Installing tile on walls can be more challenging than working on floors—this is where your skills as a tile installer will truly be tested. Not only are you battling gravity, but there are also plenty of obstacles like windows, doors, niches, and columns that will add to the difficulty. Flat and plumb walls are key to both a good-looking and long-lasting installation.

 Properly prepared walls make your job easier, as they reduce the need for adjustments. When your walls are plumb, the cuts from top to bottom will be uniform. However, if your wall is uneven, every cut will need to be tapered, which adds significant time. This is especially noticeable with smaller tiles, where any inconsistencies in size can catch the eye. 

Oscar Barradas, owner, OBF Tile, installing wall tile in a bathroom project. Photo: Oscar Barradas.

I have a variety of level sizes that I use from my torpedo level all the way to a massive 8’ level. You always want to use the level that's the closest in size to the height of the wall you’re checking, for example, checking a 10’ wall with a 16” level would not give you accurate information on whether the wall is plumb or not. 

You've checked every stud and they're all plumb, but are they all on the same plane making the wall flat or are some of them sticking out more than others? To check this, use a level or straight edge across the wall, and this will tell you whether your wall is flat or not.

There are many ways to fix walls that aren’t plumb and/ or flat, but I’m going to focus on two of my go-to methods.

First up, we have wet shimming. This method consists of generously applying thin set to the face of the studs, then pushing the board into the studs until it’s plumb. Once you’ve reached plumb, you can add some fasteners temporarily to keep it in that position while the thin set dries. Usually, the next day you can then drive all your fasteners into the board that is now flat and plumb.

The second method is my favorite—foam shims.

A company based in Houston, Texas, came up with a set of foam shims in various thicknesses from 1/16” to ½" in 1/16” increments. The system includes a gauging tool that helps you determine what size shim goes where.

Shims are placed on every location where you will be adding a screw to the board, so you need to mark your studs before adding the shims. Once you have added all the shims, you can screw the board in place and voila! I prefer this method simply because I don't have to wait till the next day to screw my board in place, but both methods will give you the same results. 

Wall tile installation can seem intimidating, but if you focus on preparing your walls properly, the process will be much smoother and the results will be worth the effort.