Water Coming Through the Ceiling: The First Ten Minutes

Minute by minute

1. Everyone out from underneath. A wet plasterboard ceiling holds water in a pocket, and the pocket gets heavier every minute. Move people, pets, and anything you would mind losing.
2. Electrics, before water. A ceiling void is full of cables, and the light fitting in the middle of it is the lowest point water will find. If water is at or near a ceiling rose, a downlight, or running down a wall with sockets, switch the supply off at the consumer unit — but only if the fusebox is dry and you are not standing in water. Electrical Safety First is explicit: turn it off at the fusebox only if it is safe to do so, and do not touch exposed wiring. Use a torch, not the light switch.
3. Now the water. If the leak is yours, shut the internal stop tap clockwise, open every cold tap and flush the toilets. If it is coming from the flat above, your stop tap does nothing — theirs is the one that matters. Knock hard. No answer means the managing agent, and in a block there is usually an isolation valve on the riser for that flat.
4. Catch and contain. Buckets under the drips, a plastic sheet or a bin bag split open over furniture that cannot move, towels round the edges. Lift electricals off the floor rather than mopping round them.
5. Deal with the bulge. Below.
6. Photograph before you tidy. Wide shot of the room, close shots of the ceiling, a short video with the water actually running. Then start clearing up.

The bulging ceiling, which most guides leave out

A sagging patch of ceiling is a bag of water. Plasterboard soaked through loses most of its strength, and the paint or paper skin on the underside is often the only thing holding the load. Water weighs a kilogram a litre, and a modest bulge can be holding several. When it goes, it does not go politely: the board, the water, and whatever is in the void above — loft insulation, decades of dust, sometimes a light fitting — all arrive at once.

Draining it deliberately is safer than waiting. Done properly it looks like this:

1. Clear the floor underneath completely and put a bucket, or a bath sheet in a washing-up bowl, directly under the lowest point of the bulge.
2. Confirm the electrics to that area are off, and that there is no light fitting in or beside the bulge.
3. Stand to the side, at arm's length. Never directly underneath. Eye protection if you have any, because what comes out is gritty.
4. Make one small hole at the lowest point with a screwdriver, and pull the screwdriver back out of the way.
5. Let it drain. Empty the bucket and wait. Enlarge the hole slightly only if the flow stalls while the bulge is still full.

When not to do this. Leave it alone and get people out of the room if the ceiling is old lath and plaster and already cracked across a wide area, if the bulge surrounds a light fitting or downlight, if the ceiling is already dropping at the edges, or if you cannot clear the floor underneath. Also leave it if you cannot reach the lowest point without standing on something unstable — falling off a chair is the more likely injury here than anything the ceiling does.

Piercing a ceiling does not make the insurance claim worse. Letting it collapse over a room full of furniture does.

Where it is actually coming from

The wet patch is almost never under the leak. Water runs along joists, along cable runs and along the top of the plasterboard until it finds a screw head, a joint or a light fitting, so the stain can be metres from the source. That is why lifting the boards above a stain so often finds nothing.

Pattern	Usual source
Only when the shower above runs	Shower tray, waste, or the seal where the tray meets tile. A shower leaking through the ceiling is the most common of all of these.
Only when the bath is used or emptied	Bath waste, overflow, or the sealant line.
Constant, day and night	A pressurised pipe. Cold mains or a heating pipe, and the one that needs the water off now.
Worse when the heating runs	Heating pipework or a radiator tail in the floor above.
Only after heavy rain	Roof, flashing, a blocked gutter or a parapet. Not a plumbing job.
Brown and smelly	A soil pipe or a waste run. Treat as contaminated and wear gloves.

When this is not a plumber

• 999 if a ceiling is coming down on a room you cannot clear, if anyone is hurt or trapped, if there is arcing, smoke or a burning smell near the electrics, or if you smell gas at the same time.
• Your electricity network operator if the consumer unit itself is wet and you cannot reach it safely to isolate.
• A Gas Safe registered engineer before any gas appliance that has been rained on from above goes back into use. Water gets into gas valves and controls and the damage is not visible from outside.
• The managing agent or freeholder if the source is a communal riser, a roof, or a flat whose owner cannot be reached.
• A roofer if it only happens when it rains.

Once the water is off

Do not open the ceiling looking for the pipe. On a leak from above, the source is found from the floor above wherever possible — moisture mapping across the floor, thermal imaging along the pipe runs, and a pressure test to confirm whether it is a pressurised pipe at all or a waste that only leaks in use. That is the difference between one small opening and a ceiling taken down across a room.

The part we do that detection-only firms do not is put it back: board, skim, paint. Ceiling leak repair covers the whole sequence, and trace and access is usually the part of the policy that pays for it. Our rate is £150 per hour, agreed before we attend, and if we cannot find the leak you do not pay for the time we spent looking.