Shower waterproofing: what is behind the tiles?
Tiles and grout alone do not guarantee a waterproof shower. The protection behind them matters just as much as the finish you see.
A suitable waterproofing system helps keep shower water away from the walls and floor underneath. Planning it before tiling means considering the whole shower, including corners, pipes and the drain or shower tray.
What makes a shower waterproof?
Waterproofing is a separate part of the construction. Water-resistant grout can help, but it does not replace that protection. Neither does a tile sealer or a visible bead of silicone.
There are three common approaches. The right choice depends on the surface underneath, the shower design and how the different materials connect.
Sheet membranes
These are waterproof sheets fitted before the tiles. Some have a fabric-like surface to help the adhesive grip, but ordinary fabric or mesh is not a waterproof membrane.
The joins and corners need to be sealed as part of the system.
Liquid membranes
These are brushed, rolled or spread onto a prepared surface. They form a waterproof layer once they have dried or cured.
The correct thickness and drying time matter, along with any sealing bands or reinforcement required at junctions. A surface that looks covered is not necessarily protected properly.
Waterproof boards
Some boards provide both a surface for tiling and waterproof protection. Their joints, fixing points and connections still need the specified sealing treatment.
A board described as moisture-resistant is not necessarily waterproof. Its suitability for the shower must be checked.
The details matter
Whichever system is chosen, it must connect properly around:
- Corners and the junction between walls and floor.
- Openings for pipes and fittings.
- Recessed shelves, also called niches.
- The drain or shower tray.
A tiled shower floor also needs suitable falls towards the drain. A niche needs detailing that allows water to drain out. These features should be planned together with the waterproofing, rather than added afterwards.
What if I have a ready-made shower tray?
The tray collects water, but the adjoining walls and the tray-to-wall connection still need appropriate protection. The visible sealant joint needs maintenance and should not be assumed to provide all the protection the installation needs.
Three questions to ask your installer
- Which waterproofing system will you use, and where?
- How will you seal the corners, pipes and drain or tray connection?
- What checks will you carry out before tiling?
Clear answers help you understand what is included in the work. Photographs taken before tiling can also provide a useful record of details that will later be hidden.
Planning your shower with Morfohouse
A beautiful shower starts with decisions about what you see and what sits behind it. Discuss your layout, tile choices and waterproofing with Morfohouse as part of your bathroom design and renovation.
Contact Morfohouse to discuss your bathroom.
Technical references: UNE 138002 and the selected waterproofing manufacturers’ installation guidance. Prepared October 2026. Product-specific requirements depend on the installation.