Water coming through a ceiling is one of the few household problems where the order you do things in really matters. Get the first ten minutes right and most of what follows is a repair and a drying job. Get them wrong and a plumbing fault can turn into an electrical one, or a stained ceiling can turn into a collapsed one. This guide walks through the first hour in the order we would handle it ourselves, then explains how the source above is actually found.
What should you do first when water is coming through the ceiling?
Deal with the electrics before the water. Ceiling leaks very often find their way to light fittings, because the cable holes in the plasterboard are the easiest route down. Water in a ceiling rose or downlight is a shock and fire risk.
- Do not use the light switch in the affected room, even to turn the light off. Leave it as it is.
- Go to the consumer unit (fuse box) and switch off the lighting circuit that feeds the wet area. If you are not sure which circuit it is, switch off the main switch.
- Only do this if the consumer unit is dry and safe to reach. If water is running near the consumer unit, or you can see signs of water inside it, do not touch it. Keep people away and call an electrician.
- Unplug anything in the room that is near the water, if the sockets and plugs are dry.
- Keep the power off to that circuit until a registered electrician has checked it, even after the leak has stopped.
A torch or phone light is enough for the next steps. It is better to work in poor light than to restore power to a wet circuit.
Is it safe to stay in the room if the ceiling is bulging?
A plasterboard or lath and plaster ceiling that is holding water will sag into a visible bulge. That bulge is heavy. A patch the size of a dinner plate can hold several litres, and wet plasterboard loses its strength quickly. If the bulge is growing, the ceiling can come down without warning.
Keep people and pets out from underneath it. Move furniture, rugs and electrical items out of the way if you can do so without standing directly under the bulge. If the bulge is well away from any light fitting or cable, many plumbers and insurers suggest releasing the water in a controlled way: put a bucket underneath, stand to one side, and make a small hole at the lowest point with a screwdriver. The water then drains into the bucket instead of bringing the ceiling down. If the bulge is near a light, a large section is sagging, or the ceiling is old lath and plaster that is cracking, leave it alone and keep the room closed.
How do you stop a water leak in the ceiling?
You stop it at the supply, not at the ceiling. There is nothing you can do from below that will seal a leak above.
- Turn off the internal stopcock. It is usually under the kitchen sink, in a utility cupboard or where the supply enters the building. Turn it clockwise. In many flats it is in a cupboard in the hallway or near the airing cupboard.
- Switch off the boiler or central heating if there is any chance a heating pipe is involved. On a sealed system, watch the pressure gauge on the boiler. A pressure that keeps falling points towards a heating leak.
- Open the cold taps on the floors above to drain what is left in the pipes, which reduces the amount still able to escape.
- If you have a cold water tank in the loft, closing the stopcock stops it refilling but the tank can still empty through a leak downstream. Some tanks have a gate valve on the outlet you can close.
If the water keeps coming after the stopcock is off and the heating is off, that is useful information in itself. It suggests the water is already sitting in the floor void and draining down, or that the source is not your supply at all: a neighbour above, a roof, or a gutter.
Where is the water coming from?
Once the flow is under control, the question becomes where it started. The pattern of the leak tells you a lot before anyone opens anything up.
| What you notice | Most likely source |
|---|---|
| Leak appears during or just after a shower, stops when nobody uses the bathroom | Shower tray seal, failed sealant or grout, shower valve, or the shower waste |
| Leak appears when a bath or basin is emptied | Waste pipe joint, trap or overflow |
| Steady drip whether or not anything upstairs is used | Pressurised supply pipe, heating pipe or a fitting such as a valve |
| Boiler pressure keeps dropping and the water is warm or discoloured | Central heating pipework or a radiator connection |
| Leak only after heavy or wind-driven rain | Roof, flashing, gutter, flat roof or balcony above |
| Leak when the toilet above is flushed | Pan connector, cistern seal or inlet valve |
A simple test that helps: with the water back on, leave the upstairs bathroom completely unused for an hour and watch the ceiling. Then run the basin, then the bath, then the shower, one at a time, with a gap between each. Note which one brings the water back. That short diary saves a lot of guesswork later.
Why does the leak show up somewhere other than the source?
Water rarely falls straight down. It runs along the top of joists, along pipe runs and along the underside of floorboards or chipboard until it finds a gap. In older London houses with timber floors, it is common for a bathroom leak to appear a metre or two away, sometimes in the hallway rather than the room below the bathroom. In concrete-floored flats, water can track along the slab and appear at a wall junction, around a light fitting or even in a different room.
