Four legitimate approaches
| System | How it works | Notes |
|---|---|---|
| Bonded sheet membrane | Sheet bonded with thinset, seams banded | Tile can follow quickly; the most common choice |
| Liquid-applied membrane | Coats rolled on with reinforcing fabric | Good for complex geometry; must cure fully |
| Foam board system | Waterproof panels acting as substrate | Strong fit for curbless and prefabricated trays |
| Mortar bed with pan liner | Sheet liner under a sloped bed, weep drain | Traditional; mostly seen in repairs and matching work |
Where failures start
- Inside corners taped rather than banded
- Drain flange and membrane from different manufacturers
- Wall membrane terminated behind the pan instead of lapped over it
- Unsealed valve and shower-arm penetrations
- Tile set over liquid membrane that had not cured
- Movement joints omitted at changes of plane
A shower can leak for years with no symptom inside the shower. Cupped flooring or a stain on the far side of a wall usually means the framing has been wet for a long time.
The flood test
- 1Plug the drain and fill the shower floor with water
- 2Mark the water level and leave it standing for a sustained hold
- 3Check the mark, and check the ceiling below where the shower is over finished space
- 4Photograph the waterproofing before it is covered, and keep the photographs
- 5Only then set tile