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Can Cement Board Be Used Outside? Can It Get Wet?

Cement boards are used as the backing material for installing tile, stone, and brick. They are made of cement and cellulose containing plant fibers they are more porous.

But will cement boards work the same outside or will they get wet? Read ahead to find out more!

Can cement board be used outside?

Cement boards can be used outside. Contrary to popular belief, cement boards are made of materials that make them very durable and waterproof. Hence, cement boards are resistant to outdoor factors. As such, you can use them for the base of outdoor fixtures made with wood or steel.

Cement boards are used as a foundation for many outdoor fixtures. This is because the material they are made from makes cement boards ideal to be used outdoors.

Despite being made of plant fibers, cement boards do not have enough organic makeup. As such, there is no risk of fungi growth or mold. As this is a recurring problem, cement boards are a great solution.

In addition to that, cement boards are water-resistant. So you can use them if you live in an area with frequent rain or for structures with constant water exposure.

Can you use a cement board for the exterior wall?

Cement boards can be used for the exterior wall. Not only are they durable but cement boards add strength and impact resistance to the wall. 

Plus, cement boards are good at keeping moisture out. This means that any sort of water damage like mold and mildew buildup can be prevented.

How long does the cement board last outside?

How long the cement board will last will depend on two factors. Proper installation and maintenance.

On average, manufacturers and contractors will give you a 10 to 30 years guarantee. However, most cement boards have a lifespan of roughly 50 years.

To ensure that your boards last longer, it is wise to choose high-quality cement boards. Good quality cement boards will ensure that despite the weather condition, the board is able to last longer.

While cement boards are water-resistant, they are not 100 percent waterproof. High-quality cement boards will only let the least amount of water to pass, ensuring longevity.

What cement board can I use for an outdoor bbq?

We recommend using the PermaBASE cement board for an outdoor kitchen AND BBQ. Their cement boards are both moisture and mold-resistant. And are made to withstand moisture for indoor and outdoor fixtures.

If you are looking to make an outdoor kitchen or outdoor bbq, the cement board needs to be durable. On top of that, it also needs to be able to withstand moisture.

Cement boards are water-resistant, not waterproof. As such, when choosing a cement board for your outdoor bbq you need to select one that will be able to endure constant exposure to moisture. Because kitchens need a water outlet.

How to use cement board outside?

Using the cement board outside needs some set of rules to be followed. This set of rules ensure that the lifespan of the cement board is held upright. Let’s dig in deep to know more about them.

Prepare for a straight surface:

Tile is easier to set on a straight wall. It looks better on a straight wall as well. Remove any crooked studs or nails to straighten out the surface. You can replace the crooked studs with new straight ones for an even surface.

Add blocking to the surface:

You will need to add blocking to the screw in the cement boards. There should be backing for all the edges. 

Waterproof the surface:

Add plastic sheets to the framing to waterproof the surface. Make sure to staple in the sheets tightly.

Hang and screw in the cement boards:

Hang the cement boards to be sure about their placement. To avoid breakage, screw in the cement board 1 inch away from the edge. Do not drive the screws at an angle or break the mesh.

Seal the seams:

Seal the seams with fiberglass mesh tape and mortar dry.

Can cement board get wet?

Cement boards can get wet. They are water-resistant but not waterproof. However, cement boards have exceptional drying properties. As such, they will not be ruined or deteriorate when exposed to water. Instead, if they do get wet, you can let the cement board dry before installation.

Cement boards can get wet as well. They are made of cement and plant fibers, so cement boards are very durable and water-resistant. As it is water-resistant, not waterproof, there is always a chance for the cement boards to get wet.

However, exposure to water and moisture will not ruin or deteriorate cement boards. Cement boards last for about 50 years on average. So even if they do get wet, there will be no long-lasting damage.

You can simply wait for the cement board to dry in case it gets wet before you install them. Cement boards have excellent drying properties.

Can cement board get rained on?

Cement boards can get rained on and absorb moisture. As they have excellent drying properties there will be no lasting damage or deterioration.

However, you will need to ensure that the cement board is completely dry before you install them. Otherwise, there is a risk of breaking the cement board.

Is cement board waterproof or water-resistant? Does it need waterproofing?

Cement boards are water-resistant, not waterproof. This means that cement boards will not completely prevent water. And when you are exposed to water, they are more likely to absorb the moisture.

But cement boards have extraordinary drying properties. So even if the boards do get wet, they will dry out quickly without any damage to the board.

As cement boards are not waterproof, they will need waterproofing. This is especially needed if you are using the cement board for areas that have constant exposure to water.

This includes areas like the shower or bathroom and outdoor areas with frequent rain. 

What can I use to waterproof the cement board?

The easiest and fastest way to waterproof cement boards is by using a liquid membrane. They are a liquid-based coating that forms a rubber-like elastomeric texture once cured. Liquid membranes are also fully bonded and monolithic.

Liquid membranes are mostly used to prevent water from coming in contact with the material it is laid over. This means they waterproof the material.

You can directly apply the liquid membrane over the seams of the cement board using a spray or a brush. Liquid membranes can also be adhesive. So you can also use a roll-up membrane fabric for extra water protection.

How to waterproof cement board?

Using the waterproofing agent to waterproof the cement board can be done easily. Take a look below to make the process easier for you.

Apply a thick coat of liquid membrane:

Apply a coat of liquid membrane around the seams of the cement board. Make sure that the coat is thick so that it sticks better.

Apply membrane fabric on top:

Over the layer of liquid membrane, add a layer of roll-up membrane fabric. The membrane fabric will provide additional protection against water making it extra waterproof.

Cover the fabric with more liquid membrane:

Cover the fabric with more liquid membrane. Not only will the liquid membrane glue the fabric but seal it in place. So there is no risk of being misplaced.


Repeat this process for every seam for all the cement boards.

Apply liquid membrane all over:

Once the seams of the cement board are entirely coated, apply liquid membrane all over the boards. There is no need to add roll-up membrane fabric here. Wait for the liquid membrane to dry.

What can I cover the cement board with?

To finish installation, cover the cement board using fiberglass mesh tape. Apply the mesh tape over the seams, joints, and corners. Even the joins where the cement board and the drywall meet.

To seal in the fiberglass mesh tape, apply a thick layer of thin-set mortar. Make sure to squeeze the mortar through the tape to fill in the cracks.

To make the cement boards more aesthetically pleasing you can cover them with tiles or stucco. For outdoors, it is best not to cover the cement board with tiles or stucco. Instead, you can paint over the cement board. 

Do you need a vapor barrier behind the cement board?

Vapor barriers are used to prevent vapor from penetrating the cement board or the sub-surface. The need to install a vapor barrier depends on the climate of your area and the side of the building. 

Vapor barriers are a requirement for colder climates more so than warmer climates. In cold climates, vapor barriers are to be installed on the inner surface of the wall to stop vapor diffusion through the floors, walls, and roofs.

It is important to have a vapor barrier behind your cement board if you live in colder climates. This is to prevent any moisture problem from occurring, thus, preventing water damage.

Final Thoughts:

Cement boards can be used outside and get wet. Courtesy of their drying properties, cement boards can tackle climate changes like snow and rainfall very well. This makes them great materials to be used outside. There will be no changes to the quality of the board even if they do get wet.