How to Install a Shower Pan Liner

Liner installation is the singular most important step in preventing long-term water damage in a custom-built tiled shower. If your base leaks, the subfloor rots, and the entire room eventually fails from the ground up. Done well, your liner forms a seamless, watertight bathtub-like reservoir that directs any water that manages to bypass your tile directly into the drain assembly. Take your time with the corners and ensure you don't use any fasteners below the water line of your curb. A shower pan that holds water for a test period is a job well done. We are looking for a perfectly graded floor that slopes toward the drain and a liner that remains uncompromised by stray nails or careless stapling.

1. Slope the Floor First. Apply a thick mortar bed over the subfloor so it slopes at least a quarter-inch per foot toward the drain flange. Allow this to cure until it is firm enough to walk on without deforming.
2. Unroll and Position Liner. Lay the sheet of CPE or PVC liner over the floor and up the walls. Ensure you have at least 10 inches of excess material running up the wall studs and enough to fold over the curb.
3. Fold, Don't Cut Corners. Fold the liner into the corners rather than cutting it. Use extra care to avoid stretching the material thin, as tight folds are more reliable than patches.
4. Staple High, Never Low. Staple the top edge of the liner to the wall studs. Never place a staple or screw less than 10 inches above the finished floor level to prevent water leaks.
5. Seal and Bolt Drain. Locate the drain hole by pressing the liner over the flange. Carefully cut a hole slightly smaller than the flange opening, then bolt the top section of the drain assembly to the base.
6. Let Water Do the Work. Plug the drain with a test plug and fill the pan with water up to just below the curb. Let it sit for 24 hours and monitor the area below for any signs of moisture.