A bathroom does not announce that its waterproofing has gone. There is no drip, no puddle and nothing obviously broken. What happens instead is that water starts going somewhere it was never meant to go, slowly, every single day, and the first visible sign turns up in a room that is not the bathroom.
The housing around here is mostly 1960s to 1980s, which means a great many original wet areas are now 55 to 75 years old. Waterproofing is a consumable. It was never meant to last that long, and the question in most of these houses is not whether it will need doing but whether it already has.
Waterproofing fails invisibly, so you watch for the secondary signs instead: loose or hollow tiles, dark grout that never dries, swollen skirting or a soft patch in the next room, a musty smell that returns, and paint lifting on the far side of the shower wall. Any two of those together is worth investigating properly.
- Tap the tiles in the shower and listen for hollow ones
- Check the skirting and floor in the room backing onto the shower
- Look at the ceiling below if there is one
- Watch whether grout in one area stays dark for days
- Get it looked at before the next renovation, not during
On this page
1. Waterproofing is a consumable, not a permanent feature
People treat a bathroom as though it either works or is broken. In practice the membrane behind the tiles is a layer with a working life, like a roof cover or a hot water anode, and it wears out on its own schedule regardless of how well the room has been looked after.
That matters here more than it does in newer suburbs. The dominant housing across this area went up between the 1950s and the 1980s: three-bedroom brick veneer and fibrous-cement homes on blocks of six to nine hundred square metres. A lot of those wet areas are still the original ones, now well past half a century old.
Current work is done to the Australian Standard for waterproofing wet areas, AS 3740. An original 1965 bathroom was not built to that standard, because it did not exist yet. That is not a criticism of the builder. It is simply the reason a sixty-year-old wet area should be treated as a question rather than an assumption.
A bathroom that has been kept beautifully still has a membrane of the same age as the house. Appearance tells you about the tiles, not about what is behind them.
2. The signs, roughly in the order they appear
- Grout that stays dark. One patch that is still darker than the rest a day or two after anybody showered means it is holding water rather than shedding it.
- Hollow-sounding tiles. Tap along the shower wall and floor with a knuckle. A change from solid to hollow means the bed behind has lost its bond, and water is usually why.
- Grout or silicone that keeps failing in the same spot. Redoing it every year is not maintenance, it is a symptom.
- A musty smell that comes back. Particularly one you notice on returning to the house rather than while living in it.
- Swollen skirting or soft floor in the next room. This is the one that usually gets somebody to ring, and by then water has been moving for a while.
- Paint lifting or a stain on the far side of the shower wall. Same situation, different finish.
One of these on its own can have an innocent explanation. Two of them in the same part of the house is a pattern, and patterns are worth acting on while they are still cheap.
3. Where the water actually goes
This is the part that makes ageing waterproofing expensive rather than annoying. Water getting past the membrane does not sit still. It follows the fall of the floor, or the line of a joist, or the back of a wall sheet, and it emerges wherever that path happens to end.
In a brick veneer house that is frequently the timber frame and the bottom plate behind the wall. In a house on a suspended timber floor it is the joists and bearers underneath, which nobody looks at. In either case the visible damage appears somewhere other than the room causing it, which is exactly why people spend a year repainting a hallway.
The other consequence is that the longer it runs, the less of the eventual bill is plumbing. Replacing a membrane is a defined job. Replacing framing timber that has been wet for three years is a different conversation entirely.
In housing of this age the framing, the roof cover and the wet areas all reached the end of their service lives around the same time, because they all started at the same time.
4. What you can check yourself in ten minutes
- Tap along the shower walls and floor with a knuckle, listening for a change from solid to hollow. Note where it changes.
- Run a hand along the skirting in the room that backs onto the shower, low down. Soft, swollen or lifting paint is the sign.
- If there is a room or garage below, look at the ceiling directly under the wet area.
- Shower normally, then look at the grout the next morning. Anything still visibly darker is holding water.
- Look at where the silicone meets the floor. Continuous failure in one corner is telling you where the movement is.
- Check the floor waste actually drains freely. Water sitting on the floor is water looking for a way through.
None of that requires tools or a licence. What it does is turn a suspicion into a location, which is the difference between a targeted look and an exploratory one.
5. Patching, repairing or doing the room
Where the membrane is intact and the problem is a failed seal, a leaking waste or a tap body weeping behind the wall, that is a repair. It is worth establishing that first, because it is far cheaper and it is genuinely what a lot of these turn out to be.
Where the membrane itself has gone, patching over the top of it does not restore it. Re-grouting a floor whose waterproofing has failed buys a season. It is an entirely reasonable thing to do if you have a plan and a date for the real work; it is a poor thing to do instead of one.
The practical advice is to find out which situation you are in before you commit to either. That single answer decides whether this is a few hundred dollars or a renovation, and it is worth knowing before somebody starts removing tiles.
Not sure whether it is a seal or the membrane?
We can test the wet area and tell you which of the two you are dealing with before anything comes off.
6. If a renovation is coming anyway
Get the plumbing looked at before the design is settled rather than after the tiles are chosen. In housing of this age the pipework behind the wall is frequently as old as the membrane, and finding that out mid-job is how a bathroom renovation acquires an extra fortnight.
It also matters where the fixtures are going. Moving a shower or a toilet is a drainage question first and a design question second, and the answer is much cheaper to obtain while it is still a drawing.
One more thing specific to housing of this era: in a fibro or early brick veneer house, assume there is bonded asbestos in the wet area linings until somebody qualified has established otherwise. That is not a scare, it is the order of operations, and it is covered properly in our guide on renovating a wet area in this housing.
- Waterproofing is a consumable with a service life, not a permanent part of the house.
- Most housing here is 55 to 75 years old, so original wet areas are at or past that life.
- It fails invisibly. You watch for hollow tiles, dark grout, soft skirting and musty air.
- Water leaves the bathroom along framing and joists, so the damage shows up in another room.
- A failed seal is a repair. A failed membrane is a renovation. Find out which before starting.
- In fibro and early brick veneer, assume bonded asbestos in the linings until it is checked.
Ageing bathroom waterproofing FAQs
How long does bathroom waterproofing last?
It depends on what was used, how it was installed and how hard the room is worked, so we will not put a number on a bathroom we have not seen. What is fair to say is that an original wet area in a house built in the 1960s or 1970s has had a very long run and should be treated as a question rather than assumed sound.
Can waterproofing be repaired without removing the tiles?
Sometimes the problem is not the membrane at all, and then yes. Where the membrane itself has failed, restoring it means getting to it. Coatings applied over the top of failed waterproofing manage the symptom for a while rather than fixing it.
Is a hollow-sounding tile always a waterproofing problem?
No. Tiles can debond for other reasons, including how they were laid. It is a sign worth noting rather than a diagnosis, which is why it is more useful alongside the other signs than on its own.
The damage is in the hallway, not the bathroom. Why?
Because water follows the fall of a floor or the line of a frame before it emerges. The point where you can see it is usually downhill of the point where it got in, which is why repainting the hallway never solves anything.
Should I re-grout it and see?
As a holding measure with a plan behind it, that is reasonable. As a solution, it is not. Grout is not the waterproofing layer, and treating it as though it were is the single most common reason a small problem becomes a framing problem.
Does an old bathroom have to be brought up to current standards?
Existing work is not retrospectively required to meet a standard written after it was built. New work is. So the moment the room is renovated, the waterproofing goes in to the current Australian Standard, which is one of the genuine benefits of doing it properly.