If your ceiling is bulging with water, keep everyone out from under it and switch off the electrics for that room at the consumer unit. Put a bucket beneath the lowest point, then pierce the bulge with a screwdriver to let the water out in a controlled stream. Turn off the stopcock, photograph everything, and only then start looking for where the water came from.
The ceiling has a belly in it. Plasterboard that was flat yesterday is sagging like a hammock, there might be a brown ring spreading round it, and it could be dripping from the middle or holding several litres and waiting. This is one of the few leak situations where the next ten minutes matter more than the next ten days. A ceiling full of water can drop without warning, and if a light fitting sits in the wet area the water and the wiring are in the same place. Below is the sequence to follow, then what to do once the drama is over. When the immediate problem is handled and the source needs finding, our trace and access service locates it and writes the report your insurer will ask for.
The first ten minutes
Minute one: people and power
Get children, pets and yourself out from under the bulge. Then go to the consumer unit and switch off the circuit for that room’s lights and, if you are not sure which it is, the main switch for the whole house. Do this with dry hands, standing on a dry floor. Do not touch the light switch in the wet room and do not touch the fitting. Water tracking through a ceiling finds the light fitting because it is the lowest hole, and a wet fitting can be live.
Minutes two and three: contain
Put a bucket, washing-up bowl or bin under the lowest point of the bulge. Move furniture, rugs and anything electrical out of the way. Lay towels or a dust sheet over what cannot be moved. If the bulge is over a bed or sofa, drag it clear; a collapsing ceiling brings wet plaster and insulation with it.
Minutes four and five: release the water
This feels wrong and is right. A ceiling holding water is far more likely to fail across a wide area than one with a small drain hole in it. Stand to the side, not directly underneath, and push a screwdriver or a skewer into the lowest point of the bulge. Water will run out in a stream into the bucket. If the bulge is long, make two or three holes along its lowest line. Let it drain fully. Do not push a hand up into the plasterboard and do not try to lift the ceiling back; it will tear.
Minutes six and seven: stop the supply
Turn off the internal stopcock, usually under the kitchen sink, and if you have a cold water tank in the loft, turn off the gate valve on its outlet if you can find it. If the leak is from heating pipework, switch the boiler off. If the ceiling is under a bathroom and the water only appears after someone showers, it may be waste pipework rather than the supply, and the stopcock will not stop it, but turning it off costs nothing while you work that out.
Minutes eight to ten: record
Take photographs of the bulge before and after draining, the water in the bucket, the stain, the room above and anything wet up there. Note the time. If you are going to claim, your insurer will want to see the damage as it was, not as it looks after you have cleaned up. The guide to claiming on home insurance for a water leak explains what else they will ask for.
Is the ceiling going to come down?
Do not be tempted to skip the drain holes because the bulge looks small. A blister the size of a dinner plate can hold several litres, and plasterboard loses most of its strength once it is wet through. The weight is concentrated on a few fixings, and those are what let go.
Once drained, a plasterboard ceiling usually stays up, though it will be soft, stained and may need replacing. A lath and plaster ceiling, which many older Cornish houses still have, is heavier and less forgiving, and a saturated section can come away in a slab. If the ceiling is lath and plaster, keep the room shut and keep people out until it has dried and been checked. Signs that any ceiling is still at risk:
- Cracks spreading out from the bulge, or a gap opening along the edge where the ceiling meets the wall.
- The bulge refilling after you drained it, which means the leak is still running.
- Sagging over a wide area rather than a single blister.
- A ceiling with insulation above it that is now wet. Wet mineral wool holds a surprising weight of water.
