Tools and Materials
Tools
- Utility Knife
- T-Square or Adjustable Square
- Hammer
- Drill/Driver
- Screwdriver Bits
- Screwdriver
- 1/4-in Notched Trowel
- Shop Vacuum
- Shop Vacuum HEPA Filter
- Clamps
- Safety Glasses
- N95 Respirator
- Work Gloves
- Hearing Protection
Rasp
- Circular Saw (Optional)
Four- or Six-Tooth Fiber-Cement Circular Saw Blade (Optional)
- Carbide-Tipped Hole Saw (Optional)
Product costs, availability and item numbers may vary online or by market.
How to Cut Cement Backer Board
You can cut cement backer board and fiber cement board using different methods, depending on the cuts you need to make. We have general steps for how to cut backer board below but always follow the cutting instructions for your board type.
Cutting and breaking cement backer boards can release silica dust. Follow the board manufacturer’s precautions and instructions. When cutting cement boards, make sure your workspace has good ventilation. Wear safety glasses, an N95 respirator, work gloves, and, if using power tools, hearing protection.
Cut Cement Boards With a Utility Knife
You can cut cement boards easily with just a straight edge and a utility knife
Step 1: Prepare to Cut the Cement Board
Step 2: Score the Cement Board
Hold the square in place and run a utility knife along the edge at the cut line to cut through the mesh reinforcement. Score the cut line several times for the best result. Have spare utility knife blades ready. Cutting cement board dulls standard blades quickly. As an alternative, you can use a carbide-tipped scoring tool instead of a utility knife.
Step 3: Snap the Board
Remove the square, support one end of the board, and snap the board at the score line. Cut through the mesh on the other face of the board and smooth the edges with a rasp if necessary.
Cut Cement Boards With a Power Saw
You can use a circular saw to cut cement board outdoors with the right blade and procedure. Follow the instructions for your board, but here are general steps.
Step 1: Put on Safety Gear
Work outside, and connect the saw to a dust collection system to control the silica dust. Wear your safety gear.
Step 2: Cut the Cement Board
Install a four- or six-tooth, diamond- or carbide-tipped blade designed for cutting fiber cement on your saw. Set up a saw guide to help you make a straight cut. Clamp and cut the board to size. Follow the saw and blade manufacturers’ instructions for use and safety.
Make Circular Cutouts in Cement Board
You can use a carbide-tipped hole saw and power drill to make circular cuts in cement backer board for pipes, valves, conduit or cable. Work outside and clamp the board to a stable surface.
Use a shop vacuum with a HEPA filter (high-efficiency particulate air filter) to vacuum up silica dust. Wear eye protection and your respirator. Dispose of the dust and scrap pieces of cement board according to the guidelines for your area.
How to Install Cement Board
These steps on how to install backer board give you general instructions for installing cement boards for a tile floor and for tiling a wall. Follow the instructions specific to your board and project and follow all building codes for your area.
Make sure the installation area has good ventilation. Turn off power to any nearby outlets, switches and light fixtures.
Install Cement Board for a Tile Floor
Before installing backer board for a tile floor, check the subfloor to ensure it’s clean, free of dust and in good shape. Apply leveling compound if necessary. Remove and replace any warped or damaged sections. Check the backer board manufacturer’s instructions to ensure your subfloor is suitable for the board.
Step 1: Dry Fit the Backer Board
Dry fit (lay out without adhesive) cement boards, staggering the joints and ensuring they don’t line up with the subfloor joints. Use 1/8-inch tile spacers to create a gap between the board edges and between the boards and the walls . Cut the boards to fit.
Step 2: Spread Mortar and Place the Boards
Take up the boards and begin applying polymer-modified thinset mortar to the subfloor with a 1/4-inch notched trowel. Apply just enough for the first board. Comb the mortar and then press the cement board into the mortar to fully engage it. Repeat this step for the remaining boards. Use the spacers to maintain the 1/8-inch joints and spacing from the walls. Remember to stagger the board joints and make sure they don’t line up with the subfloor joints.
Step 3: Install the Cement Boards
Fasten the cement boards to the subfloor with the cement board screws or hot-dipped galvanized roofing nails every 8 inches on center (from the center of one screw to the center of the next). Drive the screw heads flush to the surface. Keep the screws 3/8 to 3/4 of an inch from the board edges and 2 inches from the corners.
