When and How To Use Cement Backerboard for a Durable and Reliable Base

Any time you’re working with tile or brick, there’s a good chance you’ll need cement backerboard. This durable material provides a more stable base and better water resistance than standard drywall, making it ideal for kitchens and bathrooms. In this guide, we’ll walk through exactly what cement backerboard is, when to use it, and how to install it.

What Is Cement Backerboard?

Cement backerboard consists of a thin layer of concrete sandwiched between two layers of fiberglass. This composition gives the material its strength and water-resistant properties. You may hear people refer to it by several names, many of which are brand names. It’s often called Durock, Hardie Board, HardieBacker, or simply cement board.

While not completely waterproof, cement backerboard is unaffected by water and doesn’t deteriorate when exposed to moisture like drywall does. Unlike wood-based products, cement backerboard resists mold growth and rot. It can be installed over drywall, attached directly to studs, or placed on top of a subfloor.

Typically available in ½-inch or ¼-inch thicknesses, cement backerboard comes in sheets measuring 3 feet wide by 5 feet long, though larger 4-foot by 8-foot sheets are also available. The ½-inch variant is most suitable for flooring, while ¼-inch is ideal for walls. 

Common Uses for Cement Backerboard

Cement backerboard serves various purposes in construction and renovation projects. Its versatility makes it a go-to material for many professionals and DIY enthusiasts alike.

One of the most common uses for cement backerboard is as a substrate for tile installations. The stable and level surface it provides creates a stronger bond with tile adhesives than materials like plywood. This makes it an excellent choice for both floor and wall tile installations and tile countertops.

Due to its water-resistant properties, cement backerboard is ideal for use in areas prone to moisture exposure:

• Bathroom walls, floors, and ceilings
• Shower surrounds
• Laundry rooms
• Kitchen backsplashes

While cement backerboard itself is water-resistant, a vapor barrier should still be installed behind it in these applications to protect the framing.

Exterior Applications

Since cement backerboard is durable, weather-resistant, and can support extra weight, it’s also a good choice for various exterior projects, such as:

• Brick or stone veneer installations
• Masonry skim coats
• Stucco applications
• Outdoor kitchen constructions
• Mailbox columns and similar structures

When To Use Cement Backerboard vs. Alternatives

While cement backerboard is an excellent choice for many projects, it’s not always necessary or the best option. Understanding when to use it and when to opt for alternatives can help you make informed decisions for your projects.

Cement Backerboard vs. Drywall

Cement backerboard is more moisture-resistant and durable than drywall, but it’s not always necessary. Drywall is a better choice in the following scenarios:

• The wall won’t be tiled or exposed to moisture
• A smooth surface is needed for painting or wallpapering
• Weight is a concern, as cement backerboard is heavier than drywall

Cement Backerboard vs. Plywood

While plywood is commonly used as a subfloor, cement backerboard provides a more stable surface for tile installations and has better moisture resistance for wet areas like bathrooms and kitchens. However, plywood may be preferred when:

• A more flexible substrate is needed
• The project requires a lighter material
• Cost is a primary concern, as plywood is generally less expensive

How To Install Cement Backerboard

The following steps will explain how to install cement backerboard over a subfloor for a floor tile installation. The steps are largely the same for walls, but applying thinset for wall installation is typically not necessary.

Tools and Materials Needed

• ½-inch cement backerboard
• ¼-inch notched trowel
• Cement board screws
• Heavy-duty carpenter’s pencil or permanent marker
• Jigsaw
• Measuring tape
• Mesh drywall tape
• Putty knife
• Screwgun
• Thinset (premixed is easiest)
• Utility knife

Step-by-Step Installation Guide

1. Remove any existing flooring until the plywood or tongue-and-groove subfloor is exposed. If the floor requires repairs or any sections of the subfloor need to be screwed back down, do so now.
2. Dry-fit a few sheets of backerboard at a time. When you lay them in place, position them so the backerboard seams don’t line up with the existing plywood subfloor seams and make sure to also stagger joints for each row. Leave a ⅛-inch gap between the sheets and a ¼- to ⅜-inch gap between the edges of the sheets and the wall.
3. Before making any cuts, measure and mark the concrete backerboard. Use a utility knife to cut the fiberglass mesh at the mark, and then cut through the rest with a jigsaw at the marked line. Test-fit the piece to ensure it fits well and remove the sheet of cement backerboard.
4. Working one sheet at a time, apply thinset to the floor. Spread it out with the flat side of the trowel and then create ridges with the notched side.
5. Lay the cement backerboard down onto the wet thinset. Wiggle it back and forth until it fits properly in the space, maintaining a ¼-inch gap between the edge of the sheet and the walls.
6. Fasten the cement backerboard in place by driving cement board screws through the cement backerboard and into the subfloor below. Starting about an inch in from the edges, drive a screw every 8 inches. Be sure to continue driving the screw until the head of the screw is slightly below the surface of the cement backerboard, similar to how you would install drywall. Move on to the next piece of cement backerboard.
7. Once the entire floor has been covered in cement backerboard and fastened into place, it’s time to tape the seams between the boards. Note: Do not tape the seam between the edges of the cement backerboard and the wall.
8. Starting one seam at a time, use the putty knife to apply a 3- to 4-inch-wide bead of thinset across the joint. Apply the tape over the thinset and push it in with the putty knife before smoothing out any lumps, high spots, or gaps. Tape the rest of the seams in the same fashion.
9. Allow the thinset to dry for a few days before you begin tiling. The thinset underneath the cement board won’t breathe well, so it will take some time to dry.

Tips for a Successful Backerboard Installation

Always wear protective gear, including safety glasses and a dust mask. Wear heavy-duty gloves to protect your hands when handling the material, and use knee pads if working on floor installations to prevent strain and injury. Make sure you have proper ventilation when cutting cement board to minimize the amount of dust you inhale.

Use a carbide-tipped scoring tool for cleaner cuts in the cement board, and double-check measurements before cutting to avoid waste and errors. Apply even pressure when driving screws to prevent damaging the backerboard surface.

Repair Tips

If you notice cracks or damage in the cement backerboard, repair them promptly to prevent further deterioration. Small cracks can be filled with thinset mortar, while larger damage may require patching or replacing sections of the backerboard. Always follow manufacturer guidelines for repairs to ensure the best results.