Working out where the water came from
With the water out and the supply off, look at what is directly above the bulge and what is near it, because water runs along joists and pipes before it drops.
| What is above | Most likely source | Quick check |
|---|---|---|
| Bathroom or shower room | Failed sealant round a bath or tray, a shower waste, or a supply pipe to the basin or toilet | Does it only appear after someone has bathed or showered? |
| Loft | Cold water tank overflowing, a burst pipe, or the roof | Look in the loft with a torch. Is the tank full to the brim or the underside of the felt wet? |
| A room with radiators | Radiator valve, tail or pipe under that floor | Is the boiler pressure low? Is the water in the bucket dirty or slightly oily? |
| A flat roof or dormer | Rain getting in | Did it follow heavy rain rather than water use? |
| Another flat or a neighbour’s property | Their plumbing | Knock immediately; they may not know |
A ceiling that only gets wet after a shower, and dries out between, almost always points to the waste or sealant side rather than a pressurised pipe. A ceiling that keeps filling with the house quiet points at a supply or heating pipe. And a stain under a dry loft is its own puzzle, covered in the guide to a ceiling stain when the loft is dry.
If you live in a flat or a converted building, the water may not be yours at all. In that case the guide to a water leak from the flat above covers who is responsible and how to get it stopped.
Why guessing is expensive
The instinct after a collapse is to cut a big hole and look. Sometimes that finds it. Often it finds wet joists and a pipe that runs off in two directions, and the hole gets bigger. Water travels a long way inside a floor void before it drops through, particularly along the fall of old, uneven joists in a granite cottage where nothing is level. The place it appears and the place it escaped can be rooms apart.
A proper survey uses moisture readings to map the wet area across the ceiling and the floor above, thermal imaging to show where a warm heating pipe or a cold supply pipe is sitting against wet material, and where needed a tracer gas or pressure test to prove which pipe has failed. The result is a marked spot and a single small opening, which is exactly what a trace and access claim is meant to pay for. Ripping out a whole ceiling on a hunch is usually not.
Drying out and making good
- Leave the drain holes open and, once you are sure the leak is stopped, keep the room warm and ventilated. Wet plasterboard can take a couple of weeks to dry through; lath and plaster takes longer.
- Do not redecorate until it is dry. Paint over a damp ceiling and the stain comes back within a month.
- Have the electrics checked by an electrician before the circuit goes back on if a light fitting or cable was in the wet area. A fitting that has held water usually needs replacing.
- Keep the wet insulation until the loss adjuster has seen it, if there is a claim, or photograph it thoroughly before it goes.
- Watch for mould on the room side over the following weeks. Coastal Cornish homes in Falmouth, Newlyn or Port Isaac already carry high background humidity, and a wet ceiling can tip a room into a mould problem.
We provide leak detection across Cornwall and a bulging ceiling is one of the most common reasons we are called. The survey report identifies the source, the failed component and the extent of the damage, which is what the insurer needs to move the claim on.
Frequently asked questions
Should I really make a hole in my ceiling?
Yes. A controlled hole at the lowest point drains the water into a bucket and takes the weight off the plasterboard. Leaving it means the water spreads, the board saturates and the whole section is more likely to fall. The hole is easy to patch; a collapsed ceiling is not.
Is it safe to turn the light on to see what I am doing?
No. Switch the circuit off at the consumer unit before anything else and use a torch. A light fitting under a wet ceiling can be live, and the wall switch does not make it safe. Only have the circuit restored once an electrician has checked the fitting and wiring.
How long will it take the ceiling to dry?
Plasterboard often dries in one to three weeks with warmth and ventilation once the leak has stopped. Lath and plaster, common in older Cornish houses, holds more water and takes longer. Do not decorate until a moisture meter shows it is dry, or the stain will bleed back through.
Will my insurance pay for the ceiling?
Most buildings policies cover damage caused by escaping water, which includes the ceiling, decoration and often the floor above. Trace and access cover, where included, pays for finding the leak and making good after it. The repair of the pipe or fitting that failed is normally excluded. Check your own policy wording.
The bulge drained but now it is filling again. What does that mean?
The leak is still running. If the stopcock is off and it still refills, the water is not coming from the mains supply: think heating pipework, a loft tank draining down, waste pipes, rain or a neighbour’s property. Keep the bucket in place and get the source traced quickly.
Ceiling drained, source unknown?
Once the immediate danger is dealt with, we find where the water came from without taking the ceiling down, and give you the report your insurer needs for the trace and access claim.
