Damp Ceiling After a Roof Leak: What Next?

A damp ceiling cannot dry while water is still arriving from above. If the roof has not yet been repaired or covered, that comes first, and our page on what a roof make-safe is explains how a roofer stops further damage in the meantime. Until then, move furniture and bedding out of the way, stand a bucket beneath every drip and spread towels or a plastic sheet around it.

If a ceiling is bulging with trapped water, do not poke at it from underneath in a way that sends the lot down on you. Stand clear, place a bucket beneath, and pierce the sagging centre with a screwdriver so the water drains in a steady trickle. A bulge like that can fail without warning, so keep children and pets out of the room.

Check light fittings. Water and electrics are a poor mix, so if water is running into a fitting or the ceiling rose, turn the lighting circuit off at the fuse board and stay out of the room until an electrician has looked.

Once the water has stopped, the job is to dry everything that got wet, and that includes more than the visible stain. Insulation above the ceiling soaks up water like a sponge and keeps the plasterboard damp from the top, so wet insulation should be lifted out and replaced if it will not dry. Timber in the roof space needs a look too, in case it has been wet for long enough to start to rot.

Inside the room, open windows when the weather allows and keep the air moving. A fan helps, and a dehumidifier will draw moisture out of the air over a few days. Turn the heating up gently rather than blasting it, since fast heat can crack plaster. Give the ceiling time. It can look dry and still be damp beneath the paint.

A damp meter, which a roofer or builder will have, tells you more than your eyes do. If the reading stays high after the weather has been dry for some time, something is still wet, and a second leak or condensation may be at work, as our page on condensation or a roof leak explains.

Mould can start to grow on a damp ceiling within a few days of it getting wet, appearing as black or green speckles near the stain or along the edges. Small patches on a painted surface can be wiped with a mould cleaner, using gloves and good ventilation. If the patch keeps coming back, covers a wide area or sits on soft plaster, the surface is still damp and needs to be dealt with properly. If anyone at home has breathing problems, ask a professional to look at it.

Plasterboard usually has to come out if it sags, feels soft or crumbles when pressed, if the paper face has peeled, or if the stain returns after the ceiling has dried. Boards that have been soaked once and stayed firm may dry out and take new paint after sealing with a stain-blocking primer. Older lath and plaster ceilings are different, since wet plaster can drop its key and come away in sections, so treat any bulge with care.

A builder or plasterer can cut out the damaged area, re-board it and skim the joint. The roofer's job is to make sure the roof above is sound before the new board goes up.

The order matters, and doing it the wrong way round costs money. First comes the roof repair, or a make-safe if the lasting job must wait. Second is drying the loft and the room. Third is the ceiling itself, whether that is a patch, a new board or a skim. Painting comes last, after a stain-blocking coat, and not before a damp meter says the ceiling is dry.

It helps to have the roofer tell you in writing what caused the leak and what has been done, with photographs of the fault. A plasterer will want to know the roof is mended before starting, and an insurer may ask for the same evidence. Keep dated photographs of the damage, the repair and the drying, along with receipts. If you tell your insurer, do so before work that changes the damage.

If the stain is on a ceiling below a flat roof, a dormer or a valley, the cause may need tracing before anything is done. Our page on water coming through a ceiling goes through the first steps, and the emergency and general roof repairs hub covers the repair itself.