or a thin piece of paper near the frame. If it flutters, that spot leaks. Check the joint between the frame and the wall, the gap where the sash meets the frame, and the bottom of every exterior door. Mark each spot with painter's tape so you fix what you found rather than what you guessed.

Caulk and weatherstripping do different jobs

Caulk seals joints that never move, such as where a frame meets brick, siding or trim. Weatherstripping seals parts that open and close: sashes, door slabs and the track of a patio slider. Caulking a moving gap cracks within a season, and weatherstripping in a fixed joint does nothing. Replace a worn door sweep from the inside at the same time. Read the tube for its minimum application temperature and its cure time, and plan the exterior work for a dry spell. Interior joints can wait for a cold day because the house is heated.

If you are in a heritage district: Unionville and Markham Village

The City of Markham has four heritage conservation districts: Thornhill, Markham Village, Buttonville and Unionville. Its heritage page says owners in any of them must obtain approval for exterior alterations, through a minor or major heritage permit, and that staff can approve work that follows the district's approved policies. A fresh bead of caulk or new weatherstripping keeps a window as it is. Replacing a window, or changing its material, profile or the way it looks from the street, is the kind of change that needs the permit conversation.

The practical rule: reseal and repair freely, but ask Markham's heritage staff before you replace anything visible. Our guide to window and door repair on a Unionville heritage home goes through what can and cannot be swapped. If you are unsure whether your street is inside a district, ask the city before you book a contractor, not after the old windows are on the lawn.

If the house is older: check the paint first

Health Canada says a home built before 1960 probably has lead-based paint, and that the exterior of homes built between 1960 and 1990 may. Much of the housing around Markham Village and old Unionville falls in the first group. Health Canada's advice is not to sand, scrape or burn off leaded paint, because it releases harmful dust, and to consider an expert if you suspect lead. Cutting out a worn bead of caulk is a small disturbance. Stripping an original frame back to bare wood is not. If a quote includes scraping or sanding, ask how the paint will be tested and contained.

If the house is new: the warranty may matter more than the caulk

Many Cornell and Markham Centre homes are newer builds. Tarion, Ontario's new-home warranty provider, says the builder's two-year warranty covers water penetration into the building envelope, which includes openings for windows and doors. Its standards say defects that let water in around those openings must be repaired. They also say damage from improper maintenance, normal wear and tear, and alterations by the owner are not covered. So if a new window leaks in the rain, do not caulk over it first. Document it with dated photos, report it to the builder in writing within the warranty period, and let the builder fix the cause. Resealing it yourself can make the claim harder.

Past the warranty years, a newer build has the same upkeep as any other home: shrunken caulk at the siding or brick joints, compressed weatherstripping on the patio door and a worn garage-to-house door seal.

When resealing is not the fix

Fog or moisture trapped between the panes means the sealed glass unit has failed, and no caulk repairs it. Soft, spongy wood at the bottom of a sash or at the sill is rot, which needs repair before any seal. A door or slider that no longer closes square may need adjustment or new hardware rather than more weatherstripping. If a frame is rotten or the glass unit has failed, get the scope in writing before deciding between repairing and replacing.

A short sequence that works

Find the leaks on a windy day and mark them.
Decide the category: heritage district, pre-1960 or 1960-1990 paint, or a home still under Tarion warranty.
Reseal exterior joints in a dry stretch in late October or early November.
Replace worn weatherstripping and door sweeps from inside.
Keep bathroom fans and the kitchen hood working. A tighter house needs ventilation more, not less.

Quick answers

When should I reseal windows and doors in Markham?

Do the exterior caulking in the last dry, mild days of October or early November. Check the tube label for its minimum application temperature, because caulk applied too cold or damp fails.

Do I need a heritage permit to reseal a window in Unionville?

Not for routine upkeep as such, but Markham requires approval for exterior alterations in its four heritage districts. Ask heritage staff before changing how a window looks.

How do I find a draft around a window?

Hold a strip of plastic or a thin piece of paper near the frame on a windy day. If it flutters, air is getting through at that spot.

Is a leaking window in a new Markham home covered by warranty?

Possibly. Tarion's two-year warranty covers water getting into the building envelope through windows and doors, but not damage from improper maintenance. Report it in writing within the warranty period.

Should I scrape old paint off a Markham window frame before caulking?

Not on an older home without testing first. Health Canada says homes built before 1960 probably have lead paint and warns against sanding or scraping it.

Do the exterior first, while the weather allows

The outside joints are the only part of this job with a deadline. If you would rather hand it over, describe your windows and doors on Rhodex and ask for the scope in writing: which joints get caulk, which parts get weatherstripping and what happens to old paint. Get a fixed price.

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Window and Door Resealing Before Winter in Markham: Heritage District, Older Home or Newer Build?