Shower Membranes vs Shower Liners
Your shower is not complete without a liner or a shower membrane. If you have to install masonry tile, you should always have a membrane because the material is not waterproof. Water will seep into the floor grout and shower base.
Advantage of the Shower Membrane
The shower membrane is usually made from vinyl. It is installed on the mortar base. There have been various liners that have been used in the past that were made from copper, lead, steel, and iron. Some people even use tar. None of these materials are as effective as shower membrane, which is considered to be the best solution for water seepage in a shower.
The Problem With Shower Liner
Shower liner sheets are usually made from either Chlorinated Polyethylene (CPE) or Polyvinyl Chloride. You get more flexibility from CPE, and it stays soft longer. The material is harder to find ,and it can be comparatively expensive. That is why PVC shower liners are more common. PVC difficult to bend and fold, making it more difficult to conform to your floor construction.