Durock cement board is a DIYer's best friend when it comes to tile and construction projects. This durable material resists moisture and mold, making it ideal for bathrooms and high-humidity areas. It's also stronger than plywood, making it useful for floor, wall and countertop installations. You can cut by scoring and snapping or by using a circular saw for straight cuts and hole saws or jigsaws for cutouts.
Proceed With Caution
Before cutting Durock or any cement backer board, set up a work area outdoors. This specialty board produces a very fine silica dust that can be harmful if inhaled or if it gets in your eyes. Wear a respirator, eye protection and work gloves when cutting Durock, noting the wind direction ahead of time. Don't work near open windows or screen doors, as the particles may travel indoors.
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Straight Cuts: The Manual Method
To make a straight cut along a sheet of Durock, mark the desired cutting points with a carpenter's pencil. Measure and mark the starting and ending points for the cut, then line these up with a large, sturdy straightedge.
Drag a scoring tool or sharp utility knife along the cut line, up against the straightedge. Repeat the process a few times to make the score deeper. Lift the piece with both hands and press your knee against the unscored side, holding the board, so the score line is vertical. The board should snap, with the fiberglass mesh inside keeping the pieces connected. Use a sharp utility knife to slice through the mesh, then smooth any rough edges with a rasp.
This technique is most efficient on thin Durock, when you only need a few cuts.
Straight Cuts With Power Tools
Use power tools on large projects or thick Durock to muscle through the process with ease. A circular saw with a carbide-tipped woodcutting blade is the best tool for the job. Opt for a blade with as few teeth as possible.
Unlike cutting wood, the less teeth, the less dust when cutting Durock. Use a straightedge and carpenter's pencil to plot out the cut line, then set the board up on sawhorses or over the edge of an outdoor work surface to make the cuts. Saw along the line slowly and evenly. Wear long sleeves and pants to protect yourself from dust, along with protective eyewear, gloves and a respirator.
While a jigsaw or an angle grinder fitted with a cutting wheel can also cut Durock, these options result in more mess and less accuracy.
Making Holes and Cutouts
As with wood boards, several methods work for making round holes or irregular cutouts in Durock. Create small holes for wiring or narrow pipes by marking the desired location with a carpenter's pencil, then drilling through the Durock with a masonry bit.
Cut wider round holes with a hole-saw bit or by drilling a series of holes around the circle's perimeter with a masonry bit, then connecting the cutouts with a jigsaw outfitted with a carbide or metal-cutting blade. Smoothing out rough edges usually isn't necessary since Durock is an underlayment, but if it is necessary, do it with a file.
Make non-circular cutouts by plotting out the area with a carpenter's pencil, then scoring the area with a sharp utility knife. Slice through the fiberglass mesh with the knife, then tap a hammer within the lines to pop the piece loose. Another option is to drill a few holes along the inner perimeter of the pencil line, then cut along the line with a jigsaw, starting in one of the holes.