Tiles are the most common finishing surface used in most homes. However, to install them, you need to lay them on a good substrate such as cement boards, but can you use cement board in the shower?

Generally, cement boards can be used as shower backing. They can withstand high moisture and water exposure without rotting, warping, or deteriorating. They also do not promote the growth of mildew and molds, making them the best substrate to use with tiles.

In this article, we will look at cement boards, explain if they can be used in a shower, and discuss how they can be installed. We will also highlight the best cement boards for the shower. By the end of the article, you should have a better understanding of whether you can use a cement board in the shower.

What is a Cement Board?

Cement board is a type of concrete backer board consisting of a fibrous reinforcement with a cement composition (fiberglass mesh and cement slurry) molded into sheets. It is extremely hard, porous, and waterproof, making it a good bond for mortar and grout. It won’t deteriorate over time if exposed to water, making it perfect for use in areas susceptible to the effects of moisture.

Typically, cement board comes in 3 ft by 5 ft sheet panels with varying thicknesses. However, most cement boards are either ¼ inch, ½ inch, or ⅝ inch in thickness. Although it is not an expensive product, it should be used appropriately.

Cement board has the following pros:

• Easy to install and to work with
• Can be cut and drilled with common tools
• Long-lasting
• Withstands moisture and water
• Not susceptible to rot, decomposition, or mold
• Add stability to finishings like tiles resulting in higher load capacity and fewer cracks

Can You Use Cement Board in Shower?

You can use cement board in the shower for the following reasons:

• It will not encourage the growth of mildew and molds
• It can be exposed to moisture and water without rotting, deteriorating, decomposing, or warping
• It is a perfect substrate to use for tiles that are commonly installed in the showers

Is Cement Board Perfect for the Shower Walls?

Cement boards can be used for the shower walls as they can withstand a high amount of moisture and water contact without growing molds, rotting, or otherwise deteriorating. Additionally, they are impact-resistant and form a sturdy base for porcelain, ceramic, and stone wall tiles.

Cement board is a widely-known and commonly used backer board for shower walls. It bonds well with cement, adhesives, and grout and is typically available in 3 ft by 5ft sheets, which perfectly compliments the size of the bathtubs and shower stalls.

Can You Use Cement Board for Shower Floor?

Although you can use a cement board on the shower floor, it is not recommended. It is difficult to achieve the proper drainage slopes and seal the floor to wall seams.

For instance, if cement boards are not installed properly, water can leak into the shower subfloor and damage it. Instead of using the cement board, many shower floor installers recommend making a mortar shower pan or using a manufactured shower pan, both of which can be installed and covered with tiles.

However, if you decide to use a cement board on the shower floor, it needs to be at least ¼ inch thick. You should also ensure that there will be no issue concerning any additional floor thickness. It is important to note that cement boards may not be necessary if you have a concrete or substrate shower floor as you can install tiles directly over concrete.

How To You Install Cement Board in Shower

Installing cement boards in a shower is straightforward. However, you must ensure that you have assembled all the necessary tools and follow the installation steps. There are also safety tips that you need to follow.

Tools and Materials Needed

Installing cement board in a shower requires the following tools:

• Cement board sheets. Usually, they are ¼ or ½ inch thick
• Cement board screws
• High-quality and reliable cordless drill with carbide bits and holesaw
• Thinset mortar
• Mortar mixing supplies, which include a clean 2 – 5 gallon bucket, water and a long mixer attachment for the drill
• Full-size roll of fiberglass mesh tape
• An jigsaw or skillsaw with carbide cutting blade
• Knives: T-square knife or a 4- to 6-inch utility knife and a straightedge knife
• Protective gear including a respirator or mask, eyewear, gloves, and kneepads
• Trowel: ¼-inch notched trowel and a corner-specific trowel
• Waterproof membrane

Step-By-Step Installation Guide

Once you have all the necessary tools, just follow these step-by-step instructions to install cement board in your shower:

Step 1: Prepare your working area

If you’re installing cement boards for new shower walls or floors, you need to clean the area thoroughly. The floor joists need to be squeak-free and sturdy and the subfloor clean. You also need to dry lay your cement boards prior to fasteneing.

Step 2: Cut your cement boards

You should score your cement boards using a utility knife when sizing and trimming them. Some cement boards come with pre-lined grids printed on them, which makes it easier to score and cut them.

It is recommended to use a jigsaw or skillsaw to make the accurate cuts. Use a drill with appropriate sized bits or holesaw to drill holes for the supply pipes. Wearing protective gear such as eyewear and a mask is vital while cutting your cement boards is recommended.

Step 3: Mix thin-set mortar

Here is how you mix your mortar:

• Wear a respirator or mask.
• Pour water into an empty bucket and add an appropriate amount of thin-set mix. The thin-set should be mixed in small batches. This ensures that the product doesn’t dry before you’re ready to apply.
• Mix water and thin-set until it achieves the consistency of thick peanut butter.
• Allow the thin-set to rest for about 10 minutes.

