The most common cause of a problem with a tile shower occurs when the pan – the bottom of the shower, where the drain is – fails to properly hold water. When this occurs, the only real recourse is to replace the pan before the leaking water can do major damage to the structural framing of the floor it's sitting on.
One course of action is to replace the entire shower, walls as well as pan. This results in the cleanest installation and the best assurance against future leaks. It's also the most expensive type of repair, so it's also well worth exploring the possibility of replacing just the pan.
The shower pans in use today are constructed using a thick, heavy duty PVC liner. The liner comes in sheets, and is custom-fit to the wooden framing that makes up the shower, extending approximately 12 to 18 inches up the wall. A two-piece drain fitting is used, with one half of the drain above the pan liner and the other half below, sandwiching the liner between them to form a water-tight seal.
After completion, the pan is tested by filling it with water and allowing it to sit for 24 hours to check for leaks. After that, mortar is applied to slope the pan from all sides down toward the drain, then tile is installed over the pan and onto the walls. The tile overlaps the pan liner, again to help ensure water-tightness.
Removal of the pan requires that the tile on the lower part of the walls be removed, up to a level above the top of the pan liner. This is typically done by using a diamond wheel on a small grinder to make a horizontal cut through the tile on the sidewalls of the shower, approximately 24 inches up from the existing pan. Wall tile is carefully removed to a point above where the pan liner stops, then all of the tile and mortar in the pan itself is removed.
Once everything has been removed, the tile contractor will inspect the framing for moisture and damage. Any unsound wood is replaced, and the entire floor area is dried before proceeding. Finally, the two-piece drain fitting is replaced, a new PVC pan liner is installed, new mortar is installed over the liner, and new mortar or cement board is installed on the walls to cover the liner and get ready for the new tile.
Now, of course, you have the problem of what to do about the tile. It's very unlikely that you will find a new tile that will exactly match the old one, and you may end up with tiles that are one or two shades off from the original - which really accentuates the fact that a repair has been made. Instead, most tile setters will opt for a complimentary or contrasting tile on the lower rows and on the pan, which can really look nice when properly coordinated.
Another option open to you is to use a prefabricated fiberglass or acrylic shower pan instead of one custom made with a liner and tile. Prefabricated pans come in several standard sizes, and if the dimensions of your shower match up with one of these pans, you can save both time and money with this approach.
Initially, removal of the old pan is done in the same manner as outlined above. The new prefabricated pan is then installed, as is a new drain, which is a different type from the one used with the pan liner. Finally, new tile is installed on the walls so that it overlaps the new pan.
In most instances, neither of these repairs is really suitable for a do-it-yourselfer. Instead, look for reputable, licensed tile contractors who have experience with pan repairs, and discuss your options with them.
