A shower screen leaking at the base is almost always the door, the track or the seal around the glass, not the waterproofing membrane behind the tiles. The screen and the membrane are two separate barriers doing two different jobs, and it's worth checking the screen first before assuming the more expensive one has failed.
Two barriers, not one
The membrane behind the tiles, installed to AS 3740, is what stops water getting into the floor and wall structure if it gets past the tiles at all. The screen sits upstream of that. Its job is to keep the bulk of the water, the spray and the runoff, inside the enclosure in the first place, so the membrane only ever has to deal with what gets past a grout joint rather than a running stream. A screen leaking at the base means that first job isn't happening, which is a screen, track or seal problem well before it's anything to do with the membrane.
Start with the door itself
Sliding and hinged shower doors both rely on a strip along the bottom edge, a sweep or a wiper, to direct water back down into the shower rather than let it run straight off the edge of the glass. That strip is rubber or PVC and it perishes, splits and goes stiff well before the glass or the frame show any wear. A door that used to seal and now doesn't is usually this strip rather than anything structural, and it unclips and replaces without touching the rest of the screen. Hinged doors also rely on hanging square in the frame, so a door that's dropped slightly on its hinge will open a gap at the bottom corner even with a good seal fitted.
The track and the weep holes
A sliding door runs in a track with small weep or drain holes at its lowest point, there to let water that gets into the track drain back into the shower rather than build up and run out over the front lip. Soap scum and hair block those holes over time, and once they're blocked the track fills like a gutter and overflows at the first low spot, which usually shows up as water at one front corner rather than evenly along the whole base. Clearing the track out is a five-minute job and it's the first thing worth checking on a sliding door that's started leaking at one particular spot rather than generally.
The perimeter seal
Where the screen's frame or track meets the tiled hob and the wall, the join is sealed with silicone, and that joint is a wear item the same way the internal corners of a tiled shower are. It moves with the glass and the frame, it's exposed to the same water every day, and a few years is a normal life for it. Cracked, gone grey, or lifting away from the glass on one edge are all signs it's due, and resealing it is cheap and quick compared with everything else on this list.
When it's the glass, not the seal
A chip or crack in the glass is a different category of problem and not one to patch over. Shower screens use toughened safety glass under AS 1288, and a small chip on the edge of a toughened panel can be enough to release the tension holding the whole sheet together, sometimes well after the original knock. A cracked or chipped panel gets replaced, not resealed, and it's a glazier's job rather than ours.
How do you tell if it's the waterproofing membrane?
The membrane has failed rather than the screen when water turns up somewhere the screen was never covering: skirting or paint lifting in the room on the other side of the shower wall, a ceiling stain in the room below, or tiles well away from the door sounding hollow when tapped. Water that only ever appears right at the base of the screen, and nowhere else, almost always points at the screen. The tap test and the room-next-door check settle it either way if you're not sure.
Most shower screen leaks are the seal on the door, a blocked track or the perimeter silicone, all worth checking before assuming the tiles or the membrane behind them have failed. That's maintenance work that sits with the bathroom tiling we do. A membrane repair means lifting the tiles first, and a job like that usually runs past the $5,000 threshold, which is where it becomes licensed work rather than something to patch. Send a couple of photos of where the water's coming out and which check above matches what you're seeing.
Shower screen questions
Why does water leak out from under my shower screen?
Usually a perished seal on the bottom of the door, a track that's lost its weep holes to soap scum and hair, or perimeter silicone that's cracked or lifted away from the glass. All three are cheap, quick fixes. The waterproofing membrane behind the tiles is a separate barrier and a much less common cause.
Do I need to replace the whole screen if the glass is chipped?
Yes. Shower screens use toughened safety glass under AS 1288, and a chip or crack on the edge of a toughened panel can release the tension holding the whole sheet together, sometimes well after the original knock. A chipped panel gets replaced, not resealed, and it's a glazier's job rather than a handyman one.
How do I know if it's the waterproofing membrane and not the screen?
Look outside the enclosure. Skirting or paint lifting in the next room, a stain on the ceiling below, or tiles well away from the screen sounding hollow when tapped all point at the membrane. Water that only ever shows up right at the base of the screen, and nowhere else, points at the screen.
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