The Tile Shower Pan -- Why One Layer Is Too Few

Published: 16th September 2009
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The tile shower pan keeps the water where it belongs. See, a shower floor just naturally leaks, no way around it. That's because the grout and even some tiles are not waterproof.
The key to a waterproof shower is getting the waterproof membrane installed the right way. For a trouble free shower, the waterproof liner must be right.

One key to the membrane working is the first mortar layer.

Some installers only use one layer of mortar when building showers. That's a really bad idea. Here's why it is.

The real trick to a tile shower is the waterproof liner membrane that's installed in the mortar shower base. Now you can put down the membrane on the subfloor, attach it to the drain and then lay on the mortar base for the tile. Here's the problem...

If the liner is flat or if it sags, that's a pool in the making. It's a pool within the shower floor. That water seeps into the mortar base all the way down to the waterproof membrane. The membrane than routes the water to the special drain.

If the liner forms a pool, that's an ideal place} for mold to begin. Mold can grow and actually saturate the whole shower base. Plus, a constantly wet shower base slowly deteriorates. This is double bad.

To avoid that water accumulating within the shower base, the liner must slope to the drain. That way all the water that makes it to the membrane just flows down to the drain and away from the shower.

That's where the two layers of mortar are important.

The first layer of mortar is put down over the subfloor and is sloped at one-fourth inch per foot right to the lower drain base on the shower drain. The liner is sealed to the drain base and you're set. The liner then is at the proper slope and sealed to catch all the water that makes it into the shower base.

The pre-slope masonry layer is critical for a tile shower pan that lasts. It's a simple step and should be part of a shower pan. Shower floors just naturally allow some water through the floor. The liner membrane is the trick to getting rid of that water. Take the time to get the liner in the right way.

A tile shower base is built in layers. The first mortar layer is often left out and that is a very bad idea.

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