Backer Board: The Ultimate Guide

If you’ve ever tackled a tiling project, you’ve likely heard of cement backer board. It’s like the trusty sidekick of tiles—always there, silently doing its job so the main star (your beautiful tiles) can shine. But what exactly is it, and why should you care?

Let’s break down the nitty-gritty of backer board, explore installation techniques, and help you make informed decisions on the best product for your next big project. You ready?

What is Backer Board?

Backer board, sometimes called cement board, is a construction material used as a sub-surface for tiling projects. Backer board is a combination of cement and reinforcing fibers formed into sheets (usually 3’x5’ and 4’x8’) of varying thickness. It provides a solid, moisture-resistant surface, ensuring your tiles don’t end up popping off or becoming uneven.

Think of it as the unsung hero that helps you achieve that flawless tiled look in your bathrooms, kitchens, and beyond. If it’s installed properly (we’ll discuss that in a bit) you’ll never see it and your tile will last a very long time.

For smaller tile projects like mosaic tiles, and especially on older houses, backer board is uber important. Without it you get uneven tiles that move and crack as your house moves. Don’t skip this imperative product.

Strengths

1. Water Resistance: Cement backer boards are highly resistant to moisture, making them perfect for wet areas like bathrooms and kitchens. After all they’re made of cement.
2. Durability: They provide a sturdy foundation, preventing tiles from cracking or shifting over time.
3. Versatility: Suitable for floors, walls, and countertops, they can be used in various tiling projects.
4. Easy to Cut: Despite their toughness, they can be easily cut to fit any shape or size needed for your project.

Weaknesses

1. Weight: Cement backer boards can be heavy, making installation a bit of a workout.
2. Dust: Cutting them generates a lot of dust, which can be messy and a health hazard if inhaled. A mask is your best friend here.
3. Price: They can be more expensive than other underlayment options, like drywall.

What Thickness Backer Board Do You Need?

The thickness of cement backer board you choose is crucial to the success of your tiling project. Different applications call for different thicknesses.

A big thing to consider when choosing a thickness is what the finished floor height should be. Ideally, you want a tile installation to be flush with any flooring it intersects with to avoid the need for reducers or other unattractive transitions. This also eliminates trip hazards.

1/4-inch Thickness

Best for: Floor tiling over existing subfloors.

• Use it when: You need a stable underlayment that doesn’t significantly raise the height of your flooring. Ideal for installations over plywood subfloors.
• Pros: Lightweight and easy to install, suitable for most floor tiling projects where height considerations are a factor.
• Cons: Not recommended for wall installations due to insufficient structural support.

1/2-inch Thickness

Best for: Walls, countertops, and floors where added strength or height is needed.

• Use it when: You’re installing tiles on walls or need extra durability on floors. This thickness is standard for most vertical applications and where tiles need strong backing. The 1/2” thickness lines up almost perfectly with drywall which makes this a great choice for shower surrounds.
• Pros: Provides better support and stability, especially in high-moisture environments like showers.
• Cons: Heavier and can add more height to the flooring, which might require adjustments to transitions between rooms.

5/8-inch Thickness

Best for: Heavy-duty flooring and industrial applications.

• Use it when: You’re dealing with areas that require extra strength and support, such as commercial kitchens or high-traffic areas. A great option to match commercial drywall thicknesses of 5/8”
• Pros: Offers the highest durability and resistance to bending or flexing under heavy loads.
• Cons: Heaviest and most challenging to install, requiring more effort and skill.

Installation Techniques and Best Practices

Installing cement backer board is relatively straightforward, but it’s essential to do it right to ensure the longevity of your tiles. I just finished a subway tile bath surround using 1/2” backer board if you wanna check that out here. Here’s a quick guide:

1. Gather Your Tools: You’ll need a drill, backer board screws, a sharp utility knife, a trowel, and thin-set mortar.
2. Prepare the Surface: Make sure your surface is clean and dry. Remove any old adhesive or debris.
3. Cut the Backer Board: Measure and cut your backer board to fit the space. Use a utility knife or a circular saw with a carbide-tipped blade for larger cuts. Have extra blades if using a utility kniofe because they will dull quickly!
4. Apply Thin-set Mortar: Spread a layer of thin-set mortar on the surface using a trowel. This helps to bond the backer board to the subfloor or wall. More on this below.
5. Lay the Backer Board: Place the cut pieces of backer board onto the mortar. Leave a small gap (about 1/8 inch) between sheets for expansion.
6. Screw It Down: Secure the backer board with backer board screws, placing them every 6-8 inches. Make sure they’re flush with the board’s surface.
7. Seal the Joints: Use fiberglass tape and thin-set mortar to seal the joints between the sheets. This step is crucial to prevent moisture penetration.

Do I Have to Apply Thin-set First?

Go and ask this question on Reddit and see what happens? People will go straight nuts. Some tile setters will say they’ve done it for 20 years without thin-set and never had a problem and the rest of the internet thinks they’re insane.

The manufacturers all require that backer board be set into a layer of thin-set and then screwed down if you want them to honor their warranty. In my experience, I have done it both ways over 15 years and have not noticed a difference in performance between installing backer board in thin-set and skipping the step.

Best practice, yes. Do you want to live on the edge like me? Maybe. Maybe not.

What Screws Do I Need?

Each of the brands of backer board below have a very specific screw that is designed for use with their cement mix. Do I understand it fully? No. Is it possibly a marketing gimmick? Sure. Does it void your warranty if you use the wrong screws? Yes.

Bottom line pick the backer board you prefer and buy the screws that are designed for use with that backer board. The costs differences are negligible.

Now what types of backer board are available? Here’s are the three big ones you’ll be able to find almost anymore.

Durock Cement Board

Best for: Bathrooms and other high-moisture areas.

Pros: Known for its superior moisture resistance and durability. It’s also relatively lightweight compared to other cement boards.

Cons: Can be pricier, and cutting can be dusty.

Screws: Rock-On

HardieBacker Cement Board

Best for: Floors and countertops.

Pros: Easier to cut and install, with great water resistance. It’s also mold-resistant, which is a huge plus in wet areas. The grid pattern on this makes straight cuts so easy too.

Cons: Slightly heavier than other options, and like all cement boards, it can be dusty to work with.

Screws: Backer-On

WonderBoard Lite

Best for: Walls and ceilings.

Pros: Lightweight and easy to handle, making it ideal for vertical installations. I find this one to be by far the easiest to cut and handle.

Cons: While durable, it’s slightly less so compared to Durock and HardieBacker in high-traffic areas. Screws around the edges can blow out more easily.

Screws: Rock-On

Making the Right Choice

When choosing a cement backer board, consider the environment where it will be installed and the specific needs of your project. High-moisture areas will benefit from Durock’s water resistance, while HardieBacker’s ease of installation makes it ideal for DIY projects. For vertical applications, the lightweight WonderBoard Lite is a great choice.

Whatever you do don’t tile directly onto you drywall or plywood subfloor if the tile has any potential of getting wet. Plywood is too unstable and will break your tile with movement and drywall fails early and often when it gets wet.

If you’re installing on top of concrete floors then you don’t need any backer board because the cement is already there. Just make sure the floor is level and if you need to use some mortar or self-lever to accomplish that feel free, but skip the extra step of backer board.

Congratulations, you have just graduated from backer board university. Now go forth and tile like a pro!