Plumb a wet room.

For homeowners, this transition requires precision plumbing and specialist "tanking" (waterproofing) to protect the property's structural integrity. While it adds significant value to your home, a wet room is a complex installation that demands a high level of technical skill to ensure the water stays exactly where it should.

What Does the Work Involve?

• Site Survey: Assessing floor joist depth and drainage height to ensure a level-access finish is physically possible.
• Subfloor Preparation: Removing existing flooring and reinforcing joists to support the weight of a new screed or a pre-formed "former" tray.
• Drainage Installation: Rerouting waste pipes and installing a high-flow gully or linear drain with a built-in trap.
• Tanking (Waterproofing): Applying a multi-layer waterproof membrane to the floor and "upstanding" the walls to create a watertight seal.
• Creating Falls: Ensuring the floor slopes accurately (usually a 1.5% to 2% gradient) toward the drain to prevent pooling.
• Plumbing & Finishing: Installing thermostatic valves, shower heads, and tiling with specialist waterproof adhesive and epoxy grout.
• Commissioning: Testing the flow rate and water-tightness before the final handover.

Typical Costs

The cost of a wet room varies significantly based on the size of the room and whether you are converting an existing bathroom or starting from scratch in a new extension. Structural repairs to joists or the need for a pumped waste system can also increase the final bill.

Pro Tip: Never skimp on the tanking system. The cost of fixing a leak in a wet room often exceeds the original installation price, as tiles must be ripped up to access the membrane.

How Long Does It Take?

• Initial Survey & Strip-out: 1–2 days. This includes removing the old suite and exposing the floor structure.
• Structural & Plumbing Prep: 2–3 days. Rerouting pipes and installing the floor former or screed falls.
• Tanking & Curing: 1–2 days. The membrane must be applied and allowed to dry completely before tiling begins.
• Tiling & Grouting: 2–4 days. Wet rooms require precise tile cuts to maintain the floor's gradient.
• Final Fit & Testing: 1 day. Installing the shower screen, valve, and conducting a final leak test.

DIY or Professional?

Wet room installation is not recommended as a DIY project. While a confident DIYer can fit a standard bathroom, the consequences of a poorly installed wet room are severe, potentially leading to rotted joists and collapsed ceilings.

Professional plumbers or wet room specialists have the tools to ensure correct floor falls and the experience to apply tanking membranes without pinhole gaps. Furthermore, any electrical work (such as underfloor heating or extractor fans) must be completed by a Part P registered electrician to comply with UK Building Regulations.

Choosing the Right Tradesperson

• Check Specialisms: Look for a plumber who specifically mentions wet room installation or "tanking" experience, not just general plumbing.
• Verify Insurance: Ensure they hold valid Public Liability Insurance (minimum £2 million).
• Review Portfolio: Ask to see photos of previous wet room projects, specifically "in-progress" shots of the waterproofing stage.
• Red Flags: Be wary of anyone who suggests tanking isn't necessary or who proposes using standard "moisture-resistant" plasterboard without a secondary membrane.

Questions to ask:

• "What specific tanking system do you use, and does it come with a manufacturer's warranty?"
• "How will you ensure the floor has the correct fall to prevent water pooling?"
• "Are you happy to provide a written, itemised quote including waste disposal?"

UK Regulations

• Part P (Electrical Safety): All electrical work in "special locations" like bathrooms must be certified and notified to Local Authority Building Control.
• Part M (Access): If the wet room is being installed to meet accessibility needs, it may need to comply with specific dimensions for wheelchair turnaround.
• Building Regulations: You must ensure the floor structure can handle the additional weight of a screed and that ventilation (extractor fans) meets current airflow standards (15 litres per second).
• Paperwork: Expect a completion certificate if structural or significant electrical work was carried out.

Common Problems

• Poor Drainage: If the floor fall is too shallow, water will pool in corners, leading to stagnant smells and slippery surfaces.
• Leaking Thresholds: Water escaping under the bathroom door usually indicates a failure in the tanking "upstand" or a lack of a slight transition slope at the door.
• Mould Growth: Wet rooms generate significant steam; without a high-powered, humidistat-controlled extractor fan, mould will quickly form in grout lines.
• Cracked Tiles: Usually caused by floor movement. Using a decoupling membrane and flexible adhesive is essential to prevent this.

Frequently Asked Questions