Every year, a few weeks after the furnace comes on, the same calls start. A hairline crack has appeared over the bedroom door. There are small round bumps in the ceiling that weren't there in August. A seam in the hallway has opened up.
Most of the time, nothing is wrong with the house. It's just drying out. Here's what's happening, which cracks to take seriously, and how to fix the rest so they don't come straight back.
Why it happens when the heat comes on
Toronto summers are humid. The wood framing in your walls and ceiling soaks up some of that moisture. When the furnace runs all day in November, the air gets very dry, and the wood slowly gives that moisture back and shrinks a little.
Drywall doesn't shrink with it. It's screwed or nailed to the wood, so when the framing moves, the drywall takes the stress. It shows up in predictable places:
- The corners of doors and windows. Those are the weak points in a wall, so cracks run diagonally up from the corners.
- Taped seams. Where two sheets meet, the tape can crack or lift.
- Nail pops. A small round bump or a cracked circle of paint over a nail head. The stud has shrunk away from the drywall, and the nail head is left proud of the surface.
- Where the ceiling meets an inside wall. In some houses with roof trusses, the trusses lift slightly in winter and pull the ceiling up off interior walls, leaving a crack along the corner that closes again in summer.
New builds get this the most in the first couple of winters, while the lumber settles. You'll see it in a lot of newer homes in Brampton, Vaughan and Markham. Older Toronto houses move too, just more slowly.
Condos are a bit different
Condo towers in places like North York and Downtown Toronto are concrete, and interior walls are usually drywall on steel studs. They don't shrink like wood. The cracks you see are usually at seams, around bulkheads, or where drywall meets the concrete. They're mostly cosmetic, but a crack with a water stain next to it is a different story. More on that below.
Which cracks to take seriously
Most winter cracks are hairline, straight or diagonal, and stop growing after a few weeks. Call someone to look closer if you see:
- A crack wider than a coin's edge, or one that keeps getting longer
- Doors that suddenly stick or swing open on their own at the same time
- Stair-step cracks in brick or block, or new cracks in the foundation
- A crack with brown staining, bubbling paint or soft drywall around it
Staining or soft drywall means water, and water needs to be traced before anything gets patched. In a condo, tell management, because the source may be a neighbour's unit.
How to fix them properly
Nail pops. Pushing the nail back in doesn't last. The fix is to drive a drywall screw just above and below the pop to pull the sheet tight to the stud, then set or remove the old nail, fill, sand, prime and paint.
Seam and corner cracks. Filling a crack with compound alone usually brings it right back. The crack needs to be opened up slightly, covered with tape (mesh or paper), coated a couple of times, sanded and primed.
Truss uplift cracks. These open and close with the seasons, so a rigid repair just cracks again. Often the better answer is a flexible caulk in the corner, or a small trim moulding attached to the ceiling only, so it rides up and down without showing a gap.
Then paint. A patch shows if the sheen doesn't match. Sometimes the best result is repainting the whole wall, corner to corner. We explain why in planning a drywall patch and paint.
Timing: now, or in spring?
If the cracks are small and cosmetic, many people wait until late winter, when the house has done most of its moving for the year, and fix everything in one visit. If you're listing, hosting or handing over a rental, do it now and accept that a hairline might reappear.
Keep the air from getting too dry
A humidifier on the furnace or a portable one helps slow the shrinking. You want enough humidity that your skin and the hardwood floors aren't suffering, but not so much that windows drip with condensation on cold mornings. If the windows are sweating, turn it down.
Getting it fixed
Crack repair, nail pops, patching and painting are part of our drywall and painting service, and we're happy to fold them into a visit with other small jobs through general maintenance.
Got cracks or nail pops showing up? Call or text 416Fix at (365) 360-1416. Send a photo of each spot with something for scale, and tell us whether it's a house or a condo.
