What it usually means, the likely causes in order, what to safely try first, what a pro charges in Canada, and when to stop and call one.
This guide covers the common cases. Describe your exact problem and get a personalized diagnosis — free to start, with a DIY vs. call-a-pro verdict and a real cost estimate.
A crack along a drywall seam or corner is, most of the time, the house moving a little and the finish admitting it. Framing lumber dries and shrinks, seasons change humidity, and homes settle gradually, and the rigid joint between two boards is where that tiny movement shows first. Those cracks are cosmetic and need re-taping and mudding, not worry. The cracks worth a second look are the ones that keep growing, open wide, run diagonally, or arrive with sticking doors and sloping floors. Learning to tell a settling crack from a movement crack is the whole skill here, and it mostly takes watching, measuring, and time.
Most seam and corner cracks are not urgent and can wait for a convenient repair visit. Check in more promptly if a crack is visibly growing over a few weeks, is wide enough to fit a coin edge into, shows one side sitting higher than the other, or appears alongside new cracks elsewhere, sticking doors, or uneven floors. Those combinations suggest ongoing movement, and the cause deserves an opinion before the crack is simply filled again.
Newer framing dries out over its first seasons and shrinks slightly, and every house settles a little into its footings. The movement is tiny but concentrates at board joints and corners, producing thin, straight cracks along seams that stay the same size once the house has finished its early settling.
If the paper or mesh tape over a seam was set with too little compound, dried too fast, or was applied over a dusty surface, it eventually lets go, and the crack follows the seam in a neat straight line, sometimes with the tape itself lifting or bubbling at the edges.
Wood framing and drywall expand and contract slightly as indoor humidity swings between a dry heated winter and a humid summer. Cracks from this cause often open a fraction in one season and nearly close in another, and they tend to reappear in the same familiar places year after year.
Less common, but the one to rule out. Soil shifting under a footing, a failing support, or a load change in the house can keep a crack growing, widen it, or throw it diagonally across a wall or from the corner of a door or window opening. These cracks usually bring company: other cracks, sticking doors, or floors that feel out of level.
| Job size | Typical estimate (CAD) |
|---|---|
| Simple fix — the straightforward version of this repair | $100–$220 |
| Major job — complex, hidden, or replacement-level work | $400–$2,000 |
Estimates only, calibrated to Greater Toronto Area trade rates and adjusted by region on this site — not a quote. Your exact price depends on the cause, parts, and access. A personalized diagnosis narrows this range using your specific symptom.
Stable hairline seam cracks are reasonable DIY if you do the unglamorous part properly: cut out loose tape, re-tape with compound bedded fully under it, feather several thin coats wider than feels necessary, sand, prime, and paint. Hire a pro when the crack is on a ceiling, runs through a corner you need crisp, or keeps returning after a careful repair. A crack that grows, widens, or arrives with other movement symptoms should be assessed for its cause first, because the finest mudding in the world cannot hold a wall that is still moving.
Usually not. The large majority of seam and corner cracks are settling, shrinkage, or tape failure, all cosmetic. Foundation or structural concern rises when cracks are wide, growing steadily, offset from side to side, run diagonally or in stair-steps, or come with sticking doors, sloping floors, and matching cracks in several places. That combination, rather than any single crack, is what merits a professional structural assessment.
Filler in a crack that is still moving, or over tape that had already let go, is a temporary disguise rather than a repair. The joint needs the loose tape removed and new tape properly bedded in compound so the two boards are bridged, then thin feathered coats. If a correctly re-taped joint still reopens, the movement itself is ongoing, and the cause, not the mud, needs attention.
Hairline cracks you can barely fit a fingernail into are routine cosmetic fare. A crack you can fit the edge of a coin into, one where the two sides sit at different heights, or one that keeps widening between monthly photos has outgrown the purely cosmetic category. Width alone matters less than behaviour: a stable wider crack from an old event is less concerning than a thin one that is actively growing.
For a new crack with no other symptoms, watching briefly is genuinely useful: photograph it dated, mark its ends lightly in pencil, and recheck in a few weeks. If it has not moved, repair it with confidence. If it has grown, you have saved yourself a failed repair and gained the evidence a professional needs. Long-standing cracks that have clearly been stable for seasons can simply be repaired.
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