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Repair suits homes of every era, from recent vinyl casements whose hardware has given out to century-old wood windows on a heritage street. In the Canadian climate, the payoff is felt mostly in winter: fewer drafts, less frost on the frames and sashes that lock tight against the wind.
This page covers the common window problems a technician can fix, how to decide between repair and replacement, how weatherstripping and caulking stop air leaks, what condensation says about indoor humidity, how to approach old wood windows and their lead paint, and when in the year to plan the work.
Common window problems a repair technician can fix
- A casement or awning crank that spins without moving the sash usually means a worn operator, which can often be replaced on its own.
- A sash that drags, binds or closes unevenly may have bent hinge arms, a frame that has shifted or layers of old paint in its tracks.
- A hung sash that slides down or won't stay open points to a broken balance, the spring or cord mechanism that holds it in place.
- A sliding window that grinds or jumps its track often needs new rollers and a cleaned-out sill track.
- Drafts along the sash usually come from weatherstripping that has flattened, torn or come loose.
- Cracked or missing caulking between the frame and the siding or trim lets in air and, in wind-driven rain, water.
- Soft, grey or crumbling wood on the sill or the bottom rail of the sash is rot, which can often be cut out and patched if caught early.
- Latches and locks that no longer pull the sash tight against its seal leave a draft even when the window is shut.
Window repair or replacement: how to decide
Natural Resources Canada's guide to upgrading windows ties the decision to the frame. If the frame is in poor condition, it may be time to replace the unit; if only the glazing has failed, a new sealed unit is the fix. Most of what lies in between, from cranks and balances to weatherstripping and small patches of rot, is repair work that leaves the frame, the trim and the seal to the wall undisturbed.
Counting the problems helps. One broken operator on an otherwise sound window is a short repair. When nearly every window needs new hardware, several sealed units have fogged and the sills are soft, the repairs start to demand as much effort as a replacement without delivering its gains. Ask the technician to write down the condition of each window, so you can repair the good ones now and plan to replace the worst.
Window weatherstripping and caulking: sealing air leaks
Window drafts follow two paths: between the sash and the frame, which is the weatherstripping's job, and around the frame, where caulking takes over. Inside, Natural Resources Canada recommends a continuous bead of caulk where the trim meets the wall, at the mitred corners of the trim and between the trim and the frame, using a good-quality indoor caulk that can be painted. Outside, the joint between the frame and the siding calls for an exterior sealant.
- Hung windows: NRCan suggests thin plastic V-strip along the sides, with compression-type neoprene where the bottom of the sash closes.
- Sliding windows: brush weatherstripping sits in slots, so the old strip is pulled out and a new one slid in.
- Casement and other hinged windows: usually a mix of V-strip and compression weatherstripping.
- Any window: match the new strip to the groove and thickness of the old one, since a strip that is too thick makes the sash hard to close and strains the hardware.
Window condensation: too much humidity or a failing window?
Condensation on the room side of the glass is mostly a humidity issue. Natural Resources Canada explains that it forms in cold weather when moist indoor air meets cooler surfaces, and that the risk rises as it gets colder outside and more humid inside. The lower edge of the glass and the frame tend to be the coldest parts of a window, so water and frost gather there first.
NRCan's advice is to keep air moving near the windows by not blocking them with drapes, furniture or deep sills, to run the heat recovery ventilator if the house has one, and to lower indoor humidity through ventilation. Its window guide also warns that new, tighter windows can make condensation worse, because the old leaky ones were letting humid air escape.
- Water or frost on the inside surface: indoor air is too humid for that window's surface temperature, so ventilation comes first.
- Fog between the panes: the edge seal of the sealed unit has failed, and only a new sealed unit will clear it.
- Dew on the outside of the glass on cool mornings: NRCan notes it can form around sunrise, even on high-performance windows.
- Stains or rot on the sill below: condensation has been running off for several winters, so repair the wood and deal with the humidity together.
Heritage wood windows: restoration or replacement
Old wood windows are often worth keeping. They were built to be taken apart and repaired piece by piece, and on an older facade they carry much of the building's character. The Standards and Guidelines for the Conservation of Historic Places in Canada favour minimal intervention: repair character-defining elements with recognized conservation methods, and replace in kind only the parts that are too far gone, where surviving examples exist to copy.
Restoration usually means freeing sashes that were painted shut, splicing new wood into rotten sections, re-glazing panes with fresh putty, adding weatherstripping and fitting a storm window. It keeps the original look while improving comfort. Replacement is the practical route when most of the wood is rotten or when the priority is a large gain in energy performance. On a heritage building or in a protected area, ask the municipality before choosing either route, since new sashes or windows may need approval.
What happens during a window repair, and lead-safe work on older windows
A technician starts by opening and closing each window, looking for markings that identify the model, and checking the hardware, weatherstripping, glass and wood. Common operators, hinges, balances and rollers can sometimes be swapped on the first visit; parts for older windows often have to be ordered or matched, which can mean a second trip.
On older wood windows, the paint needs attention before anyone scrapes it. According to Health Canada, lead-based paint is probably present in homes built before 1960 and may be on the exterior of those built between 1960 and 1990. Health Canada warns against removing it with sanders, heat guns or blowlamps, which release toxic dust and fumes, so ask how the crew will test the paint, contain dust and clean up, and keep children away from the work area.
The best season for window repair, caulking and weatherstripping
- Late spring to early fall: the best time for exterior caulking, since sealants need clean, dry surfaces and temperatures within the range printed on the tube.
- Early fall: renew weatherstripping and adjust latches before the heating season, while the windows can still stay open for a while.
- Winter: the season that reveals weak windows through drafts, frost lines and condensation, so mark them for repair once it warms up.
- Spring: after the snowmelt, check sills and the bottoms of sashes for water damage and repair soft wood before the summer rains.
- Any season: a window that won't close or lock, or broken glass, shouldn't wait, since it is both a security problem and a source of heat loss.
Window Repair: frequently asked questions
Can a broken window crank be replaced without replacing the window?
Usually. The handle and the operator behind it are separate parts, and many are still made in common sizes. Photos of the operator and any markings on the frame help the technician find a match; if the exact part no longer exists, a compatible one can often be adapted.
Why is there a draft even though my window is closed?
The weatherstripping may be flattened or torn, the latch may no longer pull the sash tight, or air may be coming around the frame where the caulking has failed. On a cold, windy day, run the back of your hand along the sash and the trim to find where it comes in.
Is it worth restoring old wood windows?
Often, when the wood is mostly sound. Restoration keeps the original look, which matters on heritage buildings, and adding weatherstripping and a storm window improves comfort. If rot runs through most of the frame, replacement may be the more practical choice.
How do I reduce condensation on my windows in winter?
Lower indoor humidity through ventilation: run your heat recovery ventilator if you have one, use the bathroom and kitchen fans and leave room for air to circulate around the windows. If the water appears between the panes instead, the sealed unit has failed and needs replacing.
Does a window repair contractor need a licence in Quebec?
A contractor who does window and door work for others needs a licence from the Régie du bâtiment du Québec, and subclass 8.0 covers doors and windows. Look up the licence on the RBQ website before the work starts.
Sources
- Keeping the Heat In, Section 8: Upgrading windows and exterior doors — Natural Resources Canada
- Condensation — Natural Resources Canada
- Lead-based paint — Health Canada
- Standards and Guidelines for the Conservation of Historic Places in Canada — Canada's Historic Places
- Specialized contractor licence subclasses — Régie du bâtiment du Québec
Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides
