A damp patch on the wall next to the bathroom is a worrying thing to find. So is a skirting board that has started to swell, or a musty smell in the wardrobe. A shower leaking into the next room can cause all of these. It is not the only possible cause, though. Before anyone retiles or regrouts, it pays to know where the water is really coming from.
Why does a shower leak show up in the room next door?
Water does not always show where it gets in. It often travels a long way inside a wall or floor before you can see it. So the stain is not always beside the fault.
The room beside the shower can be where the water shows. That is how you can end up with a shower leaking into a bedroom wall, a hallway or a built-in wardrobe. If the shower is upstairs, the leak may show on the ceiling below instead.
What keeps the water inside a shower?
Under the tiles sits a membrane (a waterproof layer). The membrane is the only waterproof layer in the shower. Tiles and grout are porous (they let water soak in). They always let some water through, and the system is designed on that basis.
So when shower waterproofing fails, the problem is under the surface, where you cannot see it from inside the shower.
Where do shower leaks usually come from?
In wet areas, the details most often missed are at the edges. None of these can be seen once the tiles are on. That is why a leak can appear months or even years after the bathroom was finished. Places worth knowing about include:
- The hob or door threshold. The hob is the raised edge or step at the shower entry. A membrane that stops short here can let water out under the tiles.
- The junction where wall meets floor. If this joint was not treated, water can get through the corner.
- The fall of the floor. Fall is the slope that carries water to the drain. A floor with no fall can let water pool against a wall.
- The waste (the shower drain). The membrane has to be joined to the drain, often at a fitting called a puddle flange (a collar that links the membrane to the drain).
- Taps, mixers (the tap that blends hot and cold water) and the shower rose (the shower head). These pass through the waterproofed wall, so the seal around them is a common place for water to get behind the tiles.
- The shower screen. Water can find its way past the screen and out of the shower.
- A water pipe inside the wall. This is a plumbing fault, not a waterproofing one.
What are the signs of a leaking shower?
Some signs of a leaking shower are easy to miss. Look for:
- A swollen skirting board next to the bathroom, or one pulling away at the bottom.
- Flaking or bubbling paint, or a stain on the wall beside the shower.
- Fresh paint in only the room beside the bathroom.
- A musty smell in a built-in wardrobe that backs onto the bathroom.
- Drummy tiles (tiles that sound hollow when tapped).
- A leak that keeps coming back after repairs.
- Water bills that rise for no clear reason.
Timing gives a useful clue. Damp that shows in the next room only after the shower is used points towards the shower itself: the waterproofing, the screen, the waste or the seals around the taps. Damp that shows even when nobody has used the shower points towards a water supply pipe under pressure. These are patterns, not answers. Testing is what confirms the cause.
Could the damp wall be something other than the shower?
Yes. A damp wall next to a bathroom can have other causes, or more than one cause at the same time.
- Condensation is a real problem in poorly ventilated Queensland bathrooms. It tends to show as black, spotty mould. It is worst in corners and high on walls or ceilings, not at the base of the wall.
- Rising damp is common across the Gold Coast and coastal Brisbane. It affects ground-floor walls. It is worst at the base of the wall, with a fairly level tide mark (a line on the wall where the damp stops), and often comes with salt deposits and blistering paint.
On a ground floor, a shower leak and rising damp can look alike. You still need to know which cause you have, or whether you have both. Salt in a wall can also make a dry wall read wet on a moisture meter, so a single reading can mislead. Our guide to rising damp, lateral damp and condensation explains how to tell them apart.
Why is my regrouted shower still leaking?
Because the grout was never the waterproof layer. Sealing grout slows water getting into the tile bed (the layer the tiles are stuck down on), but it does not stop it. If the membrane underneath has failed, the shower still leaks, just more slowly. Meanwhile water trapped under the tiles keeps the area wet.
New grout or silicone (the flexible sealant along corners and edges) is cheap and quick. It can make an older shower look fixed while the wall next door stays damp. A regrouted shower still leaking points towards water getting past something deeper, such as the membrane. The same idea is explained for balconies in our article on why the tiles are not the problem.
How is a shower leak found without pulling the bathroom apart?
Shower leak detection works by building up evidence step by step. HydroIQ's leak source identification combines thermal imaging, moisture detection, pressure testing and dye testing. Water or dye testing is used where needed to confirm the source. In shower terms, it looks like this:
- History first. When did it start? Does it follow showers, rain or neither? What has been repaired, repainted or renovated? Any plans, certificates or earlier reports help too.
- Thermal imaging. A thermal imaging camera (a camera that shows surface temperature) can show damp patterns the eye cannot see. It does not see water, so a thermal image is a lead to check, never a finding on its own.
- Moisture mapping. Readings are taken on a grid across the wall or floor and compared with a known dry area of the same material. The pattern of where it is wettest, and how it fades, points towards the source.
- Controlled water testing. Water is run over one suspect part at a time, in a set amount for a set time, while the damp spot is watched. The shower screen, for example, can be tested on its own. This step is slower, and it is where most of the certainty comes from.
These methods are non-destructive (they do not damage the bathroom). Now and then, a small inspection opening is the only way to confirm a finding. If so, it is discussed with you first and kept to the minimum. Our article on how a waterproofing investigation works explains each step in more detail.
What should I check and ask before anyone retiles?
- When did you first notice the damp, and has it grown?
- Does it appear only after showers, or also when the shower has not been used?
- Has the shower been regrouted, resealed or repainted around? When?
- When was the building approval issued? This decides which edition of the standard applies.
- Do you have a waterproofing certificate? It shows the installer certified their own work at the time. It is useful evidence, but it does not prove the membrane was put in correctly or still works.
- Is the home newer? If so, check the current Queensland Building and Construction Commission (QBCC) complaint time limit straight away.
In Queensland, the National Construction Code (NCC) points to Australian Standards such as AS 3740 as the accepted way to meet its waterproofing requirements. Check the current edition of both. An independent investigation also protects you from blaming the builder for a leak that turns out to be a blocked drain or a plumbing fault.
Who does what?
HydroIQ investigates and reports. We do not carry out repairs, which keeps our findings independent. An investigation is a paid service.
A useful report sets out what was seen, measured, tested and concluded, with photos and readings. It names the standard where one applies. It states where the water gets in and the likely cause, how far the damp has spread, and what was not found. It also says what needs fixing, in terms a contractor can price and plan from.
The repair itself is work for a licensed contractor. If the fault is a leaking water pipe in the wall, the repair is work for a licensed plumber.
Arranging a shower leak investigation
If your shower seems to be wetting the room next door, find the cause before anyone pays to retile. If you need a shower leak investigation on the Gold Coast, get in touch with HydroIQ to arrange one.
Common questions
General information for South East Queensland home owners, not advice about your building or a legal matter. Standards and time limits change; check the current edition or rule before relying on a figure here.