Key takeaways
- Tile and grout resist water but do not stop it. A membrane behind them does.
- Corners, seams, niches and pipe openings are where leaks start.
- A flood test before tiling is a simple way to confirm the pan holds water.
- Follow the maker's instructions for each system and do not mix and match parts.
Why tile is not enough
Grout is porous and cracks over time, and tile is only a surface. Water passes through, reaches the layer behind and, without a membrane, soaks into the wall and floor. The result can be rot, mold and damage to rooms below.
Waterproofing is therefore a layer in its own right, not a coat of paint or a sealer.
Types of membranes
Sheet membranes are bonded in place with seam tape and corner pieces. Liquid-applied membranes are rolled or brushed on in coats and often include reinforcing fabric at corners. Foam boards with sealed seams offer both insulation and a waterproof surface. Each has strengths, and each works only when installed as the maker requires.
The right choice depends on the shower design, the substrate and the tile.
Details that decide success
Inside corners, curb edges, the drain flange, valve and showerhead penetrations and niches are all points of failure. Each must be sealed with the proper corner pieces, tape or sealant. Slope matters too, because pooling water stresses the system.
A rushed detail can hide a leak for years.
Testing and documentation
After the membrane cures, plug the drain and fill the pan with water. Mark the level and wait. If the level holds, the pan is sound. Photos of the membrane before tile are useful records for you.
Ask any contractor how they test and what they will show you.
Official sites to explore
Brand names and logos belong to their owners. These links open the official websites in a new tab, and we are not affiliated with them.
- Schluter SystemsMaker of waterproofing membranes, drains and shower systems.
- LATICRETEMaker of waterproofing and tile setting materials.
- Custom Building ProductsMaker of tile installation products and waterproofing.
- Tile Council of North AmericaIndustry resources on tile installation standards.
- International Code CouncilPublisher of model building codes.
Quick answers
Is cement board waterproof?
It resists water damage but is not a waterproof layer by itself.
Can I waterproof over old tile?
Generally not. If a shower leaks, the tile needs to come out so the system can be rebuilt.
How long does a membrane last?
A properly installed membrane can last as long as the shower. Failures are usually from poor details or damage.
