You could end up using some cement board whether you plan to install new tile floors, shower enclosures, or tile countertops.


Although the Hardie board isn’t technically waterproof, it’s resistant to water damage. It can get wet since it absorbs moisture efficiently, but it has exceptional drying capabilities and will not deteriorate when exposed to water.

In this article, you’ll be reading about its properties, whether or not you should consider waterproofing it, and a step-by-step tutorial to guide you through the process.

Is Hardie Board Waterproof?

No, Hardie boards are not waterproof. But it is durable enough to be water-resistant, which means it efficiently absorbs water and holds up well against exposure to moisture.

However, some products are specifically designed to be waterproof, such as the HardieBacker 500 Waterproof Cement Board, which is made to be exposed to more water.

Although these boards could absorb water, they will not deteriorate due to moisture. The major reason cement boards aren’t watertight is the substrate on which they’re installed, not the boards themselves.

Don’t Confuse Water-Resistant With Waterproof Cement Boards

It’s a common misconception that Hardie boards are the best material for use inside a shower or tub area because many people are confused about the terms. You certainly can, but it is not always worth the extra cost and effort because it is extremely heavy.

Common water-resistant gypsum board is still the most suitable wall sheathing in a tub or shower room. It repels water because it is coated with a waxy substrate, yet it is about as strong as regular drywall.

Water-resistant is defined as a material that can withstand water penetration to a certain extent, but not completely. The term waterproof means the object is theoretically impenetrable to water, regardless of how long it is immersed or exposed to moisture or water.

Should You Waterproof Your Hardie Board?

Although most modern backer boards are moderately water-resistant and won’t break apart when exposed to water, they aren’t waterproof. On porous materials, you could use a barrier or sealer to prevent moisture from leaking through to the wood or metal studs underlying the tile.

The strength of a concrete backer board vs. a water-resistant gypsum board is the difference between the two. A concrete backer-board will most likely be your best choice if you’re seeking strength and longevity. 

To shield the wood studs from moisture, you should first place a watertight seal against the wood studs before placing the concrete backer-board.

With cement board, a vapor barrier is still required. However, you can hide the barrier beneath the board. The dampness will not be a problem because the cement board is hefty and breathable. Moisture cannot penetrate deeper into the wall if the vapor barrier is placed beneath the cement board.

Ceramic tile and grout are not waterproof in and of themselves, contrary to common perception. Water can seep into the substrate and make its way through the cement-based grout. Install a waterproof membrane near the tile as feasible just below the tile bonding mortar to prevent water damage.

How To Make Hardie Board Waterproof?

Below is a tutorial to help you make your Hardie boards waterproof. But before you start, here’s what you need:

  • Sealant
  • Paintbrush
  • Putty Knife
  • Liquid Membrane
  • Membrane Fabric

1. Sealing The Gaps

Use painter’s tape to protect your tub from excess substances like silicone and other waterproofing. Once these areas are covered, you can now use silicone to fill in the gaps between the tub and the cement board or Hardie board, then allow it to dry before you move on to the next step.

2. Apply The Liquid Membrane

Get a brush and slightly dip it into the bucket of liquid membrane and paint over the seams of the cement board with a moderately thick layer. Use a roll-up membrane fabric to ensure that you don’t leave any wrinkles or air bubbles. 

After applying the membrane fabric, you will need to apply another coat of liquid membrane. When applying the fabric to corners, you could use a putty knife or something similar to ensure that membrane fabric is stuck tight to the corner. Remember to exert moderate pressure. You don’t want to tear the fabric. 

Next, you want to apply the membrane around the top and front edge of the tub. Be sure to overlap the tub flange. Then apply the fabric to this area as well. After the first coat has finished drying, you can work your way to do another layer of liquid membrane.

3. Repeat The Process

It may be time-consuming, but you want to repeat this whole process to get the best results. You don’t need to cover the whole surface area of the board with the liquid membrane, but most people do this to get the best results. Besides, the liquid membrane doesn’t last very well on the shelf. 

Can You Tile Directly On Cement Board?

A cement board is a durable, sturdy foundation for tile. Unlike drywall, green board, or plywood, it does not contain any organic components, making it immune to mold, rot, shrinkage, or decomposition caused by moisture. 

Ceramic tile laid over cement board is one of the most long-lasting and resilient floor or wall surfaces you can install.

Hardie Board Is An Excellent Material If Properly Used

Even though Hardie Board isn’t waterproof, it remains a feasible solution for applications where moisture and water are mostly present. Getting a successful backer or dry partition requires a little more attention and treatment. If you’re having difficulty, remember to consult a professional.

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Matt Greenfield

Matt Greenfield is an experienced writer specializing in home improvement topics. He has a passion for educating and empowering homeowners to make informed decisions about their properties. Matt's writing focuses on a range of topics, including windows, flooring, HVAC, and construction materials. With a background in construction and home renovation, Matt is well-versed in the latest trends and techniques in the industry. His articles offer practical advice and expert insights that help readers tackle their home improvement projects with confidence. Whether you're a DIY enthusiast or a seasoned professional, Matt's writing is sure to provide valuable guidance and inspiration.

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