Ceiling crack:
is it serious?

A ceiling almost always cracks for an ordinary reason: a joint tape that lets go, an old render that crazes, two materials that expand differently. Having a crack is therefore not the issue. The issue is knowing whether it is moving and whether it appears on its own.

The signs that should alert you. A crack whose length or opening grows between two checks. A ceiling that forms a hollow at its centre, or that curves along a beam. Plaster that swells, sounds hollow when tapped or leaves a fine white dust on the floor. Other cracks appearing in the partitions below or on the walls, doors that catch. A yellowish or damp ring.

In its booklet for individuals preparing a renovation, the Agence qualité construction lists deformation, cracks and fine cracking in ceilings among the defects that are easy to spot, and reminds readers that a structural problem never sorts itself out. A single crack, fine and stable, gets repaired. A crack accompanied by one of these signs is first explained.

On a plasterboard ceiling, the typical crack is straight, clean, and falls exactly on the junction of two sheets, often at regular intervals from one end of the room to the other. It is not the sheet that breaks, it is the joint: the tape and compound linking the sheets are the most fragile part of the ceiling, and that is where the slightest movement concentrates.

Why the joint splits. A tape laid without enough compound beneath it, which does not bond; a compound applied too thin or dried too fast, with the heating turned up on a site just finished; sheets not screwed enough, or a framework too flexible that lets the ceiling vibrate when someone walks upstairs; a large ceiling laid in one piece, without the control joints that the installation rules provide for, or one that passes from one substrate to another without a break.

Under a roof space, the ceiling follows the roof structure. A ceiling fixed under the tie beams or rafters moves with the timber: timber drying out in the first years, the weight of snow, wind on the roof. The cracks there often follow the direction of the roof members. They say nothing serious about the roof structure as long as they stay fine, but they will come back if you merely fill them.

In a new house or a freshly renovated flat, fine joint cracks in the first year are common: the building dries out and settles. This is precisely what the guarantee of perfect completion covers, detailed below: report them before the end of the year, even if they seem minor.

In pre-war houses and buildings, the ceiling is often a plaster render applied on lath: thin wooden laths nailed under the joists, between which the fresh plaster slid to form keys. This ceiling ages in two very different ways.

Crazing, almost always harmless. Very fine cracks, crossing like a cobweb, covering part or all of the ceiling: it is the surface render that has been working for decades. If the plaster remains flat, hard and stuck to its backing, a skim coat before painting is enough.

Detachment, to be taken seriously. With time, an old leak or vibrations, the plaster keys break and the render holds only by its own weight. The signs: an area that bulges or forms a belly, a crack that outlines a closed contour, a ceiling that sounds hollow and gives way when pushed gently with the flat of the hand, plaster dust on the floor in the morning, pieces falling. A section of plaster ceiling is heavy: until a professional has examined it, do not let anyone sleep or settle underneath, and do not fix anything to it.

Before taking down an old ceiling, the age of the building may require an asbestos and lead survey; our guide to redoing walls and ceilings details these obligations and the order of work.

Where plaster meets a timber beam, a joist or the top of a load-bearing wall, two different materials touch. They do not expand in the same way, and a fine, straight crack often ends up marking the junction. If it stays fine and does not change, it is a simple touch-up to redo.

It changes nature when the ceiling drops: a beam that deflects, a floor that sags in the middle of the room, that vibrates or creaks more than before upstairs. The Agence qualité construction points to an unmistakable clue: cracks in partitions placed under a floor show that a partition which carried nothing is now taking the loads of a floor that is deforming abnormally. A crack that appeared just after work upstairs, a partition knocked down, a load-bearing wall opened, a bath or a bookcase installed above, calls for the same check. Our article on opening a load-bearing wall explains why such work is calculated before it is carried out.

If the ceiling crack continues onto the walls, draws a staircase pattern in the masonry, comes with doors and windows that stick or worsens after a dry summer, the problem goes beyond the ceiling: it is the building that is moving. Our guide to cracks in a house explains how to read them, from foundations to façades.

A yellowish ring around the crack, paint that blisters, a plasterboard sheet that warps or sags between two rails: water has been through. Under a bathroom, under a roof, under a neighbouring flat or along a pipe, it seeps in, soaks the plaster and makes it heavier. A soaked plasterboard sheet loses its hold: it is replaced, not filled. Turn off the water if the leak is active, notify the occupant above or the syndic, then locate where the water gets in. Our articles on water infiltration in a wall and on damp walls help trace it to the source. Repainting before everything is dry makes the stain reappear within a few weeks.

Photograph it with a tape measure laid beside it, always from the same spot and in the same light.

Mark its ends with a perpendicular pencil line, with the date written beside it. If the crack goes beyond the line a few weeks later, it is lengthening.

Fit a crack monitor straddling the crack: a strip of paper glued on either side, or a small plaster pad. If it tears or splits, the crack is opening.

