The flat middle of a bathroom floor is the easy part. Almost every wet-area leak starts at a hole — the floor trap, a waste pipe, a sleeve — and this is how that detail is built, tested and rebuilt.
Every wet area in a Malaysian home has holes deliberately cut through its floor slab. The floor trap — the grated outlet in a bathroom, yard or wet kitchen — is the largest of them. Around it sit smaller ones: the waste pipe from the basin, the soil pipe from the water closet, sometimes a sleeve carrying a supply pipe or an air conditioning drain down to the floor below.
Each of those holes is a deliberate breach in the one continuous surface that is supposed to keep water out of the structure. A tiled floor is not waterproof — tile is, but the grout between tiles is not, and water passes through grout into the bed beneath it as a matter of routine. The layer that actually stops water is the membrane buried under the tiles, and its job at a penetration is to stop being a flat sheet and become a funnel: it has to run down into the trap and terminate inside the drainage path rather than beside it.
That is why penetrations are where wet-area floors leak. The flat middle of a bathroom floor is the easy part. Every failure we open up is at an edge, a corner or a hole.
Read a wet-area floor from the bottom up and the logic of the detail becomes obvious.
Get that sequence right and it does not matter that the grout is porous, because everything that gets through it lands on a membrane that funnels it into the trap. Get it wrong at the trap and the same water lands on a membrane that stops short, runs sideways under the tiles, finds the annulus around the trap body and goes through the slab.
These are what we actually find when a floor is opened up around a trap:
| Failure | What it looks like when opened | What the repair has to do |
|---|---|---|
| Membrane stopped short of the trap | Coating simply ends on the screed a few centimetres from the trap collar | Take the membrane into the trap body and terminate it inside the drainage path |
| Trap bedded in ordinary mortar | A hairline gap all the way round the trap body where the mortar shrank away | Cut out, re-bed in non-shrink grout, then re-detail the membrane over it |
| Pipe sleeve packed and skimmed only | Rubble and a smear of cement round the pipe; no sealant, no collar | Rake out, fill properly, form a collar and dress the membrane up onto the pipe |
| Trap set too high | The floor holds a puddle after washing down instead of draining clean | Reset the trap level or re-lay the screed falls — not a sealant job |
| Trap replaced during a later retile | New tiles, new trap, original membrane cut through and never reinstated | Re-detail the membrane at the new trap; a retile is not a re-waterproof |
| Cracked trap body | A split in the plastic, often at a fixing or from an impact | Replace the trap, then rebuild the membrane detail around it |
| Silicone used as the seal | A bead of sealant around the trap collar doing the membrane’s job | Remove it; sealant is a joint filler, not a waterproofing termination |
Send us a photo of the job on WhatsApp — we reply with an instant quote.
💬 Get Your Instant QuoteFive of those seven are decisions made during construction or a previous renovation, which is why the problem so often appears in units that have never obviously been damaged. The last one is the most common DIY response and the most misleading, because a fresh silicone bead genuinely does stop the drip for a few weeks.
The unit below almost always sees it first. Three characteristics separate a trap penetration leak from the alternatives.
Position. The stain sits directly under the trap or slightly to one side of it, and it is usually compact rather than spread across a whole ceiling. Water that has crossed a slab tends to run along the underside until it finds a low point, so a small offset is normal, but a stain three metres away is telling you something else.
Timing. It responds to use. The ceiling darkens after the bathroom above is used, and then dries back between times — a cycle rather than a constant. A leak that drips steadily day and night, including while the unit above is empty, is a pressurised supply pipe, not a trap.
Character. Slow weeping through concrete rather than a running drip: a damp patch, a bulge in the plaster, a brown edge to the stain as it dries. Where it has been going on for a long time you may see a chalky lime crust or a small deposit forming, which is the same mechanism described in our efflorescence guide.
