Shower Pan Replacement

• Shower Pan Liner Replacement – Ceramic and Marble Tile Showers

- John P. Bridge

Ceramic tile showers that are properly built contain a waterproof barrier (shower pan liner) under them that catches water transferring through the tile floor and directs it down the drain pipe. You can’t see the shower pan liner after the shower is completed, so you don’t know what type of material it’s made of. And, too, you can’t determine whether a shower pan liner was even installed at the time of construction.

Ceramic and marble tile showers are not waterproof: they are water-repellent. Under the tiled floor surface about two inches of cement mortar is usually found. The pan is under the mortar. When you begin using the shower, the mortar becomes saturated with water and remains that way as long as the shower is used regularly. In essence, when you take a shower, you displace the water already in the floor with new water. There are small “weep holes” at the base of the drain fixture that allow the water to move down the drain pipe.

Shower “pans” have never been actual pans. They are, rather, fabricated on the job from some sort of flexible waterproof material. The material is laid on the sub-floor, brought up the side walls to a point slightly above the top of the curb (dam), and folded in the corners in what is referred to as a “hospital fold.” No cuts are made at the corners. A hole is cut where the pan joins the drain assembly.

Among the various materials shower pans are made from is lead sheeting. The life of a lead shower pan averages 20 years or so, after which the lead will have oxidized to the point that it is nonexistent in places. Eventually the water that gets beyond the pan spreads toward the walls and their wood framing. Although lead was the best material available for years, it is no longer the material of choice.

There are a number of other materials that have been used for shower pan fabrication, but all of them deteriorate as fast or faster than lead.

That brings us to PVC (poly-vinyl chloride) shower pan material. PVC is the best material yet to be used. At a thickness of 40 mils, a PVC pan will last virtually forever. The material has been around since before I entered the trade 30 years ago, and as far as I know, no PVC pan has ever rotted or otherwise failed.

If your shower develops a leak at its base, there is a good chance that the shower pan has failed (or was not installed correctly) (or was not installed at all). After you have determined that the leak has nothing to do with the door opening (often the case), you should call a plumber to have the shower pan tested, or test it yourself.

The pan is tested by plugging the drain and filling the base of the shower with water (about 2 inches). One trick is to use a small party balloon as a plug. Inflate the balloon to a diameter slightly larger than the drain pipe. After removing the hair strainer, push the balloon down the pipe. It can later be punctured and allowed to go down the drain. The weep holes at the base of the drain are about 2 inches below the surface of the floor, so the balloon (or other plug) must be pushed down at least that far.

When you are satisfied the drain is thoroughly plugged, put in about two inches of water and place a pencil mark on one of the walls at the water level. The water is left in overnight. If the level of water goes down, the shower leaks. Of course, you will probably also detect wet areas outside the shower.

If the shower is built of cement mortar (mud), you can opt for a shower pan replacement rather than replacing the entire shower. If your shower has nothing more than sheetrock behind the tiles, now would be a good time to completely rebuild it using the mud method. It doesn’t make a lot of sense to me to perform a major repair on a shower that was not built properly to begin with. Damage to a “sheetrock shower” almost always extends far above the shower pan area.

Changing a shower pan must be considered radical surgery. It is a halfway measure, but it works. The entire floor is torn out, along with most of the curb and the lower portions of the walls (usually 2 or 3 rows of wall tile). After the new pan has been installed, the bottom of the shower is rebuilt using new materials.

Where new tile meets old, there will be a “cold joint,” meaning the new and old portions of the shower are not attached to one another. This joint may have to be filled with caulking if there is any future movement of the shower, however slight.

Additionally, the new tile will not match the old, even if the original (leftover) tile is used. Wall tiles can fade through the years, and existing tiles will usually contain deposits of waterborne minerals and soap products. In many instances the original tiles will no longer be made. Whatever the reason, understand that the new shower bottom will not match the rest of the shower. Accept it, or choose to have the entire shower re-done with new tile.

I have posted some pictures of the pan (liner) installation process at:

See also: Kerdi Showers

For additional information or advice on shower pans, join us at the John Bridge Tile Forums.

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