Yes. A wet room needs a continuous waterproofing system beneath the visible floor and wall finish. This is commonly called tanking. Tiles, grout and decorative wall panels may resist water, but they should not be treated as the only protection against moisture reaching the building fabric.
What does wet-room tanking do?
Tanking forms a sealed layer across the shower floor and other areas specified by the system manufacturer. It is detailed around the drain, corners, wall-to-floor junctions and pipe penetrations. If water passes through a joint in the finished surface, the tanking prevents it reaching plasterboard, timber, insulation or the room below.
A typical system may use a pre-formed shower former, waterproof membrane or coating, sealing tapes, internal corners and compatible adhesives. The important word is system: the components must work together and be installed to the manufacturer’s instructions.
Why are tiles and grout not enough?
Grout lines, movement joints and sealant can deteriorate. Timber floors move slightly under normal use, and small gaps can develop around pipes or the waste. A properly prepared waterproof layer gives protection behind the finish rather than relying on the surface remaining perfect forever.
This matters especially upstairs, where a slow leak may damage a ceiling before it becomes visible in the bathroom.
Which areas need waterproofing?
The exact extent depends on the room, shower position and selected system. In a fully open wet room, the complete floor is commonly waterproofed with the membrane turned up at walls. Walls within the shower zone also need suitable protection. Doorways, service penetrations and changes of material require careful detailing.
Where a low-profile tray is used, the waterproofing arrangement may be more localised, but surrounding walls and joints still need a water-resistant specification.
What preparation is needed before tanking?
- The base must be sound, clean and suitable for the chosen system.
- Movement in boards or floors must be controlled.
- The shower fall and drain position must be formed before the final finish.
- Corners and penetrations must be accessible for tapes and seals.
- Drying and curing times must be respected before covering the membrane.
Tanking cannot correct a badly supported floor or an incorrectly installed drain. Those issues must be resolved first.
How can a homeowner check the specification?
Ask the installer to state the tanking system in the quotation and explain how it connects to the shower waste. Useful questions include:
- Is the floor former compatible with the membrane?
- How far will the waterproofing extend?
- How will corners and pipe entries be sealed?
- What is the required curing time?
- What access will remain for drainage maintenance?
Photographs taken before the surface finish is fitted can provide a useful record of the hidden work.
Does Building Regulations approval apply?
The waterproof finish itself is only one part of the project. Structural, drainage, ventilation and electrical changes may need building-control approval or competent-person certification. The Planning Portal guide to accessible adaptations explains that approval is likely where those elements are affected.
Frequently asked questions
Can wall panels replace tanking?
Panels can provide an excellent hygienic and low-maintenance finish, but the full installation must still manage water at joints, edges and penetrations. Follow the panel and wet-room system specifications rather than assuming the face of the panel solves every detail.
Can you tank over old tiles?
Sometimes a manufacturer permits work over a sound existing surface, but hidden condition, adhesion and finished floor levels must be assessed. Removing the old finish is often the only way to inspect and correct the substrate.
Is tanking needed beneath safety flooring?
Safety flooring may be welded and detailed to form a water-resistant surface, but the construction must be designed as a complete wet-area system. The correct approach depends on the flooring product, drain and room layout.
EverSafe’s survey and quotation set out the wall, floor, drainage and waterproofing approach before installation. Book a free home visit to discuss the room.