For the broader menu of ceiling stains and what each one means, water stains on the ceiling is the diagnostic page, and upstairs bathroom leaking through the ceiling covers the case where the bathroom above is the obvious suspect.
Three problems produce a wet ceiling under a bathroom, and they have three different repairs. Getting this wrong is how people pay for a full hack and retile to fix a leaking waste connection.
| Trap or sleeve penetration | Membrane failure across the floor | Waste pipe or joint | Supply pipe | |
|---|---|---|---|---|
| When it wets | After the floor is used or washed down | After the floor is used, especially the shower area | Only while that fixture drains | Continuously, even with the unit empty |
| Where the stain sits | Under or beside the trap, compact | Under the wet zone, more diffuse | Along the pipe run below | Anywhere along a concealed run; often spreading |
| Water meter with everything off | Still | Still | Still | Creeping or spinning |
| Ponding test with the trap plugged | Usually stays dry — water is not reaching the fault | Wets the ceiling below | Stays dry | Irrelevant — wets regardless |
| Water run into the trap only | Wets the ceiling below | Stays dry | Wets, if the fault is downstream | Irrelevant |
| Usual repair | Local rebuild of the penetration | Re-waterproof the floor | Expose and remake the pipe joint | Detect, then repair or re-route |
If the meter moves with every tap closed, stop reading this page — you have a supply leak, and concealed pipe leak detection is where to go. If the whole shower area wets rather than the trap surround, shower floor leak repair is the closer match.
These are cheap, they are non-destructive, and between them they usually name the fault before anyone lifts a tile. Do them in this order and have someone watching the ceiling below on each one.
Where the ceiling below is already open or accessible, a moisture meter comparison against a dry part of the same ceiling makes the readings sharper. Where nothing conclusive shows, a proper detection visit adds acoustic and thermal tools to the same logic — water leak detection explains what that visit involves.
If you are paying for the local rebuild, this is the sequence the work should follow, and it is a fair checklist to hold a contractor to on site.
Tiles come up in a defined zone around the trap, wide enough to land the new membrane on sound existing material rather than finishing on a broken edge. The screed is cut back to something solid. The trap is checked for cracks and for movement; if it moves at all, it comes out and is re-bedded in a non-shrink grout rather than being sealed in place. Pipe sleeves in the zone get the same treatment — raked out, filled, and given a collar so the membrane has something to turn up onto rather than dying against a bare pipe. The prepared surface is primed. The membrane goes on in the specified number of coats, with reinforcing tape at the wall junction and at any corner, turned up the wall behind where the tiles will go, and taken down into the trap body and clamped or terminated inside it. Then the falls are reinstated so the patch drains into the trap rather than away from it, and only then does the tiling go back.
Two details are worth watching for personally, because they are the ones most often skipped: whether the membrane genuinely enters the trap rather than stopping at its collar, and whether the reinstated screed still falls to the trap after the patch is made good. Ask for photographs at each stage. Any competent crew will take them without being asked twice.
A wet-area repair that has not been tested is an opinion. The test is simple and there is no reason to skip it: after the membrane has cured for the period its manufacturer specifies, plug the trap, flood the floor to a shallow even depth, mark the water level, and leave it for twenty-four to forty-eight hours with somebody checking the ceiling below. A drop in the marked level, or any dampness appearing downstairs, means the repair is not finished.
Run the trap-only test as well once the ponding test passes, because a ponding test with the trap plugged does not test the trap. Then let the floor dry properly before the tiles go down, and after tiling do one final check: pour a bucket across the floor and watch it reach the trap. If it puddles, the falls were not reinstated, and a floor that holds water will find the next weak point sooner than one that drains. Our guide to how long waterproofing lasts covers what to expect afterwards.
Repairing the leak and repairing the damage are two jobs with two budgets, and the second one cannot start until the first is proven. Painting a ceiling that is still drying traps moisture behind the film and the stain comes straight back through.
