Only when the shower runs, or all the time?
A shower leaking through the ceiling below usually comes from one of four places: the seals around the tray or screen, the waste under the tray, the grout and tiles, or a pipe feeding the shower. Timing narrows it down fastest. A stain that appears or darkens only after someone showers means water escapes while the shower is used. A stain that keeps spreading on a day with no showers points to a pipe that is under pressure all the time.
Keep a simple log for a few days. Draw a light pencil line around the edge of the stain, note who showered and for how long, and look at the line again the next morning. Some leaks only show after a long shower, on a powerful setting, or when someone aims the head at one wall. If the stain spreads while nobody uses the shower, close its isolating valves if it has them, or the stop tap, and ring for help.
Shower leaking through the ceiling: the usual sources
With an upstairs shower leaking through the ceiling, water has found a gap between the wet area and the floor. The silicone line between tray and tiles is often the first thing to fail: it shrinks, peels or blackens, and water runs behind the tray. Cracked grout lets water soak into the wall behind, especially where older tiling sits on plasterboard. A screen or door with a worn bottom seal spills water onto the bathroom floor, and it finds a way down past the tray edge.
A leaking shower waste is another frequent cause. The waste is the outlet and trap under the tray, and its joints can work loose if the tray flexes, which can happen when a tray was never bedded on a firm, flat base. Behind the tiles, the mixer valve and its pipe connections can weep, sometimes only while the shower is running. Now and then the real source is a pipe passing under the bathroom floor to another room, and the shower just happens to sit above it.
Tray seal: stain after every shower, worse after a long one
Grout or tiles: stain grows when water hits the walls
Screen or door: puddles on the bathroom floor beside the tray
Waste: drips start soon after the water has gone down
Supply pipe: stain spreads even with the shower off
A sequence you can try before anyone visits
Test one part at a time, with a day between tests. Mark the edge of the stain in pencil before each one, so you can see whether it spreads, and ask someone to stand below with a torch. Give each test about 10 minutes, and stop straight away if water appears downstairs. Use a jug or the hand-held head rather than buckets, so you control exactly where the water goes.
Each step wets one part of the shower and keeps the rest dry, so a fresh drip or a stain that creeps past your pencil line points to the part you have just tested. Write down what happened after each step, and when. Your notes tell whoever comes out which part to look at first.
First: pour water slowly into the waste from a jug, keeping tray and walls dry
Second: hold the head low and run water into the tray only
Third: spray the tiled walls and the silicone corners
Fourth: shower normally with the door shut, then check the floor outside it
Last: leave the shower off for a full day and check the stain
Why tiles come off for nothing
Water rarely drops straight down. It runs along joists, pipes and the back of the ceiling board before it finds a way through, so the stain below can sit well away from the leak above. A tiler who lifts the tiles above the stain can find a dry wall behind them, and a fresh bead of silicone does nothing for a loose waste. That is how a shower can be resealed twice and still drip onto the kitchen table.
Tired grout is not proof either. Plenty of shabby showers are watertight, and plenty of neat new ones leak at the waste. Before anything is broken out, ask for the source to be shown by testing. Then the wall or tray is opened where the fault is, and only as far as the repair needs.
How the leak is found
A visit starts in the room below. We take moisture readings in a grid across the ceiling, and the numbers trace the outline of the wet plaster and its wettest point, which usually says which corner of the shower to test first. Upstairs, each part is tested in turn, much like the sequence above but with readings before and after each test. Thermal imaging shows where water is moving behind tiles or under a tray, because wet areas show up at a different temperature from dry ones.
Our engineer Charlie only marks and photographs a spot once two different tests have picked it out, and the tiles stay on while the testing is done. In a flat, the testing usually has to happen from the flat above as well. If you live downstairs, the owner upstairs, or their managing agent, will need to agree to that access. If any pipes cross into a neighbour's property, mention it when you ring.
What affects the cost of putting it right
What an upstairs shower leaking through the ceiling costs to sort out depends far more on the failed part than on the size of the stain. Resealing a tray is a small job. A waste that needs replacing means getting underneath the tray, which is easy behind a removable panel and much harder on a tray that is tiled in or set on a solid base. A valve or pipe behind tiles means opening the wall at one marked spot and retiling it.
Then come the knock-on jobs: the ceiling below patched and painted, wet boards or joists dried or replaced, and matching tiles found for any that break. The price for tracing the leak is agreed with you before you book, and it is not reduced if the leak is found quickly. Where the fault is on pipework, we can usually repair it. That repair is quoted separately and guaranteed for 3 months on the pipework and fittings we install.
No find, no fee on home water leaks covers one leak on a water main up to 30 m or the hot and cold supply pipes, at least half a litre a minute, where we also carry out the access and repair. A tray seal, grout or a shower waste is not a supply pipe, and a leak that shows only while the shower runs comes and goes, so neither falls under it. Full conditions are on our terms page.
Insurance and the report
Ring your insurer before any tiles come off. Two questions are worth asking: does the policy pay towards trace and access, and does the insurer need to say yes before work starts? Some policies exclude damage from worn grout or sealant, so read the wording rather than guess. Photograph the stain, your pencil lines and any wet flooring now, because a dried-out ceiling leaves little behind to show anyone.
Our written report gives the location, methods, readings and photographs, and it is released when payment for the visit is complete. If water is coming into your flat from the one above, the report shows where we traced the water to, which gives both households, and both insurers if they are involved, the same facts to work from. Whether any claim is paid is always for the insurer to decide.