Now that my drains are in the right places and subfloor is finally finished, I get to start installing the shower walls! I never thought I would use an exclamation mark after a sentence like that…There are quite a few steps involved in this, so let’s just dive right in.
Shower wall material
Have you ever wondered what is behind the tile in a shower? Me neither, however, it was kind of important that I figure it out. Whenever there will be water or moisture present, the walls are made of cement backerboard. This website gives all of the details, but I’ll sum it up quickly. Cement board is not waterproof in itself, however, it does not swell if it gets wet like wood does. While I don’t plan on water getting in, the reality is that it might, and the cement board is the best material for installing shower walls.
I chose the Durock brand cement board because it had the appropriate thickness to match the drywall, which will make it easier to hide the seams.
Cutting the cement Board
For this particular type of cement board, cutting is relatively easy.
First, I measured the length of the cement board needed for each of the walls.
Next, I scored the board using a straight-edge and utility knife.
I bent the board on the line that I scored. The cement board breaks on the line but is still attached with mesh on the other side.
Finally, I cut the other side of the backerboard at the crease. At that point, it just snaps off.
The only area that was somewhat difficult was the cuts for the shower shelf. I had to cut a rectangle out, making the score and snap method difficult.
I used this pre-made shower shelf and was able to find a place it would fit between the studs. I added some 2x4s at the top and bottom so I would be able to secure it later. Then I measured the hole and cut the board accordingly.
After all my cuts were complete, I fitted them to the wall to ensure they were correctly cut. You have to make sure to leave a little bit of a gap for expansion, so when the pieces were too tight, I filed away the ends to get the perfect fit.
Attaching the board to the walls
To attach the boards to the wall, you need a special screw. Click here to see it. They have a serrated head to cut through the cement and are made with a corrosion-resistant finish.
I used an impact driver to screw the board to the studs. The impact driver drives screws using a high torque than a typical drill, making it easier and faster to drive the screws. I attached the screws about 4 inches apart on each stud, which equated to a shit ton of screws. The impact driver made it easier.
To complete the shower wall installation, I just repeated adding a sheet and screwing it in.
I dry fit the shelf to ensure a good fit. I had to file away the edges for about an hour but eventually made it work.
One wall down, 2 to go.
Cutting holes in cement board
The rest was pretty similar except when it came to cutting the holes for the shower and tub faucets.
Here, I measured the distance from the edge of the boards to the center of each hole. Then, I used a hole saw to cut the holes in the cement board for the faucets.
I accidentally cut the holes on the wrong side, but a quick google search told me it doesn’t matter which side of the cement board is exposed. Whew!
Next, I repeated this process for the bathtub faucet.
All that was left to do in this step was to attach the remaining boards. This process wasn’t extremely difficult, it was just really time-consuming, and sometimes frustrating trying to get the boards to fit.
Sealing the seams
Now I had a massive amount of cement backer board screwed into the walls, which means I had a ton of seams to seal. Thin-set mortar here I come…
Mixing the mortar
Mixing mortar can be somewhat of an art, so I have learned.
I had a 50 lb. bag of thin-set and definitely did not want to mix it all. The proportions for mixing mortar and water is dependent on the weight of the mortar, so I had to weigh it. In general, you should mix 1/2 cup of water for every lb. of mortar.
Once I weighed the thin-set, I added the appropriate amount of cold water to another bucket and slowly added the thin-set while mixing with a paint mixing paddle. The consistency should be that of creamy peanut butter.
Sometimes, you have to add a little more thin-set or water to get it to the correct consistency.
After mixing, you must allow the mortar to sit for 5 to 10 minutes so that the additives have enough time to activate. You are left with something that looks like this.
Applying thin-set to the backerboard
Before you start slopping on the mortar, you need to apply fiberglass mesh tape to all of the joints. As the name implies, it is stick on one side and you simply stick it to the wall making sure there are no bumps.
Whenever the joint met the drywall, I used a level to ensure the lines would be level and plumb (straight up and down).
On the corners, I used a trowel to make sure the tape fit securely.
Applying Thin-set to the Shower Walls
Then I smeared the thin-set onto the seams of the backerboard and smoothed it out to be as flat as possible.
For the shower faucet area, I used Kerdi-Schluder pipe seals. They have a rubber opening that seals off the area where the pipe comes out of the backerboard and a waterproof membrane encircling the seal. I used an unmodified thin-set (according to their installation instructions) to seal the membrane to the pipes.
After applying the thin-set to all of the shower walls, I applied additional thin-set to screw holes. I have walls again!
Finally, I did the same thing with the wall that will surround the bathtub. Almost done!
Waterproofing the walls
The thin-set needed to cure for at least 24 hours. I gave it a good 48. The last thing left to do was to waterproof the cement backerboard.
I used Redgard Waterproofing membrane to waterproof the cement board. It has a pudding consistency and is a little tricky to apply.
I moistened the walls, as per the instructions, used a paintbrush in the corners, and rolled on the rest. Because it was so thick, it was hard to get the membrane into the little pinholes of the backerboard.
I ended up mixing a little water into the membrane to make it more viscous. This helped a lot.
Because I added water on the first coast, I did a second coat without modifying the membrane.
Now the shower walls are officially waterproofed!
Installing the shower shelf
Installing the shower shelf was pretty painless. First, I applied a bead of silicone to the flange of the shelf.
Next I added screws in the holes and applied a layer of thin-set. You have to try and feather it out so it is as flat as possible.
After the thin-set cured, I applied the waterproofing membrane. And I am done with installing shower walls!
Look, I can’t see any studs… Except for me of course. Next up, prepping the floor for tile!