The sequence downstairs is: stop the water, then let the ceiling dry out completely — which takes longer than people expect, because a concrete slab holds moisture and gives it up slowly — then cut out and replace any plasterboard or skim that has blown or crumbled, then apply a stain-blocking primer so the old tannin marks do not bleed through the new paint, and only then decorate. Ceiling leak repair covers that side in detail.
Where the leak crosses between two separately owned units, the practical questions of access, evidence and who pays are handled on inter-floor leakage. Keep dated photographs, the results of each test above, and any written correspondence from the beginning — it is far easier to keep that record than to reconstruct it.
These are ClickBina’s own published prices for the repairs a trap leak most often leads to:
| ClickBina service | ClickBina price | What it covers |
|---|---|---|
| Leak detection & assessment | RM300 – RM800 per visit | waived if you proceed with the repair |
| PU injection — leaking bathroom ceiling | RM650 flat | one bathroom ceiling, includes the injection points |
| Bathroom re-waterproofing (non-hacking) | RM1,500 – RM3,500 per bathroom | existing tiles stay; coating over the screed |
| Bathroom re-waterproofing (hack & retile) | RM4,500 – RM9,000 per bathroom | tiles off, new membrane, retiled |
PU injection is quoted flat per bathroom ceiling here rather than per injection point, which is worth knowing because the market convention is to charge per point (market estimate 2026, indicative Klang Valley):
| Repair | Market range (2026, Klang Valley) | Notes |
|---|---|---|
| PU injection, market rate | RM80 – RM250 per point | priced per injection point, not per room |
On a point-priced quote the number of points is the variable, and it is set by the contractor after they arrive. That is not dishonest — it is simply a structure where the final figure is not known when you agree to the work.
Where the answer is re-waterproofing the floor rather than injecting the slab, these are the market bands per square foot (market estimate 2026, indicative Klang Valley), with the third column showing a 40 square foot bathroom or yard floor:
| System | Market range (2026, Klang Valley) | 40 sq ft floor |
|---|---|---|
| Cementitious slurry | RM6 – RM10 per sq ft | RM240 – RM400 |
| Flexible two-part membrane | RM8 – RM14 per sq ft | RM320 – RM560 |
| Liquid PU membrane | RM10 – RM18 per sq ft | RM400 – RM720 |
Those bands cover supply and application of the membrane only. Hacking, removing and reinstating the trap, screed, tiling, making good and the ceiling below are separate lines, which is exactly why the whole-job prices in the first table are the more useful comparison. The full menu is on waterproofing services, and bathroom waterproofing cost breaks the bathroom case down further.
Insist the quote states: which test led to the diagnosis and what it showed; the extent of the tile removal in square feet or by a marked plan; whether the trap is being reset or replaced and with what type; how the membrane is terminated at the trap; the number of membrane coats and where reinforcing tape is used; whether the screed falls are being reinstated; the curing period before tiling; whether a ponding test and a trap-only test are included and for how long; the making good above and below; and the disposal of debris.
Then ask: Is the membrane going into the trap, or up to it? How will you prove the floor still falls to the trap when you are finished? What is your ponding test duration and can I see it running? If this leaks again after the test passes, what is the process? How many days will the bathroom be out of use? A crew that answers all five without hedging is a crew that has done this before. Questions to ask a waterproofing contractor has the wider list.
ClickBina repairs trap and penetration leaks across Kuala Lumpur and Selangor, and we test before we quote. The meter test, the ponding test with the trap plugged and the trap-only test cost us an afternoon and they decide whether you are buying an injection, a patch around one trap or a new bathroom floor — a difference of thousands of ringgit. When we do open a floor, the membrane goes into the trap body, the falls are reinstated and checked with water rather than with a level alone, and the ponding test runs with you able to see it. Detection is RM300 – RM800 per visit and comes off the job if you proceed with us. Send photographs of the stain below and the trap above on WhatsApp and we will tell you which test to run first.
Tell us what you need — we reply within the hour.