Kerdi Board vs. Cement Board: Which to Choose?

Kerdi Board vs. Cement Board: Which to Choose?

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If you are planning to do something in relation to tile underlayment, then you need to make sure you choose the right material, as you can’t just put tile down as is. Two popular materials for tile underlayment include cement board and Kerdi board.

They both share the same purposes on occasion, but they’re not at all the same things. Let’s figure out what both of these materials are, what makes them different, and which one to use for specific applications.

Kerdi Board and Cement Board: The Basics

Before we start talking about the similarities and differences between Kerdi board and cement board, let’s first figure out what they both are.

What Is Kerdi Board?

What is very interesting to note is that Kerdi board was actually created as a way to help mitigate the flaws that cement board has. Kerdi board is a multifunctional tile substrate and building panel. It is often used for tile underlayment and can be used with bonded waterproofing assemblies.

Simply put, it’s used to underlay tiles for both floors and walls. However, it can also be used in showers, bathtub surrounds, vanities, shelving, countertops, and more.

Kerdi board is made out of extruded polystyrene foam that features a special reinforcement material on both sides, as well as fleece webbing in the interior, which therefore allows for effective anchoring in thin-set mortar, as well as other kinds.

One of the biggest advantages that you get with Kerdi board is that it is extremely lightweight and, therefore, easy to work with and install.

Moreover, this material is also waterproof. It can handle exposure to a whole lot of moisture, which is obviously perfect for things like bathrooms and kitchens. Many people also use it as a waterproof barrier for other applications.

What is also neat about Kerdi board is that it has lines drawn on it that allow you to make easy cuts and measurements.

What Is Cement Board?

Cement board is another material that is generally used to underlay tile, usually in kitchens and bathrooms, as well as under normal floors. Cement board is an extremely inexpensive underlayment option, which is one reason many people may consider it, along with its long history of use. Durock, which you may have heard of before, is one of the most popular brands of cement board out there.

Cement board is made by mixing Portland cement, water, and reinforcement mesh, which is in the middle. The cement is poured over the mesh, allowed to dry and cure, and then forms a solid panel.

When using cement board, you first apply thin-set mortar to a wall, then cement board, then another layer of thin-set mortar, and then tile, with the idea being that the tile has a durable and hard surface to hang onto. That said, cement board can be extremely heavy, which is why many people have started using Kerdi board as a replacement.

What is also interesting to note is that, although this material is often used for underlayment for tiles in kitchens and bathrooms, it’s actually not 100% waterproof. Yes, it can handle a bit of moisture, but not all that much. Moreover, while hanging up pieces of cement board is not too difficult, if you need to cut it, things could get messy.

Similarities of Kerdi Board and Cement Board

Now that we know what both of these materials are, let’s figure out what makes them similar.

1. They Can Come in Various Sizes

Although not a huge similarity, both of these tile underlayment boards can come in various sizes to suit a variety of needs and spatial requirements.

2. They Can Serve the Same Purposes

Of course, the main purpose of both cement board and Kerdi board is to function as a tile underlayment.

Now, both are commonly used in kitchens, bathrooms, and for regular tile floor underlayment, although Kerdi board has become more popular as the years have gone on, which is due to the many advantages it has over cement board.

Differences Between Kerdi Board and Cement Board

Now that we are familiar with the similarities, let’s determine what makes these two options different.

1. Weight

One of the main differences between cement board and Kerdi board is that Kerdi board is much lighter, and therefore usually much easier to work with. Your average piece of cement board that comes in at 3’ x 5’ and 1/2” thick is going to weigh up to 60 pounds. Kerdi board, on the other hand, is going to weigh about 1/3 as much, if not less. You can easily pick up several pieces of Kerdi board at once, which you certainly can’t do with cement board.

2. Ease of Cutting

Something else to keep in mind is that cement board is quite difficult to cut, as you do need a circular saw with a masonry blade, plus it makes a whole lot of dust and mess when cut. Kerdi board on the other hand comes with lines pre-drawn on it and doesn’t require any special tools for cutting.

3. Ease of Installation

Due to the fact that it’s so much lighter, Kerdi board is generally much easier to install. A single person can easily install Kerdi board, whereas it’s usually going to take two people to install cement board. If cement board isn’t properly applied to a wall underneath, it can fall off due to its weight.

4. Waterproofing

Although cement board is popular and is often used as underlayment for tile with kitchen and bathroom floors, it’s not actually 100% waterproof, not even close. Yes, it can handle a bit of moisture, but not all that much. Kerdi board on the other hand, although not quite 100% waterproof, is much more water resistant than cement board. It, therefore, makes for a much better option to use in bathrooms and kitchens.

5. Fire Resistance

One thing that does stand out about cement board is the fact that it’s far more resistant to fire and combustion than Kerdi board is.

6. Overall Durability

Although the difference here is not huge, the fact of the matter is that cement board is a little bit more durable than Kerdi board. Therefore, if you are underlaying a tile floor in a high traffic area where many people will be walking, cement board may be the better option. Although cement board may still crack with a super heavy impact, it is still more resilient than Kerdi board.

7. Cost

One of the reasons cement board does remain a very popular option is due to its cost effectiveness. Generally speaking, you can expect Kerdi board to cost roughly twice as much as cement board. Your average piece of Kerdi board is going to cost you up to $40 (or more), whereas an average piece of cement board is usually going to cost $15, maybe $20 at most.

8. Composition

There is of course also the fact that cement board is made out of cement with a mesh lining in the middle, whereas Kerdi board is made mainly out of polystyrene. One is made out of cement, and the other is a durable type of foam with reinforcement.

Can Kerdi Board Be Used Instead of Cement Board?

Yes, you can absolutely use Kerdi board instead of cement board, and in fact, it is becoming a more popular option as the years go on. Sure, it might be more expensive, but it’s also much lighter, easier to install, and significantly more waterproof.

The only place where you may not want to use Kerdi board is if you have a tile floor that sees a whole lot of foot traffic, as cement board is a bit more durable and impact resistant.

Kerdi Board vs. Cement Board: Which of the Two Should You Use?

If you are underlaying a tile floor or wall in a kitchen or bathroom, particularly in any area that is going to see a lot of moisture, then Kerdi board is the much better of the two. However, when it comes to regular floors, such as in a living room, cement board is probably still the better option due to its higher level of durability.

You might also want to consider other cement board alternatives and Kerdi Board alternatives before settling for either of the two materials discussed here.


As you can see, both of these tile underlayment materials have both their pros and cons. Which one you choose really depends on the exact circumstance at hand.

How Does Cement Board Compare with Other Materials?

You might also be interested in seeing how cement board compares with: