By the time a ceiling below is staining, water has usually been tracking through a wall or floor build-up for months.
The three routes water takes
Movement at the bath-to-wall joint, where an acrylic bath deflects as it fills and empties and tears a thin bead of silicone. Grout and tile backgrounds that were never designed to be waterproof, so water passing the grout meets plasterboard. And the shower tray or waste connection itself, which leaks only while the shower runs.
Isolating which one you have is a matter of testing each in turn rather than resealing everything and hoping.
What proper waterproofing looks like
Tiles and grout are a finish, not a waterproof layer. In a shower area the waterproofing is the tanking behind them: a bonded membrane or a liquid system carried over the floor junction, into the corners and over any board joints.
Backing boards matter too. Cement or foam tile backer boards in wet zones do not soften the way standard plasterboard does when water finds them.
Getting details right at the edges
Support baths so they cannot flex, use a proper sealing profile or a wider, well-tooled joint, and bed the bath before tiling down onto it rather than the other way round.
For a wet room, the falls, the drain position and the linear or point outlet all need to be planned before anything is laid — retrofitting a fall into a finished floor is not possible without lifting it.
Common questions
Why does my bath sealant keep failing?
Usually flex. If the bath moves as it fills, a thin silicone bead cannot bridge the movement. Supporting the bath and using an appropriate joint detail solves it.
Are tiles and grout waterproof?
No. Grout is porous and tiles rely on the layer behind them. In a shower area the tanking membrane is what keeps water out.
Can you fix a leak without stripping the bathroom?
Sometimes, if the source is a waste connection or a single joint. Where water has passed a tiled background, the tiling in that zone usually has to come off.
How long does a bathroom refit take?
A typical full refit runs a few weeks depending on the extent of first-fix plumbing and electrics and whether the layout changes.