What to do in the next ten minutes
- Switch off the lighting circuit serving that room at the consumer unit. Water in a ceiling void runs along joists and cables and arrives at ceiling roses and downlights, because those are the holes. Do this before anything else.
- Drain a bulge, do not wait it out. A sagging plasterboard ceiling is holding several litres and will come down as one sheet. Pierce it once at the lowest point of the bulge with a screwdriver, standing to the side, with a bucket underneath. You will usually save the board and you will definitely save the floor.
- Move what is underneath and get a sheet over the rest.
- Find out whether it is still running. Press the stain. Soft, cool and spreading means the leak is live. Hard, dry and sharply ringed means it stopped some time ago and you have a decorating problem rather than a plumbing one.
- If the water is coming from a flat above, tell them now and ask them to stop using the bathroom and the kitchen until someone has looked. That single request stops more damage than anything else you can do.
- Photograph it wet. Insurers assess evidence, and it dries.
More on the immediate steps at water coming through my ceiling.
The stain is not the leak
Water enters a ceiling void, lands on the top of the plasterboard or on a joist, and then travels — along the joist, along a cable, along the top of a wall plate — until it reaches the first downward path. That path is a light fitting, a board joint, or a nail hole. The result is that the wet patch is very often a metre or more from the actual defect, and sometimes in a different room. Opening the ceiling under the stain is the mistake that turns one small repair into three.
So the first job is to work out what is above it, and that comes down to a short list.
What we find above London ceilings
| What is above | Usual cause | Tell-tale |
|---|
| Bathroom in the same property | Shower tray seal, waste connection, bath overflow, or the concealed valve and pipework in the wall | Wets only during or just after use, or only when the bath is drained |
| Bathroom in the flat above | The same four faults, one floor up, plus a failed grout or seal letting water past the tiles | Wets on their schedule, not yours |
| Kitchen above | Washing machine or dishwasher hose, the trap under the sink, or the supply tails behind the units | Appears during a cycle, or constantly if it is a supply connection |
| Heating pipework in the void | A pinhole or a joint on a horizontal run crossing joists, often added during a conversion | Boiler pressure dropping, worse when the heating runs |
| Boxed-in soil stack | Split or unsealed joint in the stack, or a branch connection | Only wets while something upstairs drains; often discoloured or smelling |
| Flat roof, parapet or valley gutter | Not plumbing at all | Appears with rain, dries between |
| Top-floor flat under a shared roof | Roof, parapet or a blocked hopper, and a freeholder responsibility | Rain-linked, and often affects several flats |
That last pair matter. If your ceiling only wets when it rains, no leak detection engineer is going to find anything, and we will tell you that rather than charge you to look. The related symptom pages go further: a shower leaking through the ceiling, a leak from the flat above, and a water stain that may or may not be live.
How the visit runs
- Read the ceiling. Moisture mapping across the whole ceiling, not just the stain, to establish the extent and the high point of the wet zone.
- Work out what is above it, from the layout, the joist direction and the position of the pipework. Joist direction decides which way water has travelled.
- Isolate and test. Hot, cold and heating pressure-tested in turn. A ceiling that stays dry with the heating isolated and wets when it is restored has told us a great deal in half an hour.
- Run the fixture tests if a bathroom is above: fill and stand the bath, then drain it; run the shower with the waste blocked, then unblocked; flood the tray edge; flush the WC. Each of those isolates a different component, and they are done in an order that does not contaminate the next test.
- Thermal imaging and tracer gas where the tests have not separated the candidates, or where the pipework is concealed in a wall or screed.
- Open one access point, from below where the ceiling is already damaged, or from above through the floor where the ceiling is sound and worth keeping.
- Repair, test at pressure, then reinstate.
Repairing the ceiling, not just the pipe
This is where we differ from almost everyone else in this market. A detection firm will find the leak and leave you with a hole and a damp ceiling. We have builders and handymen in-house, so the ceiling is part of the job.
What that means in practice depends on the ceiling. Modern plasterboard: cut back to the joists, new board, taped, skimmed and decorated. Victorian lath and plaster: the decision is repair or overboard, and it is a real decision — a sound lath ceiling with a localised failure can be patched and re-skimmed, but plaster that has lost its key across a wide area will keep dropping and is better overboarded and skimmed as one plane, which also gets you a flat ceiling instead of a patched one. Coving and cornice: period profiles can be run or cast to match rather than replaced with a modern stock section. Textured coatings on older ceilings are treated as presumed to contain asbestos until it has been established otherwise, so we do not sand or break them up as a matter of course.
And it does not get painted until it is dry. A ceiling that is skimmed over damp board will bloom, and a stain that is painted before it is sealed bleeds back through within weeks. Drying, then a stain-block, then paint.
When the leak is in someone else's flat
This is the most common ceiling leak in London and the most frustrating, because the damage is yours and the pipe is not. Three things move it along. First, get the source identified and written down, including the date, the extent, and the mechanism — that document is what both insurers work from and what a managing agent acts on. Second, keep your own evidence: photographs while wet, and readings. Third, remember that the escape of water and the trace and access are usually treated as separate parts of a buildings claim, and that the flat above's insurer and yours may both be involved. We can attend your flat, map the water and produce the report even when the repair itself has to be carried out upstairs. There is more detail under insurance claims and trace and access.
Terms
£150 per hour, fixed before we attend and the same for an evening or weekend visit. The total depends on how long the job runs and what materials go into the reinstatement; the rate is the part we can commit to in advance, and we do. No find, no fee on the detection. Written report prepared for a trace and access claim. The pricing page sets out how the hours are counted.
