Can You Use Redgard Over Mortar Bed? (Explained)

Constructors used mortar beds before concrete boards became popular. Mortar beds comprise thin concrete mortar areas that are often created on top of wooden subfloors.

The purpose of a mortar bed is mainly to give tiles a suitable surface to bond to. On the other hand, RedGard is a liquid waterproofing membrane that is highly beneficial in stone and tile applications.

Considering the benefits provided by these two building materials, you may decide to use RedGard to waterproof your mortar bed. But is it advisable to do so? Keep on reading to find out.

mortar bed

Should You Paint RedGard Over Mortar Bed?

RedGard is one of the most effective waterproofing membranes on the market. If you are considering tiling over a mortar bed, it’s a good idea to paint RedGard over it.

Besides waterproofing the mortar bed, RedGard will also prevent the cracking of tiles. You will therefore enjoy two benefits at once.

When using RedGard over a mortar bed, you need to keep a couple of factors in mind. First, the mortar bed should be allowed to dry fully before you can paint RedGard over.

Secondly, the RedGard should also be cured before you start tiling over it. This will ensure the project lasts long.

Please note that these rules extend beyond the RedGard waterproofing membrane. It doesn’t matter which waterproofing product you are using. The surface of the mortar bed ought to be completely dry before you can paint RedGard over it.

Will RedGard Create a Moisture Barrier Over Mortar Bed?

There are several concerns associated with applying RedGard over a mortar bed. One of them is creating a moisture barrier.

Most moisture beds, especially if they are being installed in a shower. They often feature a waterproof membrane at the bottom. The most commonly used membrane is a vinyl liner.

When you waterproof the surface with RedGard, and there is a vinyl liner at the bottom, you will create a moisture sandwich.

That can be very problematic for the mortar bed because too much moisture can cause it to deteriorate sooner than anticipated.

RedGard will create a moisture barrier, but only if there is a vinyl liner or a waterproof membrane below the mortar bed.

Is a Mortar Bed Waterproof?

Not really. Similar to other building materials, mortar beds also have to be waterproofed to protect them from the effects of moisture.

Mortar beds can benefit significantly from a waterproof membrane and a special drain channeling the water away from a pan. Waterproofing a mortar bed is crucial if you want the project to withstand the test of time.

Will RedGard Offer More Protection to a Mortar Bed?

If applied correctly, RedGard can waterproof the mortar bed and, in the long run, protect the ingredients from moisture damage.

However, understanding the effects of waterproofing the top of the mortar bed is crucial if you already have a waterproof membrane at the bottom.

Does RedGard Prevent Mold Growth on a Mortar Bed?

If the mortar bed is exposed to moisture frequently, you must be mindful of mold growth. Mold thrives in damp areas. However, with RedGard, you will prevent the entry of moisture below the mortar bed.

That will ensure even if water passes through the grout, it won’t seep through the mortar bed.

How Long Should Mortar Dry Before Applying RedGard?

Earlier, we emphasized letting all the materials cure first before applying something else on top of it. If you are building a mortar bed and want to waterproof it with a RedGard membrane, you shouldn’t do it too soon.

The ideal time you should give a mortar bed to dry before RedGarding is 48 to 72 hours. Within that period, all the ingredients in the mortar bed will have fully cured, and then you can install a waterproof membrane.


How Many Coats of RedGard Should Be Applied Over a Mortar Bed?

Custom Buildings, the manufacturer of RedGard, recommends two coats of this product to be applied over any substrate.

Two coats are enough to create an impenetrable layer on the surface that will block moisture and water. When assembling materials, make sure that you buy enough RedGard to cover the surface of your mortar bed.

How Long After RedGard Can You Tile Over Mortar Bed?

It would be best if you waited for the same duration as you did with the mortar bed. Another 48 to 72 hours will ensure that the RedGard has fully dried over the mortar bed. RedGard is often pink when wet and red when dry. Be on the lookout for these color changes.

Isn’t RedGard Only Supposed to Be Used on Walls?

If you have hired somebody to install a shower in your home, you may be shocked when you find them painting the mortar bed with RedGard as well. Since this is your home, you will be concerned about the effects of adding another waterproof membrane.

Most people are accustomed to using RedGard on the walls. But what most people don’t know is that RedGard can also be used on the shower pan or mortar bed.

If a mortar bed is exposed to a lot of water or moisture, a layer of RedGard will waterproof the surface and prevent the bed from becoming wet or mold growth.

RedGard vs Mortar Bed Liners

When it comes to mortar beds, you will hear a lot about PVC liners. That’s because these are the main waterproofing membranes used to protect mortar beds.

When installing a mortar bed, experts recommend that PVC liners, which are plastic sheets, be placed between the top and bottom layers.

The purpose of the sheet is to waterproof the mortar bed and prevent water from seeping through to other materials such as wood.

In the making of a mortar bed, there must be drainage, a slope, and weep holes. The assumption is that water will pass through the grout and tiles, be directed by the slope to the drainage, and any excess water that the mortar bed may have absorbed will be drained through weep holes.

The PVC liner is beneath all these things, and it will ensure moisture doesn’t get past that.

The thing about RedGard is that it’s not a substitute for PVC liners in mortar beds. We aren’t saying that RedGard is ineffective.

But considering where PVC liners are installed, which is at the bottom of the mortar bed, they play a critical role in waterproofing a surface.

You can’t substitute PVC liners with RedGard. You can only use RedGard as an additional protection measure.

How to Apply RedGard Over Mortar Bed?

Now that you understand what RedGard can do to a mortar bed, you need to learn how to apply it correctly. But before we share a guide on how to do this.

You need to know how the RedGard membrane works. When used, this membrane bonds to the substrate.

It creates a molecular bond to the surface, preventing moisture and water from seeping through. As long as the membrane remains intact, RedGard will continue to waterproof and isolate cracks.

If you are interested in applying RedGard over a mortar bed, here is an overview of the procedure you should follow;

Step 1 – Gather Essential Materials

You will only need two things for this project. Some RedGard and a roller brush. The latter is more effective at painting over a mortar bed since it’s a flat surface. If you prefer another tool, you can also use a paint sprayer.

You also need to figure out how much RedGard you need. The manufacturers recommend one gallon of RedGard for every 20 to 25 square feet. PPEs are a must.

Step 2 – Application

Before applying RedGard, you should clean the surface of the mortar thoroughly. Since the mortar bed will have already been cured, you don’t have to worry about adding water to the surface. Once clean, dry it with a clean cloth.

The mortar bed must be dry before RedGard is applied. Dip the roller brush into the RedGard and start applying the contents to the surface of the mortar bed. Ensure that every part is covered with RedGard. Give it two hours to dry.

Step 3 – Paint the Final Coat

Earlier, we mentioned that the manufacturers of RedGard recommend that you should apply two coats for this membrane to be effective.

For the second coat, you must apply it thinly. If you go too thick, there is a considerable chance that the bottom layer will fail.

Give it time to dry, and then you can install tiles over it.

Can You Tile Directly Over RedGard on a Mortar Bed?

One of the benefits of using RedGard instead of PVC liner is that you can tile directly over it. With PVC liner, you will have to add more mortar to the surface.

But with RedGard over a mortar bed, you can install tiles directly without needing more mortar. When you have a waterproof membrane such as RedGard over a mortar bed, you don’t have to worry about tiles not adhering.

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