Tiling A Shower -- Below The Surface
It's true, tiling a shower would be easy if not for the hidden parts. The parts that you can't see spell the difference in leaks and waterproof performance. Laying the tiles you see is really no difference than tile laying anywhere else. Here are the tricky parts.
Since showers are high moisture, high water environments, steps must be made to keep the water where it belongs. That mostly means keeping it out over the tile and at least not in the areas surrounding the shower.
Less obvious than the floors are walls and even ceilings. Any leaking that happens in those areas opens the way to moisture getting beyond the shower to hidden spots where moisture may be the start of mold and rot.
That means really that a moisture barrier behind the tile is a must to keep water vapor and water itself out of the areas behind the tile. That barrier must go down before the tile itself and can be as simple as plastic sheeting. Even better, why not go for a special waterproof membrane like the Schluter-Kerdi system liner. What you get is a virtually waterproof liner membrane that stops all the water.
It isn't enough even to use waterproof materials behind the tile. For example, cement board works well as a backer for tile since it resists rot. But it will not keep back water, it just resists rot.
Really key to a shower that works properly is the floor.
It may seem that ceramic tile will hold water, but that notion is false. Water goes right through the floor grout and even through some tiles themselves. That is why a liner below the tile is a must.
The most often used method for installing a shower liner involves laying two layers of mortar with a vinyl sheet sandwiched between. The water that makes it through the floor gets stopped at the liner sheet and funnelled to a special drain. This method works well when done properly but has several disadvantages.
Another alternative uses a special pan built especially for tile installation right over the pan. This takes some tricky material. The pan must be quite rigid or else the tiles laid over the pan will crack and come apart. It takes the right support to keep the tiles together. A standard acrylic shower pan or a fiberglass shower pan is not suitable for a shower base for tile.
The TileRedi system is one leader for tiling a shower without the high skill mortar work. Another very different method comes from Schluter-Kerdi. The latter system provides the option for making a custom shower of any size or shape while waterproofing the whole shower floor, walls and ceiling.
Tiling a shower means more than just laying tiles. It means building a shower that keeps all the water where it belongs.