Cutting Cement Board for Bathrooms

Step 1 - Preparation

Ensure you are working in a well ventilated area, and that your workbench is safe and secure on a stable surface. Safety glasses and a mask should be worn when using the jigsaw, for protection from any debris, and it would also be advisable to wear a pair of sturdy boots, to ensure you are in a stable working position. Keep your jigsaw unplugged and at a safe distance away from you when not in use, and gather the rest of your tools onto your workbench.

Step 2 - Measure and Mark

Use your tape measure to measure the area the cement board will be covering, then transfer your measurements onto both sides of the cement board, using a marker pen and a ruler. Make sure your marks line up correctly.  

Step 3 - Score and Cut your Board

Take your utility knife and run the blade along the marked lines on the cement board, to score. Repeat on the other side of the board, and make sure you score through the outer mesh on all cuts.

Hold either side of the cement board and snap along the scored lines to separate the material. For a smooth finish, use a wood rasp to file the rough edges. To cut non straight lines, use a jigsaw. Apply the saw with even pressure, and follow the marked lines in slow steady movements. Smooth the cut edges using a wood rasp.

selected from: https://www.doityourself.com/stry/cutting-cement-board-for-bathrooms