Cement Board Over Wood Deck (An In-Depth Guide)

There comes a time when a wood deck starts to show signs of wear. For instance, it may lose its vibrant color, or you may notice cracking, rotting, and splintering.

It’s normal for a wood deck to lose its structure after a few years. And you can either fix it or give it a complete makeover by covering it with something else, such as a cement board.

This article will guide you on how to install cement board over a wood deck and everything else you need to know about this project.

Wood deck

Why Should You Install Cement Board Over Wood Deck?

The only reason why a person may be interested in installing a cement board over a wood deck is that you want to install tiles.

If your current wood deck is worn out, and you would like to have another material on your floor, tile is an excellent alternative.

You are probably wondering, what’s the role of the cement board in this scenario? If you have some tiling experience, then you know that wood isn’t suitable for tiles.

There is a high risk of failure involved when you lay tile directly on the wood deck. A cement board creates a stable surface for laying tile over a wood deck. Apart from the stability, cement board adheres more strongly to tiles than wood.

Instead of removing the worn-out wood deck, which is expensive and time-consuming, a cement board allows you to install tiles by covering the wood substrate below.

How Do You Install Cement Board Over Wood Deck?

Now that you know the role cement board plays in this project, let’s go through a quick guide on how you can install it over a wood deck.

Step 1: Assess the Condition of the Wood Deck

Even though installing cement board over a wood deck allows you to restore the beauty of your floor, you must examine its current condition.

Cement board should be installed on a structurally sound wood deck. That is why you need to inspect if the wood is in good condition.

If you discover the wood deck is stained or discolored, you can start laying cement board directly.

But if there are some signs of decay and rot, you will need to replace the affected parts before laying the cement board. Also, if the wood deck is disintegrating or too soft, it won’t hold up when the cement board is installed.

Step 2: Screw the Cement Board to the Wood Deck

Having confirmed that the wood deck is in perfect condition, you can proceed to fit the cement board. Measure the entire surface of the wood deck and cut it so it fits perfectly.

Fit the cement board to the wood deck and fasten the two materials using corrosion-resistant nails or screws.

Step 3: Cover the Cement Board with a Waterproof Membrane Before Tiling

You can tile directly over cement board, but in this step, I would advise you to apply a waterproofing membrane such as Schluter Ditra or RedGard. Cement boards allow water to pass through.

Therefore, without a waterproof membrane, the water that passes through the cement board can reach the wood deck and accelerate rot.

That is why you need to cover the two layers with a waterproof membrane. Then you can install tiles over it, and you will have successfully covered your worn-out wood deck with a more appealing finish.

Should I Use Thinset Mortar to Attach Cement Board to Wood Deck?

The best way to install cement board over a wood deck is by fastening the two materials with stainless steel nails or screws. Thinset mortar is not necessary.

Some contractors may use both nails and thinset mortar, but it’s not mandatory because as long as the surface is flat and structurally sound, you can easily attach cement board to a wood deck.

Don’t forget that wood easily sucks moisture from its environment. Using thinset mortar over a wood deck may suck out the moisture and affect adhesion.

So, the best solution is to nail or screw cement board over the wood deck. You can use thinset mortar to adhere tiles to the cement board.

Can You Install Tiles Directly Over Wood Deck Without a Cement Board?

Yes, you can. But it’s not advisable. Over the years, some contractors have successfully installed tiles on wood, which has held up for a long time. But this is more of a gamble.

Wood is highly susceptible to flexing. When exposed to moisture, wood tends to swell, and tiles can’t last on a surface that moves a lot.

A cement board creates a stable surface for you to tile over. Cement boards are pretty sturdy and prevent movement in the wood beneath from reaching the tiles.

Therefore, as tempting as it may be to skip the cement board and tile directly over a wood deck, you should refrain from doing so.

Do You Need to Use Plywood Between the Wood Deck and Cement Board?

If the wood deck is in perfect condition, you can skip the plywood and screw the cement board over the wood deck.

However, if you want to reinforce the structural strength between the cement board and the wood deck, you can use plywood as a transition material.

Whether you should use plywood in between these two materials heavily depends on the condition of the wood deck.

But to be safe, you can always screw plywood over the wood deck and then follow it up with cement board.

Do You Have to Tape the Joints of the Cement Board When Installing It Over Wood Deck?

When fitting cement board over the wood deck, there will be a couple of seams on the joints. Even if you are going to install a waterproofing product, it’s important to cover these seams using fiberglass mesh tape.

Get some as you are buying the cement board. Cut and apply it on the seams. It’s okay to overlap on both sides. Then cover the tape with thinset mortar. You will now have waterproof seams.

Is It Advisable to Drill Drainage Holes on Cement Board Over Wood Deck?

Many homeowners with a wooden deck like drilling drain holes to help prevent water from remaining stagnant in one area.

However, this is not advisable. Because when you drill drain holes, they will leave the wooden deck exposed to water, and it may start to rot. Drilling drain holes negates the importance of installing a waterproofing product.

The best way to deal with stagnant water on your cement board and wood deck is by creating a slope or using other methods, such as erecting a shade.

Tampering with the structure is not advisable as it makes the wood more vulnerable to water damage.

Cement board

Should You Install Cement Board Over a Squeaky Wood Deck?

If your wood deck is squeaking, then it means that the structure is weak. Therefore, you should not install a cement board over it.

A squeaky wood deck can easily be fixed by screwing down some plywood deeper into the floor joists. Alternatively, you can identify worn-out pieces of wood and replace them with newer ones.

Is There a Wood Deck Made Out of Cement?

In your quest to resurface an old wood deck with cement board, you may come across a product known as fiber cement decking. Even though wood decks look amazing, they are usually more vulnerable to water damage and wear.

Fiber cement decking comprises Portland cement, cellulose fibers, and glass. This material doesn’t absorb moisture, and neither does it rot or swell.

Fiber cement decking doesn’t fade easily, and even if it does, you can easily repaint it. It’s available in plenty of finishes that resemble real wood.

For now, you can refinish your wood deck with cement board and tile. But in the future, you should consider fiber cement decking because it’s much stronger and more durable than its wooden counterpart.

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