Cracks in the ceiling are one of the most common concerns Australian homeowners ask about. Some are harmless. Some signal something serious. This guide explains how to tell the difference, what causes the different crack types, and how each one's properly repaired.
Why ceilings crack
Every ceiling moves. Temperature swings, humidity changes, building settlement, vibration from traffic or wind — buildings breathe and shift constantly. Ceiling cracks are usually evidence of that movement reaching a point the surface couldn't accommodate.
The question isn't "is movement bad?" — movement is normal. The question is whether the crack pattern tells us something more is going on.
Hairline cracks (usually cosmetic)
The most common type. Fine, sometimes barely visible, often appearing at the cornice line where the ceiling meets the wall. Cause: seasonal expansion and contraction of the building. These cracks are almost always cosmetic — they appear, widen slightly with summer heat, close back with winter cooling.
Repair approach: re-tape and re-set the crack, sand, repaint. For ceilings with multiple hairline cracks across the surface, consider whether the underlying ceiling is reaching the point where replacement is more cost-effective than repeated repair.
Cracks along sheet edges (joint failure)
Cracks running in straight lines along the plasterboard joints typically mean the original taping has failed. Causes: building movement greater than the tape could accommodate, or original tape applied with insufficient setting compound.
Repair: cut out the failed tape, re-tape with paper or mesh tape, three-coat set, sand. Usually a clean fix that lasts.
Cracks around fittings (point stress)
Cracks radiating from a downlight, fan fitting, or ceiling rose mean the fixture is stressing the surrounding plasterboard. Causes: fixture too heavy for the cavity above, fixture mounting working loose, or original cutout damaging the surrounding board.
Repair: address the fitting first (proper bracing, re-mounting, weight-rated fixture), then repair the cracking around it.
Wide cracks running diagonally (structural)
Wide cracks, especially those running diagonally rather than parallel to walls, signal structural movement — settling foundations, framing failure, or significant load redistribution above. These are not cosmetic problems.
Don't just repair the visible crack. Get the cause assessed first — often by a structural engineer if the cracking is severe. Repair without addressing the cause means the crack returns, often wider, within a year.
Cracks combined with sagging
If a crack appears at the same time as visible sagging or dipping in the ceiling surface, the ceiling has lost structural integrity. Patch repair is not the right answer. The honest approach is removal and replacement of the affected section back to sound framing.
Cracks in ceiling plaster (older homes)
Cracks in older plasterglass ceilings (pre-1980s Australian homes) behave differently from cracks in modern Gyprock. Plasterglass is more brittle, ages more aggressively, and patches in plasterglass rarely bond cleanly to the surrounding board.
Our honest advice for cracking in plasterglass ceilings: don't keep patching. Plasterglass that's cracking in multiple places is at end of life. Replacement with modern plasterboard is the lasting fix.
Repairing cracks in the ceiling — DIY vs professional
What you can DIY
- Single hairline cracks under 1m long.
- Cracks in flat, sound, easily accessible ceilings.
- Cosmetic-only cracks where you're comfortable with painting afterward.
For DIY, scrape out loose material along the crack, apply flexible filler designed for ceilings (rigid filler will crack again), let dry fully, sand smooth, paint to match.
When to call a professional
- Cracks wider than a credit card edge.
- Cracks that have returned after previous repair.
- Multiple cracks across the same ceiling.
- Cracks combined with sagging, soft spots, or water staining.
- Cracks in plasterglass (older fibrous plaster) ceilings.
- Cracks around significant fittings or beams.
- Any crack you're not sure about.
Repair process for non-DIY cracks
- Inspect to determine cause — cosmetic, joint failure, structural.
- Address any underlying cause before surface work.
- Cut back to sound material along the crack.
- Re-tape with paper or mesh tape, depending on the situation.
- Three-coat set, feathered well past the repair zone.
- Full sand to a paint-ready finish.
- Hand over for painting.
Ceiling crack repair cost
Small single-crack repair as part of broader work is generally inexpensive. Standalone callouts for crack-only work cost more proportionally because the setup time is the same regardless of how much surface is being repaired. Whole-room re-set work (multiple cracks repaired across a single room) gets back to economic per-metre rates.
When to stop repairing and replace
If you've repaired cracks in the same ceiling more than once or twice, the ceiling is telling you something. Continued repair of an ageing ceiling is throwing good money at a problem that will return. At some point, the honest answer is replacement.
Frequently asked
Hairline cracks are almost always cosmetic. Wide cracks, diagonal cracks, or cracks combined with sagging can indicate structural issues that need professional assessment.
Because the underlying cause wasn't addressed. Surface repair without diagnosing the cause is masking the symptom.
Flexible filler for ceiling cracks — rigid fillers will crack again with the next seasonal movement.
Rarely. Most ceiling cracks are seasonal or material-related. Sinking foundations show in walls and door frames more obviously than in ceilings.
Briefly. Paint over an active crack and the crack reappears through the paint within weeks. Surface repair first, then paint.
Need this work done in Perth?
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