The Shower Pan Liner Membrane Is The Key
Shower pan liner membranes in the past were copper, galvanized steel, iron, lead and even tar. In time, all tend to fail for one reason or another. Currently most shower pan liners are a plastic sheet which seems like it will last a very long time. Time will tell.
The actual shower liner is either a chlorinated polyethylene (CPE) or polyvinyl chloride (PVC) sheet. Either works. The CPE is more flexible and seems to stiffen slower. But, it's harder to find and more expensive. That means most installers use PVC liners.
The PVC liner is installed between two mortar layers. It runs up the wall at least 2 inches above the height of the finished curb. It goes all the way over the curb too.
Key points...
The sheet membrane is sealed to the top of the drain base. That means water is routed from the liner sheet tot he lower drain holes in the special shower drain. That's how water that seeps through the shower floor gets in the drain and not in the subfloor.
The liner is folded in the corners so there are no cuts. But to get the liner over the curb, there must be some cuts. One way to seal at the cuts is to use special dam pieces which are glued in place at every corner to perfectly seal at joints.
Also no fasteners should be put in the liner except near the very top of the liner and on the outside of the curb.
The shower liner is always installed over a sloped base to insure that water never pools in the shower floor. Water that makes it to the liner runs right toward the drain. Don't even think about installing a shower pan liner over a flat floor. That's a guaranteed problem ceramic tile shower.
Next is getting the shower pan membrane up the wall like it should be...
Click Here for the next article... about going up the wall.