Hence, an improperly specified or installed shower pan or pan liner can often become a source of serious and costly problems. Sometimes they can even create environmental concerns.
Perhaps it¿s inappropriate to place the blame entirely on the shower pan or liner, because most problems occur due to improper construction ¿ usually related either to materials or methods. ¿Improper construction¿ can describe various deficiencies including the use of non-water-resistant drywall, or water-resistant (WR) drywall that¿s been installed incorrectly or has an improper slope to the drain.
The requirement for the slope to drain is ¥ inch per foot. In many cases, one will find that the prior construction did not provide the proper slope. As a result, the installer will encounter a flat substrate that requires remedial attention to be made acceptable.
In certain instances, the tile contractor must create the required slope with mortar ¿ sometimes incorrectly with the membrane underneath. In the end, this solution will not work because moisture and dirt will collect on the membrane and not move to the drain which, in turn, will create an odor and bacteria problem.
Shower pans are available in various forms, shapes and materials. Among these are fiberglass, hot-mopped asphalts, copper, lead, and even liquid-applied or sheet membranes that are designed to replace the plan itself.
Membranes are becoming increasingly popular because the material itself is cost effective and allows for a quicker installation, which also results in reduced labor costs. Prefabricated shower receptors that are often installed in tract homes must be set in mortar to prevent movement or flexing.
When a flat substrate is encountered, a proper slope can be realized by using preformed (manufactured) sloping devices (fig. 1). These are relatively inexpensive and they eliminate the additional costs that would be incurred by hiring a carpenter to build a slope or paying an installer to build one out of mortar.
A perfectly good slope membrane installation can go wrong if the required WR (green) board is installed incorrectly. In some cases, the WR board is set directly on top of the mortar. However, the correct method would be to install the WR board horizontally with the factory-bound edge ¥ inch above the shower receptor or sub pan.
It has been my experience that, in shower construction, WR board can present a future problem if leaks develop behind the board. Under such circumstances, the board will begin to disintegrate and collapse.
But the potential for this type of problem has been greatly reduced since cementitious backer units were introduced some years back. I feel that, despite the small additional cost of the material, cementitious units are far preferable to WR board for tile installations on walls.
Ceramic tile installations are considered permanent ¿ and so they should be. The customer expects durability, and it¿s your responsibility to provide it.
As indicated in Tile Council of America (TCA) detail B-416-2K, the WR gypsum board maintains a ¥ inch gap above the mortar (fig. 2). In TCA detail B-415-2K, when using a cement backerboard, you can rest the backerboard unit upon the mortar (fig. 3).
Finally, when using membranes, it¿s essential that the product directions are strictly followed. For example, the membrane should be turned up the walls a minimum of 3 inches higher than the shower curb, or 6 inches above the floor in showers without curves.