Step 4: Tape the Board Joints
Remove the spacers and apply the thinset to the joints. Feather it out to about 1-1/2 inches on each side. Press 2-inch alkali-resistant fiberglass tape into the mortar to strengthen the joints. Spread thinset over the tape, feathering the material along the edges to create a smooth surface.
Once you have a sturdy backer board base, you’re ready to install your tile floor. Don’t have time to do it yourself? See how Lowe’s can help with professional floor tile installation. We’ve also got tips for choosing floor tile for your bathroom.
Install Cement Board for Tile Walls
Before installing cement boards for wall tile, make sure the studs are structurally sound and plumb, with no high spots. You’ll either need a vapor barrier behind the cement board or for wet areas like showers and tubs, a waterproofing membrane over the boards. Use only one method, depending on your project.
Step 1: Prepare for Installation
Plan your layout and cut cement boards to fit. Use 1/4-inch spacers to create a gap between the board edge and the floor, tub or shower.
Step 2: Fasten the Cement Boards to the Walls
Align a board with a wall stud , leaving space on the stud for adjacent boards. Maintain the 1/4-inch gap at the floor, tub or shower. Secure the boards with cement board screws or hot-dipped galvanized roofing nails every 8 inches on center. Keep them 3/8 of an inch from the board edge and 2 inches from the corners. Drive the heads flush with the surface of the board. Install the remaining boards. Installers typically leave a 1/8-inch joint between the boards but check your instructions for any specific spacing.
Step 3: Fill and Tape the Joints
Spread polymer-modified thinset mortar into the joints and extend it about 1-1/2 inches on both sides. Press 2-inch alkali-resistant fiberglass tape into the mortar and spread thinset over the tape. Smooth and feather it out a couple of inches on each side.
Waterproofing requirements vary depending on the product and local codes, so follow the instructions for your boards and the codes for your area.
Step 4: Apply Waterproofing, if Necessary
Waterproofing requirements vary. If you’re installing standard cement board in a shower, tub or other wet area, or if specified by the manufacturer or by code, apply a waterproofing membrane according to the manufacturer’s instructions.
See our ideas for shower tile designs and get steps for installing tile for a shower wall.
Cutting and Installing Cement Backer Board: Key Points
Cutting and installing cement board the right way prepares your floors and walls for a strong, beautiful tile installation. Remember these key points when you work with cement backer board:
- Wear eye protection, an N95 mask and, if using power tools, hearing protection.
- Use a straight edge and utility knife to score and cut cement board indoors.
- Work outdoors if you use a power saw or a hole saw to cut cement board.
- For floors, apply thinset mortar to the subfloor and secure the boards with cement board screws, leaving 1/8-inch gaps next to walls and between boards.
- For walls, secure the cement boards to studs, with a 1/4-inch gap to the floor, shower pan or tub, and a 1/8-inch gap between boards.
- Wall installations need either a vapor barrier behind the boards or a waterproofing membrane on the face of the boards, depending on the product, project and building codes.
Shop Lowes.com for the cement board you need to tile a floor or shower and the tools you need to cut and install the backer board. We’ve also got mortar, cement board screws and waterproofing for your project. If you’re not sure what you need, stop by your local Lowe’s. A Lowe’s Red Vest associate will help you find all the materials and tools you need for a beautiful tile job.
FAQ on Cutting and Installing Cement Backer Board
Use the answers to these common questions to plan your cement board installation.
What’s the Best Way to Cut Cement Board?
The best way to cut cement board is with a straight edge and a utility knife. Score the board through the mesh material and then snap the board at the score line. This simple method can be done indoors, requires just a couple of basic tools, and produces a minimal amount of dust. Protect yourself with safety glasses and an N95 respirator.
How Do I Reduce Dust When Cutting Cement Board?
Scoring and cutting cement board with a utility knife creates less dust than using a power saw. If you cut cement board with a power saw, cut it outdoors. Connecting the saw to a dust collection system is a good idea. Wear eye protection and an N95 respirator whenever cutting cement board. Wear hearing protection when using a power saw.
Do Drywall Screws Work for Cement Board Installation?
No, install cement board with corrosion-resistant cement board screws. Alkali in the cement boards will cause drywall screws to corrode, weakening the board as well as the tile installation.
Should I Apply Waterproofing to Cement Board for Wet Areas?
You usually need to apply waterproofing to cement board for showers, tubs and other wet areas before you install tile. Waterproofing might be necessary for other applications, depending on the product, project and building codes.