What Type Of Mortar To Use Under Shower Base?

When installing a shower base, it is essential to use the right type of mortar. This is due to the amount of water produced by the shower, and the amount of weight put on the base by the user. You want the base to be supported. So, what type of mortar should you use underneath it? We’ve done the research to answer this question.

The best type of mortar to use underneath a shower base is a mixture of Portland cement and sand. This mortar will both support the weight of the shower and provide a barrier that helps prevent water damage to the floor underneath. 

When it comes to putting this type of mortar under a shower base, you can either buy it already mixed (add water) or make your own. In this article, we’ll discuss why mortar is necessary underneath a shower and how to use it for that purpose. Please continue reading to learn more.

worker adding mortar to the underside of a ceramic tile before setting. What Type Of Mortar To Use Under Shower Base

What Do You Put Under A Shower Base?

First things first, let’s differentiate between a shower base and a shower pan to eliminate any confusion. The shower base is essentially the components you put on top of the subfloor to provide structure for the shower. The shower pan goes on top of the shower base and is what you stand on to take a shower.

With that being said, there are four components that you make up the base of the shower. What you’ll need to install depends on if you’re replacing the shower or building a completely new shower from scratch,

Shower Curb

The first component is the shower curb. This is essentially the foundation of the shower and usually consists of a layer of 2 x 4s or bricks that are mortared on top of the subfloor. It provides a layer of additional structure on top of the subfloor to support the weight of the shower.


Next is the pre-slope. This layer of mortar is applied on top of the curb that allows the shower pan to slope downward so that the water can drain out of it. The way that pre-slope works is you apply it in a thinner layer around the drain and a thicker layer as you move away from the drain towards the walls of the shower. (If you’re replacing your shower pan, you won’t need to install the curb and pre-slope.)

See more: Where Should The Drain Be Placed In A Shower?


Then, you need to install a waterproof liner or sealant on top of the pre-slope. This will ensure that any water that should seep through the shower pan (particularly with tile) does not penetrate through the floor and goes to the drain instead.

Click here to see this shower pan liner on Amazon.


Finally, you will need to apply another layer of mortar on top of the liner. Mortar provides more structural support (provided you use the right type) and also helps to keep water from getting underneath the shower. Then, you can install the shower pan or tile on top.

Do You Need Mortar Under A Shower Base?

What Type Of Mortar To Use Under Shower Base

Installing a new shower can already take a couple of days, and now you have to extend that time even longer by applying mortar and having to wait on it to dry? It can be somewhat inconvenient, especially if that’s the only shower you have in your home. Trust us; we get it.

But applying mortar under a shower base is not a step that you want to skip. Depending on the shower pan you are installing, it can crack due to stress or weight.

If that does happen, mortar adds an extra layer of protection that supports your shower and keeps moisture from getting onto the subfloor underneath. So to best answer this question, yes. You do need mortar under a shower base.

What Type Of Mortar Should You Use Under A Shower Base?

There are many different types of mortar out there. Don’t be overwhelmed by all of the choices because only one type works the best underneath a shower. All you need to do is look at the ingredients and make sure that it is a mixture of Portland cement and sand. Other ingredients are okay, too, as long as those are the main ingredients.

There is commercial cement and sand mortar mixes that you can buy, or you can buy the sand and cement separately and make your own. Commercial mortars are recommended because they tend to be stronger and are proven to work. If you opt to go with a commercial mortar mix, you’ll add water following the instructions on the packaging. 

If you can’t find a commercial mortar mix in stock near you for some reason, you can make your own. This will require more work because you have to mix the cement and sand yourself. But, it is an option if you’re in a pinch or if you want to save a little money.

To make your own, all you’ll need is a bag of Portland cement and some fine sand. Mix the cement and sand in a ratio of one part cement to five parts sand. Add water and stir until you’ve reached a thick, peanut butter-like consistency.

How Thick Should Mortar Be For A Shower Pan?

The thickness of mortar for a shower pan depends on the type of shower pan you’re installing. There are main ways to install a shower pan. You can either buy a manufactured one made from various materials, or you can lay tile instead.

If you buy a manufactured shower pan, you will install it right on top of the mortar. The exact thickness of the mortar will vary based on the material the shower pan is made of. This information can usually be found in the installation instructions provided by the manufacturer of your particular shower pan.

If you install tile on top of mortar instead of a manufactured shower pan, then the mortar needs to be thicker. This ensures that water has a harder time penetrating through the tile and into the subfloor below. The thickness of mortar when installing a tile as a shower pan should be around 2-3 inches thick and slightly thinner around the drain.

See more: Should You Tile The Floor Or Walls First In A Shower?

How Thick Should A Shower Base Be?

Remember that a shower base consists of different components. Each component adds more thickness to the shower base, but each layer is not the same thickness. Here are the general guidelines for the thickness of each component, but remember that the exact thickness can vary based on the manufacturer of certain materials used.

  • The shower curb is usually between 3-4 inches thick but can vary based on personal preference/materials used.
  • Pre-slope- starts at around ¼ inch around the drain and gets thicker toward the outside of the shower.
  • Membrane- a thin piece of plastic; adds hardly any thickness to the shower base
  • Mortar- between 1 to 3 inches thick, depending on the type of shower pan or tile and manufacturer recommendation

How Do You Mortar Under A Shower Pan?

spreading mortar using trowel for Ceramic tiles installation

Assuming that you are replacing the shower pan instead of building a whole new shower, mortaring under a shower pan is not a difficult task. If this is the case, then the drain, curb, and pre-slope should be already installed. You should need to lay down the membrane layer if it isn’t there already, then apply the mortar.

If you need to install the membrane layer, you will lay it down on top of the existing components of the shower base, then cut a hole out where the drain is. The instructions on the plastic liner should tell you how to do this.

After laying down the membrane, mix your mortar, following the instructions on the packaging. Then, pour some mortar onto the floor and use a flooring trowel to spread it across the shower base. Remember that the thickness it needs to be depends on the type of shower pan you have.

Next, install the shower pan. Place it on top of the mortar and make sure it is level. Shower pans have fins on the bottom that embed into the mortar for structural support. Let the mortar sit for 24 hours before stepping into it.

In Closing

The best type of mortar to use under a shower base and the pan is a mixture of Portland cement and sand. This type of mortar provides both structural support and a water-resistant barrier underneath the shower. Remember to follow the instructions carefully when mixing the mortar and applying it to ensure it works properly. Thanks for reading!

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