How to Cut Windows in a Cinder Block Basement

Measure and mark the outlines of the window on the desired basement cinder block wall using masking tape. Use a carpenter’s level to ensure the lines are level and their ends match up.

Wear safety glasses, ear plugs, a face mask and gloves. Insert a 16-inch-long masonry bit into the drill. Bore a hole at each corner of the window’s outline until it extends to the exterior surface.

Follow label directions to insert a diamond-cutting blade into a 14-inch concrete saw. Insert the end of a garden hose in the water inlet valve on the saw and screw it tight. Turn the water on to a trickle so that it acts as a lubricant and prevents too much dust from forming.

Grasp the saw firmly in your hands and position it along one of the lines along the window. Press the trigger on the saw to cut through the block wall along the outline one-half inch deep. Extend the cut along the length of the line before turning it the saw off.

Position the saw along the scored line on the cinder block wall and cut through it by one-half inch again with each pass. Repeat this process to cut the other three sides of the window.

Step to the outside of the cinder block wall to complete the cut. Locate the four corner holes you had drilled to mark the window’s outline and extend lengths of tape between these. Repeat the process to cut the wall along the outline, forming a 1/2-inch cut with each pass.

Break out the cinder block wall within the scored outline using a 4-pound hammer. Position the hammer against the top middle of the section, and pound it hard to knock off the loose blocks. Continue to knock cinder blocks off the wall, thereby creating an opening. Ensure you work carefully around the corners so you do not loosen surrounding blocks.

Position the tip of a brick chisel against the edge of the wall hole and tap it with a hammer so it smooths out the opening. Continue this along the sides of the hole.