Step 4: Apply thin-set mortar

Using a grooved trowel, smear thin-set to your work area. This should be just enough for a single cement board at a time.

After laying a thin and even layer, comb the ridges through the thin-set using the notched side of your trowel.

However, it is important to note that steps 3 and 4 are not required if you are installing cement boards on existing shower walls or directly to the studs. In this case, screw cement board directly into the wall studs. However, you should consult the cement board manufacturer on using a moisture barrier between the wall studs and the cement boards.

Step 5: Lay and secure your cement boards

Carefully put your first cement board on top of the thin-set mortar. This should be done while the thin-set mortar is still wet. You should apply it with the embossed or rough side facing upward. This step entails:

• Wearing a set of kneepads to keep yourself steady and comfortable
• Using a cordless drill to secure screws along the seam of the cement board
• Inserting the remaining screws 8-12 inches apart over the surface of your cement board

Step 6: Repeat steps 3 to step 4

This is done until all the cement boards are laid on the entire shower floor or wall. If you are installing cement boards on the shower floor, leave a ¼-inch gap between the wall and the sheets of the cement board.

Step 7: Apply tape to the seams

Using a straightedge knife, apply fiberglass mesh tape along every seam of the cement boards. To tape corner pieces, you need to use a corner trowel to flatten all of the fiberglass mesh tapes to the cement sheet successfully.

Step 8: Apply a second layer of thin-set mortar

Use a drywall spatula or trowel to apply another thin layer of thin-set mortar over the surface of all the taped joints. You should make the thin-set mortar as smooth as possible for a flush shower floor or wall surface.

You also need to give the thin-set mortar enough time to dry and cure.

Step 9: Apply a waterproof membrane

After the thin-set mortar has dried completely, paint 1-2 layers of waterproof membrane or glue a waterproof membrane in place. This provides an extra layer of protection against water that can sip behind the cement boards.

Step 10: Clean your working area

This is the final stage, which entails removing all excess debris from the working area. This includes thin-set mortar and cut pieces of cement board.

Installation Safety Tips and Tricks

Installing cement board is a straightforward process, there are safety tips and tricks that help to ensure seamless installation:

• Operate installation tools with care. Ensure that you follow the individual power tool safety rules. Avoid operating tools that you are not sure how to operate.
• Always put on protective gear. Cement boards and mortar dust can be dangerous to your health if inhaled, so wear protective gear.
• Always read and follow the manufacturer’s instructions. Each manufacturer produces cement boards differents. Therefore, read and follow their instructions during installation.

Do You Have to Apply Waterproof System Over Cement Board in a Shower?

Typically, cement boards are incredibly porous and will allow water to pass through them. Therefore, you will need to apply a waterproofing system over the cement boards when you use them in the shower. This will protect the wall cavities and subfloor from exposure to moisture.

Generally, the waterproofing system used can be in the form of a vapor barrier placed behind the cement boards. You can also apply a sealant or waterproofing membrane on the outer surface.

It is important to ensure that the waterproofing method or system you choose is applied correctly. This is essential if you are using cement boards on the shower floor since water can leak to the rooms below or abutting your shower.

What Size Cement Board Should You Use for Shower Walls? Floor?

Typically, cement boards are manufactured and sold in the following sizes:

• 3 ft by 5 ft sheets that are ¼ to ⅝ inch thick
• 3 ft by 5 ft panels that are ¼ inch thick weigh around 30 poundsand ½ inch sheets from 36 to 44 pounds
• 4 ft by 8 ft panels are also available, however, their weight is difficult to manage for DIY installers

Therefore, the size of cement board used for either shower walls or floor is commonly 3’x5’, but varies with the sheet’s thickness.

You should use cement boards with thickness of either ½ inch or ⅝ inch for the shower walls. This extra thickness is required for spanning the wall studs, and it offers a more solid base for the wall tiles. On the other hand, cement boards used for the shower floor are normally ¼ inch thick as they are supported by the subfloor. However, thicker panels can also be used.

Do You Need to Put Plastic Behind Cement Board?

Plastic can be used as a waterproof membrane behind a cement board. You should waterproof all shower walls before installing tiles. Although cement boards are water-resistant, most are not waterproof. Therefore, you need to apply a reliable waterproof membrane behind the cement board.

One of the most common and effective waterproof membranes that you can use is plastic. However, you should consult the cement board manufacturer about using a plastic barrier between the wall studs and the cement boards.

Conclusion

You can use cement board in the shower to provide a perfect substrate for tiles commonly installed in showers. Furthermore, it is less susceptible to moisture and water and won’t promote the growth of mildew and molds.

Hopefully, you found this article helpful. If you have any comments, suggestions or questions, let us know in the comments section below.