The short answer
Ceiling cracks are usually caused by movement in the floor structure above, failed joints between plasterboard sheets, or the ceiling finish itself breaking down. The pattern of the crack is the clue: dead-straight lines follow board joints, random crazing is a finish problem, and cracks at the wall junction are deflection.
Read the pattern
Straight cracks at regular spacing are following plasterboard joints. The scrim tape or jointing compound under the skim has failed, usually because the boards moved relative to each other.
A crack running around the perimeter where the ceiling meets the wall is deflection — the joists flex under load and the ceiling drops away from a wall that stays put.
Fine random crazing across a whole area is the finish, not the structure: over-trowelled skim, a suction problem in the background, or old distemper or artex coatings breaking down.
A crack in one localised patch, sometimes with a slight sag, points at a fixing failure or something above — often a leak that dried out months ago.
What drives the movement
- Joist deflection from normal live loads — people, furniture, a bath filling upstairs.
- Timber shrinkage as joists dry out, especially in newer properties.
- Loft loading. Boarding a loft and stacking it with storage puts weight on ceiling joists that were never sized for it.
- Historic water ingress that weakened the plaster or the board's paper face.
- Poor board fixing — screws missed the joist, or boards were butted without support behind the joint.
- Vibration from a boiler, extractor or a busy road, working on an already weak joint.
Why the quick fix fails
Filling a ceiling crack and painting over it is the single most common repair and the one that reappears fastest. A ceiling crack is nearly always a joint or a movement issue, and filler cannot resist either.
There is also a safety element worth respecting. If a ceiling is sagging, sounds hollow when tapped, or is a lath-and-plaster ceiling in an older Leamington property, it can be closer to coming down than it looks. Poking at it to see how bad it is occasionally answers the question rather dramatically.
Working out whether you are dealing with a joint, deflection, a finish failure or a fixing failure decides everything about the repair — including whether the ceiling can be patched at all or is better overboarded.
How we put it right
Plastering repairs — patches from £75, full wall skim from £180
We identify whether it is a joint, deflection or finish failure, then repair to suit.
Serving Leamington Spa, Warwick, Kenilworth, Whitnash, Cubbington, Southam and surrounding Warwickshire.
Common questions
Is a cracked ceiling dangerous?
Most hairline cracking is cosmetic. A ceiling that is sagging, bulging, sounds hollow over a wide area, or is dropping debris should be treated as urgent and not loaded from above until it has been looked at.
Why does the same ceiling crack keep coming back after filling?
Because the joint underneath is still moving. Until the joint is reinforced or the source of movement addressed, any rigid filler will crack along the identical line.
Can a cracked ceiling be patched or does it need re-skimming?
It depends on how widespread the cracking is and whether the existing plaster is still bonded. Isolated joint cracks patch well; widespread crazing or a debonded finish is usually better overboarded or re-skimmed.