Water from my bathroom is leaking into the flat below — how is it actually fixed?

Question

I've had a knock from the neighbour below — there's a damp patch spreading on their ceiling, and it's directly under my guest bathroom, which lines up with the shower.

I got a plumber in first. He pressure-checked and says the supply and drain pipes are fine, no pipe leak. His view is that water is getting through the shower floor/wall area itself and down into the slab.

So now I'm confused about the fix. One handyman said he'll just re-grout and re-silicone the shower and that'll sort it. Another said the whole shower needs stripping and re-waterproofing, which sounds like a big, expensive job.

Which is right? What's actually leaking if it's not the pipes, and is re-grouting ever enough, or am I looking at ripping the bathroom out? Trying to do this once, properly, because the neighbour is (understandably) not happy.

Tarek H. · Accepted Answer

The handyman offering to just re-grout is the reason these leaks come back. Here's the thing almost everyone gets wrong: grout, silicone and tiles are the finish, not the waterproofing. Water passes through grout lines — it's *meant* to. What's supposed to stop it reaching the slab (and your neighbour) is a waterproofing membrane hidden under the tiles and screed. If water is reaching the flat below and the pipes are clear, that membrane has either failed, was applied badly, or was never there — very common in older fit-outs.

Re-grouting seals the very top surface for a few weeks, then water finds the grout lines again and you're back to a wet ceiling downstairs. It doesn't touch the actual problem.

The proper fix: strip the shower area back to the substrate, apply a fresh waterproofing membrane — carried up the walls as an upstand, with the corners and the drain/pipe penetrations properly detailed — check the screed falls run to the drain, flood-test it, then re-tile. Yes it's more than a re-grout, but it's the only version that stops the leak for good. You often only need to redo the wet zone (shower + splash area), not the entire bathroom, which keeps it sensible. Get a team that does bathroom re-waterproofing and re-tiling rather than a general handyman — the membrane detailing is where these jobs are won or lost.

Act quickly, though: the longer it soaks the slab, the more of the ceiling below (and its finishes) you'll end up responsible for.

Yusuf T. · Answer

Good that you ruled out the pipes first — that's the right order. One thing to double-check before you commit to stripping the shower: the floor drain (puddle flange) connection. Where the drain body meets the waterproofing is a classic failure point — if that seal is gone, water runs straight past into the slab even with a decent membrane elsewhere. A good waterproofing crew will inspect that joint as part of the job. And rule out the AC drain in the ceiling void too, just so you're certain it's the shower and not two problems at once.

Jason S. · Answer

Practical/neighbour side: put it in writing to your building management now, and keep dated photos of their ceiling and your repair. Water-damage disputes between units get messy fast, and being the one who documented it and fixed it properly (membrane, not a grout smear) puts you in a much better position. Fixing it cheap and having it recur will cost you more in goodwill than the job itself.

Water from my bathroom is leaking into the flat below — how is it actually fixed?

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