How to Plan a Wet Room Installation in 2026 (UK)

Planning a wet room step by step

A wet room is a fully waterproofed (“tanked”) bathroom where the shower area drains directly through the floor, with no tray or enclosure kerb. The planning order below matters — each stage depends on the one before it.

1. Assess the floor structure and drainage feasibility

Concrete floors are the easiest to work with — the drain and falls can be formed directly. Suspended timber floors need a purpose-made sloping shower former (deck) let into the joists, plus reinforcement and often notching that a structural check must approve. Confirm the waste can reach a soil stack at the required fall before anything else — this is the single most common reason a wet room won’t work in a given room.

2. Choose and install a full tanking (waterproofing) system

The waterproof membrane is what makes it a wet room, not the tiles. Use a complete tanking kit — liquid membrane or matting with reinforced tape at every joint, corner and pipe penetration, taken up the walls to at least 1.8m in the shower zone. Skimping here is the number-one cause of failure.

3. Set the drainage falls to the gully

Water has to run to the drain by gravity. Aim for a fall of roughly 1:40 to 1:80 across the shower area to a linear channel or point drain. Pre-formed sloping shower decks build the correct fall in automatically; screeded floors need the fall trowelled in by an experienced fitter.

4. Plan electrics, ventilation and heating to building regs

Electrical work in a bathroom is notifiable under Part P and must respect the IP-rated zones around the shower. Adequate extract ventilation is required under Part F to control moisture — see our guide to bathroom extractor fan installation. Underfloor heating is popular in wet rooms because it helps the floor dry quickly. Use slip-resistant tiles (R10/R11) for safety.

5. Hire a qualified wet-room fitter and compare three quotes

Wet rooms are unforgiving of poor workmanship. Choose a fitter with specific wet-room and tanking experience, ask to see previous jobs, and compare three quotes on the same written scope including the tanking system and building-regs sign-off. Our checklist for hiring a trusted bathroom fitter covers the questions to ask.

Common wet room mistakes and how to avoid them

Most wet room failures trace back to a handful of avoidable errors made before a single tile goes down. Knowing them helps you brief your fitter and check the work as it progresses.

Skimping on the tanking membrane

The single biggest cause of leaks is an incomplete or poorly detailed waterproof membrane. Best practice under BS 5385-1 is to tank the whole floor and take the membrane at least 150mm up every wall — and to full height in the shower zone — with reinforced tape bonded at every internal corner, joint and pipe penetration. Budget £500–£1,500 for the tanking materials alone; it is the last place to cut costs.

Tiling onto the wrong background

Never tile directly onto standard plasterboard in a wet zone. Use a tile backer board — cement board or waterproof foam board (for example Wedi or Jackoboard) — or moisture-resistant board with a full membrane over it, so the substrate stays protected if a grout line ever fails.

Getting the fall or drain position wrong

A shower area that is too flat leaves standing water; a drain placed against the fall direction never fully clears. Set a fall of at least 1:80 (ideally around 1:60) to a correctly positioned linear or point gully, and dry-test the drainage with a bucket of water before any tiling starts.

Forgetting ventilation and regs sign-off

Trapped moisture rots timber and blackens grout. Mechanical extract ventilation is a legal requirement under the Building Regulations — see the government’s Approved Document F (ventilation) — and the electrics must be certified under Part P. Confirm in writing who is providing the building-regs sign-off before work starts.

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