What Should You Do About a Bulging Ceiling?

Why the ceiling bulges

A plasterboard ceiling is a thin sheet of gypsum between two layers of paper, screwed to the joists. Water that gets in above it soaks into the board and the insulation on top. As more arrives, the water pools in the lowest point between the joists, and the board softens and sags under the weight. A bulge the size of a dinner plate can hold several litres. Plaster ceilings on lath, found in older houses, behave in the same way, but are heavier, and can come down in one piece.

The source is usually a leak in the roof above. It might be a slipped tile, a failed flashing, a split in a flat roof covering, or a blocked gutter. In some houses it is a burst pipe or a leaking tank in the loft, which is a plumber's call, not a roofer's. Look in the loft if you can reach it safely, because the shape of the stain on the insulation tells you where the water entered. Our guide to water coming through the ceiling goes through the steps in order.

The first five minutes

Move people and valuables away from the area. If the bulge is near a ceiling light, a smoke alarm or a fan, treat it as an electrical hazard: turn off the power to that circuit at the consumer unit, without standing in water, and do not touch fittings that may be wet. Our page on a roof leak near lights or electrics covers this in more detail.

Place a bucket or large tub under the bulge, and cover the floor and furniture with sheeting.

Releasing the water in a controlled way

If the ceiling is going to fail anyway, it is better to let the water out in a controlled way than to have the whole section drop. Stand to one side, not under it, and wear eye protection if you have it. Pierce the lowest point of the bulge with a screwdriver or a similar tool on a long handle. Water will run out, usually in a rush at first and then slowing. Let it drain into the bucket, and repeat in other low points if there are any. If the ceiling is cracked, flaking or hanging low, or you are unsure, leave it alone, keep clear and call for help.

Do not push on the bulge, do not stand beneath it and do not try to hold it up. A full ceiling can weigh more than you think, and the board can come away from the joists with little warning.

Stopping more water getting in

Once the immediate danger is dealt with, the next step is to stop the leak. In heavy rain, that may mean a temporary cover on the roof. We can arrange a tarpaulin or a temporary patch to hold the roof until a proper repair can be done, and emergency calls come ahead of routine work. Our guide to temporary roof repairs and tarpaulins explains what works. Please do not go up on a wet roof yourself.

After the water has drained

A ceiling that has held water is almost always replaced. The board has softened, the paper face is stained and the insulation above is wet. Wet insulation loses its value and holds damp against the timbers. We can open up the area, check the joists for rot and let the structure dry before the ceiling is boarded again, although plastering and decorating are done by another trade. If you plan to claim, photograph the bulge, the stain and the water in the bucket before you clear anything, and see our guide to claiming off house insurance for a leaking roof.

When the water is not from the roof

Not every bulge comes from rain. A ceiling under a bathroom can fill from a leaking bath seal or waste, and one under a loft tank can fill from an overflow or a weeping joint. If the bulge appeared on a dry day, or the stain is brown and spreading under a bathroom, shut off the water at the stopcock and call a plumber. A roofer can tell you quickly whether the roof is the source, and we will say so if it is not.

Fixing the cause

The repair on the roof depends on what we find. A slipped tile or a lifted flashing is a quick job, while a worn flat roof covering is a bigger one. We survey the roof, photograph the fault, and price the repair in writing, fixed. The roof side of the work comes under our emergency and general roof repairs service.