Cement board provides a solid, waterproof base for laying tiles
Whether you’re installing a ceramic tile floor, tiling a kitchen backsplash, or building an entire tile shower, you need a solid base on which to create your masterpiece. Cement board is the premier construction material to make that happen. Better than a drywall or plywood substrate, cement board is almost as easy to install and provides a water-resistant, mold-free, and durable work surface. However, it’s made with concrete, so it can be difficult to cut. In this guide, we’ll explain how to cut cement board quickly and easily using a variety of tools.
Cement board is an underlayment material that most contractors use as a base for tile installation. It contains cement-like materials around a fiber mesh and is available in 3-by-5-foot or 4-by-8-foot sheets that are 1/4-inch to 1/2-inch thick. Cement board provides a solid, flat, water-resistant, and durable base layer for any tile project, inside or out. Cement board is superior to a drywall substrate in wet areas due to the cement board’s ability to avoid mold and mildew growth.
Cutting cement backer board requires special considerations beyond standard tool safety measures. Make sure you take the following safety precautions to keep yourself protected:
Ventilate the area: You’ll create a lot of unpleasant and dangerous dust when cutting cement boards. Work in a well-ventilated area or outside, if possible.
Wear a respirator: Cutting cement board releases airborne silica particles that can cause irreversible lung damage. Simple dust masks can’t filter silica dust. Wear a particle filtering respirator mask at all times while you work.
Wear safety goggles: The same dust you shouldn’t breathe in can also irritate your eyes. Opt to wear safety goggles that completely cover your eyes instead of simple safety glasses.
Wear work gloves: Protect your hands from the cement board’s sharp edges by wearing work gloves while cutting and handling the product.
Follow tool safety precautions: Many cuts in cement board require using power tools. Always follow the proper safety guidelines for the power tools you’re using.
You may be familiar with this cutting method if you know how to cut drywall. This method is best for use when making long, straight cuts in cement board, especially if you don’t have access to power tools.
Clear an area large enough for the cement board to lay flat with a couple of extra feet available on each side.
Lay the cement board flat on the cleared surface.
Measure, mark, and draw a line where you’ll cut.
Use a sharp utility knife to score the length of the line. Use a straight edge to get a perfect cut.
Score the same line two more times to create a groove.
Stand the cement board on its end with the scored line in a vertical position.
Position your knee at the scored line on the opposite side of the board.
Apply pulling force to both sides of the cut line until the cement board snaps and forms a V shape.
Using the utility knife, cut the mesh inside the V shape.
You’ll likely need to replace the blade several times during the project, as the cement and mesh will wear down the edge.
Using a utility knife to cut cement board is simple and straightforward, making it the ideal way to cut large sections of board without power tools. However, it’s not the best option in all circumstances.
If you’re installing a lot of backer board or have multiple rooms to tackle, investing in a circular saw will make the job go much faster. Additionally, since you score and snap with a utility knife, it’s not a suitable method for cutting corners or cut-outs. Use another method to cut around outlets, switches, and other areas.
To cut a straight line in cement board that doesn’t extend for the entire length of the material, you can outfit a circular saw with a rough-cutting, carbide-tipped, low-tooth-count, wood-cutting blade. A small number of teeth will create less dust than a blade with many teeth.
Place the cement board face down on a pair of sawhorses.
Measure, mark, and draw a straight line where you want to cut.
Set the depth of the blade to no more than a 1/2-inch deeper than the material.
Align the saw at the edge of the board, and use a T-square to maintain a perfectly straight cut.
Bring the saw to full speed.
Push the saw slowly and smoothly along the line.
Using a circular saw to cut cement board is ideal in most situations. Much like using a utility knife, you can use a circular saw to cut straight lines from one end of the board to the other. It makes quick work of the cuts, so it’s ideal for cutting full boards for a larger project.
Additionally, since you’re not scoring and snapping the board, you can make partial cuts through it, which means you can cut corners into the board. A circular saw isn’t useful for making cutouts for outlets, but if you need to cut a inside corner to fit around a cabinet or tub, you can cut two partial perpendicular lines and then snap the cutout out.
You can make quick work of cutting curved lines or circular shapes in cement board with a jig saw fitted with a carbide blade or a fine-tooth, metal-cutting blade.
Place the board on a sawhorse with the front side face-up
Mark the shape of your cut on the material with a pencil.
Drill a 3/8-inch hole somewhere along the line with a masonry drill bit.
Insert the blade into the hole and bring the saw up to full speed.
Push the jigsaw slowly and smoothly along the line.
You may have to use more than one blade for long cuts as they get dull quickly.
Particularly small holes can be difficult to cut with a jig saw. So, instead of using the saw, drill a series of holes all the way around the outline using your 3/8-inch bit. Then, use a hammer to lightly punch out the hole and clean up the jagged edges with tile nippers or pliers.
You can technically use a jigsaw and a masonry drill to make any cuts you need in cement board, including long cuts that span the length of your boards. However, the bits will dull quickly and cut more slowly than a circular saw, so you’re far better off using a utility knife or circular saw for long, straight cuts.
Instead, use your jigsaw to cut out holes for outlets or switches—just drill four holes in the corners of the cutout and then use the saw to connect them and punch out the material—or for any curved cuts.
Cutting cement board isn’t difficult, but there are a few tips you can follow to keep the project moving along as smoothly as possible.
Measure twice, cut once.
Run the blade over the cut line several times when scoring and snapping. The deeper the groove you create, the easier and cleaner the board will snap.
Always work on a clean and sturdy surface clear of tripping hazards and debris.
Avoid using a hole saw to make circular cuts in cement board. The teeth will quickly become dull and render the tool useless for anything in the future.
Cutting cement board with a diamond blade and a grinder is possible and effective. However, the practice isn’t as safe or accurate as using a circular saw to achieve the same cuts.
If you’re planning to do a DIY tile project from scratch, learning how to cut cement board properly is necessary. It’s also an excellent way to save money on your bathroom remodel.
However, cutting cement board creates irritating and hazardous dust, and it just might not be your favorite weekend project. If you have safety concerns or want to save yourself time, a local drywall installer or local bathroom remodeling company can help.
You will spend around $3.00 per square foot for professional cement board installation, which is around $2.00 more expensive than if you installed it yourself. That added cost for labor could be worth it, though, as any mistakes in the backer board installation will likely show in your finished tile work.
The tool you’re using to cut cement board will determine which type of blade you’ll need. Sharp utility knife blades are safer and work better than dull ones when using the score and snap method. Circular saws will perform best while cutting cement board if you use a carbide-tipped, wood-cutting blade with as few teeth as possible to reduce dust production. The blade of choice for your jigsaw is a fine-toothed, metal-cutting blade. Regardless of what tool you use, have extra blades on hand, as they will dull quickly as you work and need replacement.
Cement board has a smooth side and a rough side. Install the board rough side out if you’re installing your tile with thin-set mortar; for instance, in a shower or other wet location. If you’re adhering tile in a dry or damp area with mastic, install the cement board with the smooth side facing out. The rough side is designed to give you ample surface area for thin set to adhere, while the smooth side provides a perfectly flat surface for dry tile work.
There isn’t a true, dust-free way to cut cement backer board, but scoring the material with a utility blade and snapping it will create the least amount of dust possible. This cutting method is slow, but it produces far less dust than any power tool. To keep dust to a minimum using power tools, run the tools at their lowest rpm setting. Fine, metal cutting blades are best for jigsaws, while rough-cutting wood blades are best for circular saws. Using sharp blades on power tools is a great way to keep dust production to a minimum as well.
