A wet room is a bathroom in which the floor, and the walls in the shower zone, are fully waterproofed so that water can be allowed to reach them; the shower has no tray and drains through a floor gully. More broadly, the term is used on drawings and in specifications for any room containing sanitary fittings where surfaces regularly get wet: bathroom, shower room and WC.
Why it is treated separately
A wet room differs from every other room in a dwelling by four things at once: standing and splashing water, high humidity, a lot of pipework in a small area, and finishes that are not vapour open. That calls for its own detailing.
- Tanking — a continuous waterproofing layer beneath the tiling, carried over corners and junctions with sealing tapes and collars. Tiles and grout are not themselves waterproof
- Falls — the shower area is laid to fall towards the gully; roughly 1 to 2 cm per metre is usual, enough for water to run away without the floor feeling sloped
- Ventilation — mechanical extract is essential, and it only works if replacement air can get in through an undercut door or a grille
- Pipework — water pipes in an external wall or an unheated duct can freeze; keep them on the warm side of the insulation
Prefabricated units
In housing, hotel and healthcare projects the wet room is also supplied as a complete prefabricated pod: a factory-finished bathroom including tiling, fittings and services, craned into the frame. Advantages are consistent waterproofing quality and a shorter programme; disadvantages are weight, crane access and the limited scope for later changes.
Points to watch
- Carry the waterproofing at least 200 mm up the wall, and full height within the shower zone
- Avoid timber or gypsum-based backing boards in the splash zone; use cement-based tile backer board
- Form the floor-to-wall junction as a flexible sealed joint; a rigid joint cracks as the structure moves
- A level-access shower needs a lowered or recessed floor construction — plan it into the structure, not into the finishes
- Check that the shower and WC discharge into an adequately vented drainage stack, or the traps siphon out and the room smells
Related terms
- Bathroom
- Floor gully
- Tanking
- Mechanical ventilation
- Tiling
- Sanitaryware
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.