This is why cutting a hole directly under the stain often finds wet timber and no leak. The stain shows where the water escaped from the ceiling, not where it escaped from the pipe.
Is it different if you live in a flat?
Yes, in two ways. First, the water may not be coming from your property at all. If you are not on the top floor, knock on the door of the flat above straight away and ask them to check their bathroom and kitchen and turn off their stopcock if they can. If nobody is in, contact the managing agent or freeholder, who may have access or an emergency number.
Second, the building insurance for a block is often held by the freeholder rather than by individual leaseholders, which changes who you notify. Check your lease and let the managing agent know early. Our landlord guide to leak responsibility covers how this works when the flat is rented.
How is the source traced without pulling the ceiling down?
A leak detection engineer works from the evidence inward, so that any opening up is small and in the right place. A typical survey combines:
- Moisture mapping of the ceiling below and the floor above, to show the wettest point and the direction the water has travelled.
- Thermal imaging, which shows the cool trail of a cold water leak or the warm trail of a hot or heating pipe. Our thermal imaging service page explains what the camera can and cannot see.
- Controlled flood tests of the shower tray, bath and waste, one fitting at a time, to separate a waste or sealant problem from a pipe problem.
- Pressure testing of the supply or heating pipework, which confirms whether a pressurised pipe is losing water at all.
- Acoustic listening or tracer gas when a pressurised pipe is leaking inside a floor and the point needs to be narrowed down further.
The result should be a marked location and a written explanation of the cause, which is what a plumber needs to repair it and what an insurer needs to consider a claim.
What should you record before you clean up?
If there is any chance you will claim on your insurance, a few minutes of recording now is worth it.
- Photographs and short videos of the ceiling, the drip, the bulge and anything damaged, before you move or throw anything away.
- The time you first noticed the leak and what you did, including when you turned off the water.
- A photo of the water meter reading, if you have one, before and after isolating the supply.
- Anything you notice about when the leak gets worse, as in the diary above.
Most home insurance policies expect you to take reasonable steps to limit further damage, so turning off the water and moving belongings is expected rather than optional. Report the leak to your insurer early and check your own policy wording before arranging any opening up work.
When should you call a leak detection specialist?
If the source is obvious, such as a visibly split pipe in an accessible void, a toilet connector you can see dripping or a neighbour's overflowing bath, you need a plumber rather than a detection survey. Call a specialist when:
- the leak comes back after the water is turned on and nothing upstairs looks wet;
- the upstairs room is tiled and there is no obvious fault;
- the boiler is losing pressure and no radiator or valve is visibly leaking;
- the stain is in a different place from the most likely source;
- you need a written report for your insurer or freeholder.
Our emergency leak detection is priced from £300 to £500, and standard surveys start from £150. Every survey includes a written report. Call 020 3912 0200 to talk it through.
Frequently asked questions
Who should I call for a water leak in the ceiling?
If the leak is heavy and you cannot stop it, call an emergency plumber first. If water has reached lights or sockets, you also need an electrician. If the flow has stopped but the source is unclear, a leak detection specialist will find it before anything is opened up. In a flat, tell the neighbour above and the managing agent as well.
Can I leave water dripping from the ceiling overnight?
Not if you can avoid it. Even a slow drip keeps soaking the plasterboard and the timber above, and a wet ceiling can sag and fail. Turn off the stopcock and the heating, catch the drips, keep the lighting circuit off and get the source looked at as soon as possible.
Will the ceiling need replacing?
Not always. Plasterboard that has been soaked for a short time and dries without sagging can sometimes be kept and redecorated. Board that has bowed, crumbled or stayed wet for days usually needs cutting out and replacing. Lath and plaster ceilings vary a lot, so they need looking at in person once they have dried.
Why does my ceiling only leak when it rains?
That points to the roof, a gutter, flashing, a parapet or a balcony above rather than to plumbing. It is still worth ruling out an overflow pipe or a rainwater pipe running inside the building, which can behave the same way.
Does home insurance cover water coming through the ceiling?
Many buildings policies cover sudden escape of water damage, and some include trace and access cover to find a hidden leak. Leaks from worn sealant or grout, or damage that built up slowly, are often treated differently. Policies differ, so check your own wording and see our guide to leak insurance claims.
