Cement board installation can be daunting.
Especially if you’ve never done it!
Our previous tutorial shared how to choose the right bathroom backer boards in order to avoid a moldy bathroom.
Cement board is a huge part of a bathroom renovation because it doesn’t contain any organic matter for mold to use as food.
Today, we’ll share how to install cement board in a bathtub surround.
Plus we’ll discuss what materials are needed to do the project correctly.
Let’s dive in.
Here are the supplies you need
- Impact Driver
- Impact Bit Set
- Measuring Tape
- Carbide Cutting Knife
- Cement Board Screws
- Alkali Resistant Tape
- Margin Trowel
- 4 Foot Level
- 2 Gallon Bucket
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Determine Where Cement Board Location
The first step in any cement board project is to determine where you want it.
In our case, Rob (my brother-in-law whose bathroom we’re working on) wanted the cement panels in the shower surround but preferred to have fiberglass faced purple board serve as the top border.
It helps to know the dimensions of a typical cement board panel.
They are either 3 ft by 5 ft or 32 inches by 5 ft.
The manufacturers do this because bathtub surrounds typically have a back wall that is 5 ft long.
And both adjacent side walls are anywhere from 32 to 36 inches wide.
This makes installing cement panels much easier because it involves less cutting.
Ideally you want the cement board to cover any area that will be exposed to water.
I don’t know about you but the front wall that contains the showerhead in our bathtub gets saturated with water.
This is a good reason to choose the 36 inch wide cement panel because it will extend out more and add protection against mold forming on any existing drywall that is paper faced.
Choose the Correct Screws and Joint Tape
When you buy cement board it requires the same installation materials as drywall but with a twist.
You’ll need to buy cement board screws that have a special corrosion resistant coating and are much stronger than drywall screws.
In our prior tutorial we discussed how fiberglass drywall joint tape should be used to make wallboard panels one cohesive unit.
The same principle applies to cement board.
The tape you need to use is alkali-resistant, fiberglass-mesh, and polymer coated.
The polymer coating on the tape protects it from the chemicals in the mortar within the cement board itself.
This tape can also be used where cement board and drywall meet each other.
Instead of using drywall joint compound to embed the tape in the cement board you should use thin-set mortar.
We utilized the same thin-set that will be used to attach the tiles.
Having the cement board, alkali-resistant screws & joint tape, and mortar will get you one step closer to installing the tub surround the right way.
Start With the Back Wall
We installed the upper back wall panel first.
Since the width of the back wall was a little more than 5 feet wide we simply installed a full panel without having to trim it.
I spaced the screws on the studs about 8-10 inches apart from each other.
Attach screws at most 1/2 to 1 inch from the edge of the cement board.
Otherwise, the cement will crack.
I prefer to add screws to the top of the cement board then use a level to trace a vertical line indicating the stud position behind the cement panel.
Unless you’re Superman or Superwoman it’s hard to see through cement and this step makes me feel better about the screws being directly centered on the studs.
To make the process easier I highly recommend using an impact drill/driver like this Ridgid I’m holding.
This is hands down my favorite tool and if you’re doing any DIY projects you need to buy an impact driver.
The Americast bathtub we installed had a good 1 inch lip on it, which we attached to the studs using galvanized roofing nails.
We also shimmed out the walls with 1/4 inch lath strips so the cement board would sit flush with the lip or slightly beyond it. This same method can be used for Wedi, KERDI-BOARD, or Hydro Ban Board.
This will allow the tiles to rest beyond the lip of the tub when we secure them to the cement board later in the project.
I measured the distance from the top of the nail (holding the lip to the stud) to the bottom of the upper cement board panel and subtracted an 1/8 of an inch.
This gave me the size of the bottom cement board.
It’s important to get this measurement correct because it’s tough to cut 1/2 inch from cement board!!
Once we obtained the height of the bottom cement board panel I cut it using a special carbide tip knife and the straight edge of my level.
Since the cement board is sandwiched between fiberglass mesh tape it needs scored until the mesh is fully cut.
I scored one side of the cement panel until the mesh completely severed.
Then I bent back the scored portion of the cement panel to expose the other side of the mesh tape.
You can either cut the tape with the carbide tip knife or cut it with scissors.
The lower cement board panel was installed just like the upper portion, and rested just above the lip of the tub.
One big tip is to make sure the tapered edges of both the lower and upper panels abut each other.
This is super important because it provides a recessed space for the joint tape to sit in.
Otherwise, you’ll have a hump at the joint and this will cause your tile installation to be uneven & look bad.
Our back wall was pretty simple to install.
The two side walls are straightforward as well, but I’m going to explain how we attached them to the studs in our next tutorial. Also, it’s critical to check the depth of mixing valves before installing cement board.
There are some details I feel are really important to share and that’s why there will be a Part 2 to this tutorial.
Hopefully these tips helped.
If you’re interested in an easier alternative to cement board then both KERDI-BOARD and Wedi are great options.
If you’re doing a bathroom remodel and need help, join one of our online courses – they’ll make your bathroom renovation much easier!
Let me know if you have any questions and I’ll do my best to help.