Walk-In Shower Leaking Through Floor
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →If water is reaching floor joists or concrete below the shower, this can cause significant structural damage over time. Act quickly — delaying increases repair costs substantially.
A walk-in or wet room shower leaking through the floor is a serious issue. The cause is almost always a failure in the waterproof membrane (tanking) applied under the tiles, or at the drain connection. Tracing the exact source requires methodical testing — sometimes a professional leak detection company can help.
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Most likely cause & what to check
First confirm the shower is actually the source. Block the shower drain temporarily (a drain plug) and fill the shower floor with 5–10cm of water. Watch for 30 minutes. If the ceiling below becomes wet or damp, the floor waterproofing has failed. If it stays dry, the leak is coming from the walls or drain connection rather than the floor.
Check the drain connection — the shower waste fitting where it goes through the floor is a common failure point. The rubber seal around the drain body can perish, especially in wet rooms. A plumber can sometimes access and replace the drain seal from below without lifting tiles.
Inspect the grout and silicone joints at floor level, especially at the junction between the floor tiles and wall tiles. If grout is cracked or missing, water tracks into the substrate. Re-grout and re-silicone these joints as a first step — this fixes many wet room leaks.
If the waterproof membrane has failed under the tiles, a full retile is needed. The tiles must be removed, the existing tanking assessed and repaired or replaced, and the floor retanked before relaying tiles. This is a significant job (£800–2,500 depending on area).
For a ceiling repair alongside, wait until the shower floor is fully fixed and dried out (can take 4–8 weeks in a concrete floor) before plastering the ceiling — plastering over damp is wasted effort.
Get 2–3 quotes from tiling contractors experienced in wet room waterproofing — this is a specialist skill. Ask specifically whether they will use a sheet tanking membrane (e.g. Schlüter KERDI) or liquid applied tanking, and which they recommend for your floor construction.
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