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How To Install Cement Board Under Tub? [4 Quick Steps]

You’ve installed your new bathtub in your bathroom. It’s become absolutely necessary to install a cement board under the tub. Don’t know how to do so?

That’s alright, we’re here to help. We’ll walk you through the process.

How to install cement board under the tub? 

You need to follow a few steps for the installation. First of all, you need to determine the location of the cement board. After that, you must consider choosing the correct joint tape and screws. Then you must install the cement board. Finally, you need to move to the final installation part and finish the process. 

This is just a sneak peek of the whole process. To know the whole process, read through our article.

Let’s get started with the installation process!

How To Install Cement Board Under Tub? [4 Simple Steps]

Installing cement board under the tub may sound difficult but it’s an easy process. We have curated a step-by-step process for your convenience. Make sure to follow our instructions properly.

Tools Required For The Installation

Before going to the installation, we must gather the necessary tools. The tools that are needed are mentioned below-

  • Measuring tape
  • Cement board screws
  • Galvanized roofing nails

Once you have the tools, move on to the installation process.

Step 1: Determine The Location Of The Cement Board

The very first thing you need to do is identify the location of the installation. After that, the cement panels in the shower can be surrounded. 

While working with the cement board, you might not be able to use the shower. You may just build a temporary shower in that case. 

The top border should be made of a fiberglass-faced purple board. Because knowing the measurements of a standard cement board panel is useful. They’re 3 foot by 5 ft in size. 

And the width of both adjacent side walls varies between 32 and 36 inches. This requires less cutting, making the installation easier.

Step 2: Choose The Correct Joint Tape And Screws

The cement board requires the same supplies for installation as drywall. But there’s a catch. You need cement board screws here. They must be coated with a particular corrosion-resistant coating because some screws get rusted.

Not sure what screws to use for this? Well, we’ve got here some of our preferred ones below-

Product 1
Product 2

These are the products that are compatible with this installation process. These products are quite long-lasting as well.

These have to be far more powerful than drywall screws. Alkali Resistant Screws are required for cement boards. The tape’s polymer coating protects it from the mortar’s toxins. 

You can also use this tape can on drywall and cement board meet points. Cement board tape is resistant to alkali and can survive the rigors of cement board installation. 

To embed the tape in the cement board, use thin-set mortar. Do not use a drywall joint compound for this. 

Step 3: Install The Cement Board

You need to install the cement board now. Firstly, install the screws keeping a distance of 8 to 10 inches from one another. You’d see that there is a 1-inch lip on the bathtub you installed. Galvanized roofing nails are used to secure the board to the studs. 

Then use 1/4-inch lath strips to shim out the walls. As a result, the cement board would be flush with or slightly beyond the lip. You can waterproof the shower in the same way.

This allows the tiles to rest on the edge of the bathtub. Now measure the distance. Begin from the top of the nail and go up to the cement board bottom. Then peel off 1/8 inch.

This will provide you with the dimensions of the bottom cement board. You need to make this measurement correctly as it is quite important. Because it’s difficult to cut 1/2 inch out of the cement board

Step 4: Final Installation

Now, you will get the height of the lower concrete plate panel. Cut it using a special hard metal knife and a straight edge. The concrete plate is polished between the fiberglass mesh ribbon. 

Vote for one side of the concrete panel until the network is completely cut.  Use a cutting knife of hard metal suggestions and level to cut the concrete slab. After that, double the calm part of the cement panel. 

This would reveal the mesh tape’s other side. You can use the hard metal tip of scissors or knife to cut the tape. You may cut it with an angle grinder the same way you’d cut ductworks with it.

These are the steps that have to be followed to install cement under the tub. Make sure you follow them properly for the best result.


Question: Can the cement board go under the tab?

Answer: There’s the best method when it comes to placing cement boards around a tub. That is to keep the cement board from getting too close to the lip. It should be applied to the wall with the bottom edge about 1/4 inch above the tub’s lip. Then, on the bottom bathtub tile, apply a generous amount of thin-set. After that, move it 1/8 inch.

Question: Is it okay to use cement board screws on drywall?

Answer: Cement boards will not accept drywall screws or nails. Fasteners used for drywall construction are not corroded. This prolongs the service life of cement boards or galvanized fasteners. As a result, you can not use cement board screws on drywalls.

Question: Is it necessary for the cement board to be waterproof?

Answer: Concrete backer-board is likely to be your best option if you need durability and strength. To begin, place a waterproof or resistant covering between the wood studs. Before you install the concrete backer-board, think about it. As a result, the wood studs are protected from moisture absorption through the backer-board. As a result, the cement board needs to be waterproof.

The Final Words

Now, you know how to install cement board under a tub! We believe our steps were clear enough to understand.

We hope you like our quick and simple steps and we wish you all the best with your home improvement!