Tiled Showers 101

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Retired Defense Industry Engineer xxx
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New England
First, a few basic concepts:

  • The shower pan has a waterproof layer and plumbing code requires it to be sloped to the drain at a minimum of ¼” per foot – it cannot be flat on the floor

  • Tile is not waterproof, it is the decorative, wear surface

  • The shower should not be damaged if used prior to installing the tile, but normally you couldn’t do that since it would contaminate the surfaces making it hard to impossible to tile it, but not because it would leak

  • The shower pan is not allowed to have any fasteners through it lower than 2” above the top of the curb

  • The shower pan must not leak during a flood test

  • Vertical surfaces in a shower above the pan do not have to be waterproof, but must be made of materials that are not affected by moisture (a common one is a cement backer unit – cbu)

  • A shower wall should include a vapor barrier, either behind it in front of the studs, or a topical one directly underneath the tile (this typically requires waterproofing the walls and the pan instead of just the pan)

  • A properly built shower should not ‘fail’, IOW, it should last until you get tired of it and want to remodel which could be many decades.

  • The industry calls for a flexible joint at all changes of plane (i.e., from horizontal to vertical, or in a corner of vertical walls) and grout is not flexible.

  • Unless using a linear drain, it is best to have your drain located in the middle of your pan

  • While not required, most people find the aesthetics of a shower more pleasing if the bottom row of tile is level all around the shower

  • If your drain is not close to the middle of the shower, the slope can end up quite steep if you maintain the level first row on the side(s) closest to the drain to keep the ¼” per foot minimum

  • Using a highly irregular tile like pebbles drains better if your slope exceeds ¼”/ft
  • Unless your shower is round or a square, when your drain is centered, to keep the minimum of 1/4"/foot slope, the shorter wall will have a steeper slope to the drain when your perimeter is level

  • Unless using a linear drain, or you have a very carefully constructed shower pan, to keep lippage of the tile edges from being an issue, a tile 4x4” or smaller usually works best. Using larger ones can be done, but it takes special layout and pan prep. The setting bed of the pan tends to end up a bowl, rather than one or four flat surfaces, and bigger tile will not conform to the bowl shape without their edges being uneven in height (lippage).

  • Grout lines tend to add grip to the tiled surface which is another reason why smaller ones (more grout lines) works better on a shower floor.

  • As you go up in size on tile for the shower floor, the wet coefficient of friction should also go up to keep things safe

  • Limestone and marble in a shower can be etched by many things: your water may be slightly acidic, some cleaning materials can damage these materials, as can some shampoos, conditioners, or soaps.

  • Some stones can absorb moisture which will cause them to change color and may take weeks to return to their dry coloration – some should never be used in wet areas

  • Grout/tile sealer is primarily to help with cleaning…while it may help slightly with moisture, it is more to help prevent dirt and oils from penetrating deep.

  • A typical porcelain tile does not absorb any sealer, but you may still want to seal the grout

  • Some stone tile can permanently change color with some sealers

  • While sealers can last a long time, they generally are not a ‘forever’ thing, and may need to be reapplied periodically

Building a successful shower isn’t technically hard but is very detail oriented. Skipping or failing to follow all of the approved steps can lead to failure down the road, sometimes in short order, sometimes after a number of years.

The Tile Council of North America (TCNA) prints an updated annual standards book, lessons learned are included in the new versions so they are not static – the recommendations change for a reason, for whatever reason, either the old method was found to fail in some circumstances, or the materials may no longer be available. It lists many different ways to build a shower. You should pick one method and follow it. It also references some ANSI standards, so if you are not familiar with those, you may need a copy of those as well to fully comprehend what needs to be done when building a shower. There are pros and cons to each method, but all should provide a reliable shower if the instructions are understood and executed with good workmanship. Mixing parts of various methods is not guaranteed to work and should be left to a professional with experience or at the minimum, consultation with the associated manufacturer of the products involved.

This could go on to become a book, but experience really helps. If you are willing to read and can understand, and open to fail, then fix things, most people can build a working, reliable shower. Then, there are people that can’t screw in a lightbulb, but even they often can benefit by learning what works and doesn’t, and checking with the installer.

If you fall for the “I’ve been doing it this way for decades, believe me, it will be okay” and you find it conflicts with the TCNA guidelines, that should run up a big red flag. It MIGHT work, but there’s more chance that it won’t. There’s often more than one way to do things that will work, but again, you need to cross all of the T’s and dot all of the I’s to end up successful. It’s cheaper to do it right the first time than tear it out to fix it and do it again. Good workmanship relies on proper prep on most of the parts you cannot see when finished – those backbones MUST be done properly. A great looking shower may be a disaster if what’s underneath isn’t done properly. Some people are great craftsman at setting tile, but don’t have a clue on what’s required to make it last and perform properly…you really want the whole thing done right. If you do, whether you do it yourself, or pay someone to do it for you, you’ll be much happier with some knowledge and research beforehand.

Some places (much of Europe) have apprenticeships and licensing schemes before you can call yourself a tile man. Most places in the USA do not require any training to advertise as a tile installer. There are some certification programs, and it might be worthwhile searching out someone that has passed their series of tests. Some really mean well, but just don't have a clue. You don't want to be caught in their hype, and again...most of the really important things in a shower are underneath the tile. Obviously, you want it to look good, but you really want it to actually look good and perform reliably...that's what the TCNA guidelines are based on, and if followed, will produce. If having it done, you may want a line in the contract that says that the shower will be installed per TCNA guidelines.
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