(If you haven’t already read the first section of How to Install Tile in Showers, we recommend that you do so.)
After the hot mopped shower pan has cooled down, we filled the shower pan with water up to just below dam height. A measurement was taken (9 5/8″) to establish a known point and the pan was left overnight for a recommended water test.
The next day, we checked the area below the new pan for leaks; based on checking the measurement we determined that no water was missing.
The original shower pan installer used a material other that roofing felt that appeared to be more like asphalt impregnated paper. Also the membrane did not extend above dam height by the required 3″ minimum. Additionally the membrane was stapled through the top of the dam. These factors all contributed to the shower pan failure.
The next step after draining the pan is to protect the investment with the use of craft type paper or some barrier that will help prevent the penetration of the pan with any tool or object.
Next install a suitable solid backing unless a scratch coat is desired. The solid backing here consists of ½” water resistant gypsum board (“green-board”) that is fastened to the studs, appropriately joint taped, and which has one coat of drywall compound on the joints and screw-heads.
We applied 15 pound roofing felt over the drywall from the top of the dam to the ceiling complete with 4″ overlapping joints.
Allow the ceiling paper to overlap the wall paper if the ceiling is to be tiled. Make sure the felt overlaps the hot mop at least to dam height.
The 2.5 pound metal lath is installed next with a minimum 2″ overlap at seams, is cut at all 90° corners, and is terminated at the intended point of floor mortar height.
Mix wall mortar in the appropriate ratio(s) and begin the mortar installation by “keying” in the mortar fully embedding the wire reinforcing.