Confused About Mortar Under Tubs

If you are about to have any new household device installed in your home, you need to do some research first. We all know how a bathtub looks and works but do we understand the detailed mechanism behind it? 

For this reason, we would like to talk in detail about mortar beds as many homeowners are easily confused about mortar under tubs when they first heard of it. So, let’s not waste any more time and keep reading to find out more.

What is mortar under tubs?

If you haven’t known this yet, just the bathtub alone will not be able to support itself when it has to carry the human body weight, as well as the weight of the water. 

Without something to stabilize the position of a bathtub, it will move around or even break because the casincannotnot support the weights it has to carry. Due to this, it is very unsafe for you to install a bathtub without any of its supporting parts.

From that, we introduce the mortar bed. It is a base built around the bottom of a bathtub to provide a stable foundation for the heavy tub. Hence, it will prevent all the issues that we’ve mentioned above.

If you are still puzzled, then here is a picture to have a clearer view of the mortar bed.

Kinds of bathtub that need a mortar bed

Bathtubs have become more evolved, and few in the market don’t require a mortar bed. Although, in most cases, the mortar bed is still necessary when installing a bathtub. Here are the most popular types of bathtubs that you can look into.

Acrylic bathtub

It is a fundamental requirement for an acrylic bathtub to have a mortar base. This is because the bottom part is quite vulnerable to an abnormal amount of weight. After some time, without any support, the tub would bend and crack.

Plastic bathtub

Plastic bathtub is especially vulnerable to breakage, so a mortar bed is a must when installing this kind of bathtub.

Steel bathtub

A steel bathtub doesn’t need a mortar bed unless the floor level of your home is a bit uneven. Otherwise, mortar is optional for the steel bathtub.

How to install mortar under tub 

Block and brick mortar 

Out of all the mortar types, block and brick mortar has to be the most common one. To make block and brick mortar, you will need an even mixture of sand and cement, add some water to the mixture, and there you have it, a mortar base. The mixture is supposed to be thicker to set bricks and blocks.

Now, you will use that mortar as a “glue” to set the bricks. If you like, you can put sheets of plastic on top so your bathtub would be removable, just in case you want to remodel your bathroom.

Ready Cement

This one is probably the easiest one to make. It is just a blend of cement and water. To make the cement mortar base, you will need all-purpose cement, which you can find at any home improvement store. 

After that, you mix the cement with some water, just enough to form a thick, creamy texture.

When you have your mortar mixture ready, you spread a layer of mortar beneath the bathtub. Then, fill it with water so the mortar can form around the bottom of the tub.

Custom mortar mix 

This kind of mortar mix is supposed to be the most budget-friendly in the list. This mortar contains four shovels of sand and one shovel of cement. Afterward, you dry mix the two components, mix them well so the sands and the cement will combine evenly. Finally, you add in some water, and just like the previous recipe, you only need to add the right amount, so the blend is thick and creamy. 

While mixing this, you can do it right in the tub frame, so you don’t have to waste time transferring the mortar from a bucket into the frame. When you’re done, you can put the bathtub on top and wait for the mortar to dry. 

Drywall mud 

Drywall mud is not commonly referred to as a mortar but people can also use it as a bathtub base. This one is pretty simple. You can buy a container of pre-mixed drywall, add in water. As a result, you can have a completely effective mortar base.

The setting is no different from any other mortar base, and you can even spread a plastic sheet on top to prevent mortar sticking to the tub. This way, the bathtub can be removed for any future innovation.

Confused about Mortar under Tub – Tips for You

How long does it take for the mortar to dry?

The time depends on the temperature and the humidity. But normally, it takes about 12 hours for the mortar bed to dry.

How deep should the mortar be?

There’s no exact depth for a mortar; you can eyeball it. Usually, the mortar should reach a few inches of the tub’s stands for stability. To be more specific, you’d like the mortar to form a barrier around the bottom part.


That is all you need to know about the mortar bed. If you were confused about mortar under tubs, we hope that this article has answered some of your questions. No matter how even your floor level is, a mortar bed provides an extra boost in durability. So, keep this in mind when installing a bathtub in your home. Best of luck!

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