Watch over several seasons. A crack that opens in winter and closes in summer follows variations in temperature and humidity; a crack that opens a little more each season follows a movement that does not stop. At the same time, note doors that rub, windows that close badly, other cracks appearing: this log will save time for the person who comes to examine it.

Filling and repainting a ceiling that moves. The compound is rigid: at the first movement, it splits in the same place. A crack that returns after one winter is almost always a cause left in place.

Filling a large crack with sealant. An acrylic sealant suits a fine joint in a corner, not filling an open crack in the middle of a ceiling: it cannot be sanded like a compound and shows through the paint.

Hiding detached plaster under a lining or under plasterboard screwed into it. A glass-fibre lining masks the fine cracking of sound plaster, not the belly of a ceiling that is coming away. Screwing new sheets into old plaster that no longer holds means hanging extra weight on something that may fall.

Painting over a water stain. As long as water keeps arriving, the stain comes through every coat of paint.

1. A fine, stable crack. It is opened slightly with a scraper to remove what no longer holds, dusted, filled with compound, a reinforcing tape is embedded in a second pass, then skimmed wide so the repair disappears, before primer and paint. On one or two cracks, a careful DIYer can manage. On a whole ceiling, the quality of the skim shows as soon as light grazes the surface.

2. A plasterboard joint that keeps coming back. The repair starts above the compound: screws added where the sheet moves, framework redone if it is too flexible, control joint or flexible joint where it meets the walls when the ceiling needs to be able to move. The tape is then redone along the full length of the joint, not only where the crack shows.

3. Old plaster that is coming away. Three routes, depending on its condition and on what you want to keep. Consolidate it, when it carries mouldings or a cornice worth keeping. Fit a new plasterboard ceiling beneath, on a framework fixed into the joists and not into the old plaster: this is often the quickest solution, and it allows insulation or new spotlights to be slipped in, as our guide to the price of a false ceiling explains. Or take it down entirely when it threatens to fall or when the ceiling height does not allow a new ceiling beneath it.

4. A cause in the structure. A floor that deflects, a weakened beam, wall movement: the ceiling is repaired only once the structure has been examined and, if necessary, reinforced. This diagnosis falls to a structural engineering firm, which sizes the reinforcement. Redoing the ceiling beforehand amounts to paying twice for the same room.

These ranges are taken from our 2024-2026 quotes in Savoie and Haute-Savoie, supplied and fitted, excluding VAT. Ceiling repairs are carried out by our salaried craftsmen, each in their own trade: plasterboard fitters for new ceilings, tapes and framing, painters for preparation and finish, electricians when a new ceiling takes spotlights.

A crack on its own has no line of its own. Our quotes do not price the repair of a crack in isolation: it is part of preparing the ceiling before painting. On the ceiling paint lines of our quotes, three quarters already include filling, tapes or skimming, and our guide to the price of painting per m² shows what makes this item vary.

An example, a 12 m² bedroom. Cracks repaired and ceiling repainted: around €320 to €540 excl. VAT. New plasterboard ceiling fitted under the old one, ready to paint: €1,140 to €1,320 excl. VAT, paint extra. In a home completed more than two years ago, this work qualifies for the 10% VAT rate, i.e. about €350 to €590 incl. VAT for the first case and €1,250 to €1,450 incl. VAT for the second.

What we do not do. We do not carry out structural surveys or leak detection: when the crack depends on them, we tell you at the visit, and we price the ceiling repair once the cause has been dealt with.

In a rented home. Service-public.gouv.fr lists among the tenant's repairs small paint touch-ups and filling the holes they made, for example to hang a picture or a mirror. The law of 6 July 1989, however, exempts them from repairs caused by wear and tear, defective workmanship, a construction defect, an unforeseeable event or force majeure: a crack that comes from the building is the landlord's responsibility. Report it in writing, preferably by registered letter with acknowledgement of receipt, and date your photos.

In a co-owned building. A crack that goes through a concrete ceiling, that is also found at the neighbour's or that follows a leak from another flat concerns the building: notify the syndic as well as the occupant above.

After building work or in a new house. The guarantee of perfect completion runs for one year after acceptance: it covers the defects noted in the acceptance report and those that appear within the year, to be reported to the contractor by registered letter, with a deadline to act. The two-year functional guarantee (garantie de bon fonctionnement) applies only to equipment that can be removed without damaging the building: a ceiling is not part of it. The 10-year guarantee, finally, takes over for ten years for serious defects: those that threaten the soundness of the building or prevent its normal use.

And home insurance? A crack due to water damage covered by the contract, a leak or overflow from upstairs, may be covered under that cover, within the reporting deadline set by your contract. A crack that comes from movement of the building, after a dry summer or ground settlement, is first treated as a structural problem: our guide to cracks in a house explains what to do.