Do this first
- Electrics before water. If water is anywhere near a light fitting, a downlight or a ceiling rose, go to the consumer unit and switch off the lighting circuit for that floor, or the main switch if the labelling is unclear. Do not flick the light switch to test it, and do not stand under a fitting that is dripping.
- Clear the space underneath. Furniture, rugs, anything electrical, anything that stains. Then buckets and towels.
- Close the internal stopcock. It is usually under the kitchen sink, in a downstairs cloakroom, or near where the main pipe enters the house. Then open the kitchen cold tap and leave it running until it dies to a trickle, which empties the rising main so it stops feeding the leak.
- Switch the heating off as well. A sealed heating circuit holds its own water and keeps leaking after the stopcock is shut. Turning the boiler off stops the pump pushing it out.
- If it is coming from the flat above, knock and ask them to close their stopcock and turn their boiler off. If nobody answers, contact the managing agent or freeholder rather than forcing entry.
- Photograph it before you mop. A wide shot of the room, close-ups of the ceiling, and the time on your phone. That is the evidence an insurer asks for later.
If the ceiling is bulging, drain it deliberately
A bulge is a pocket of water lying on the back of the plasterboard. Saturated board is heavy, and when it lets go it comes down in a sheet with whatever was resting in the void above it. Draining it on purpose is safer than waiting for it.
- Put a bucket directly under the lowest point of the bulge.
- Stand to one side of it, never underneath, and wear eye protection.
- Reach in at arm's length and pierce that lowest point once with a screwdriver.
- Let it drain. Do not widen the hole or add more. One hole at the low point empties the pocket.
Do not do this if the ceiling is lath and plaster rather than plasterboard, because older London ceilings with a fibrous, uneven back fail in whole sections instead of at a hole; if the ceiling carries a textured coating such as Artex and the building was put up or last refurbished before 2000, because those coatings can contain asbestos and piercing one makes dust; if the sag is wide, cracked, or already dropping at its edges; if water is still pouring in and nothing has been isolated; if there is a light fitting in or beside the bulge and the circuit is still live; or if you would need a ladder to reach. In any of those cases, shut the door on the room and leave it.
What it usually is, and the test that separates them
Where the stain shows tells you very little about where the leak is. Water runs along the top of a joist until it finds a screw hole or a board joint, so the wet patch can sit a couple of metres from the source. Timing is what narrows it down.
| When it wets | What it usually is |
|---|---|
| Only while a shower or bath runs or drains | Tray, bath seal, waste or overflow in the room above |
| Constantly, with nobody using anything | A pressurised pipe: the cold main or a heating pipe under the floor above |
| Only during and after heavy rain, top floor | Roof, flashing, chimney or a blocked gutter, not plumbing |
| Only when a washing machine or dishwasher pumps out | Waste connection or standpipe behind the appliance |
| A ring that dries out between uses of one WC | Pan connector, or the waste below it |
Two checks settle the constant case. Turn everything off, read the water meter, wait half an hour without using a drop, and read it again: movement means a live leak on your side of the meter. If the boiler pressure gauge is falling as well, the loss is on the heating circuit rather than the cold main. Both tests are set out step by step in our guide to the first ten minutes of a ceiling leak.
What the repair involves
Once the source is confirmed, the pipe or fitting is isolated and repaired properly rather than clamped. On a copper run that usually means cutting out the failed section and soldering or press-fitting a new piece; on a push-fit joint it means replacing the fitting and checking the pipe insert; on a shower tray or bath it means stripping and rebedding the seal or renewing the waste.
The ceiling is the other half of the job and we do it in-house. Saturated plasterboard does not dry back to flat, so the blown area is cut out to the nearest joists, the void is dried, new board is fixed, taped and skimmed, and the ceiling is repainted wall to wall rather than patched, because a patch always shows. Where the ceiling is lath and plaster, or carries a coating that needs testing before anyone disturbs it, we say so before work starts. That is the ceiling leak repair job end to end, and what we charge for it is on the pricing page.
When it is not us
- Water in a light fitting. The leak is ours, but the fitting is not. Once the water is stopped, an electrician should test the circuit and replace anything that has been wet before it goes back into service. Do not re-energise it yourself on the basis that it looks dry.
- Rain-driven stains on a top floor. Roof, flashing, gutter or parapet, which is a roofer, and in a block it is the freeholder's structure rather than yours.
- A communal pipe, a soil stack or the roof in a block of flats. That is block management. Report it in writing and keep the reference.
- You rent. Tell the landlord or agent immediately and in writing. Installations for the supply of water and for sanitation are the landlord's to keep in repair.
- Black mould in a cold corner with no water history. That is condensation and ventilation, not a leak, and a detection visit will only confirm what a dry meter reading already tells you.
- Damage rather than cause. The ceiling, the floor below and your contents go to your insurer as an escape of water claim. What you want from us is the written report that proves where the water came from. See a leak coming from the flat above and our insurance claims hub.