How to Cut a Doorway Into Block

Mark the opening on your concrete wall using a tape measure and level. The opening should be as wide as your door plus 3 inches for the door frame. For example, if you plan on installing a 32-inch door, the width of the opening should be 35 inches.

Measure the height of the opening so it equals the height of your door plus 3 inches of extra room for the header and the door frame, as well as a bit of adjustment room. Outline your wall opening measurements with masking tape. Use your power drill and masonry bit to make pilot holes at each corner of the doorway opening from the inside through to the outside of the wall.

Cut all the way around the tape outline along the perimeter of the doorway opening using a circular saw with a masonry blade. Cut a 1/2-inch groove outward to both sides from the corners formed by the top and the sides of the opening. The cut should extend about 4 inches past the side of the opening outline on both sides. The cut should be 1/2 inch in width so a steel lintel can be installed for top end support.

Move to the outside of the wall and trace the outline of the doorway opening with masking tape and a straightedge, using your pilot holes as a guide. Use your hammer or a small sledge to knock blocks out of the wall. Start at the top of the wall and slowly work your way down until the opening is clear. Use a masonry chisel to knock away any chunks of block that were not cut clean away and create as smooth a doorway edge as possible.

Insert the steel lintel into the groove you cut at the top of the door opening. Use your trowel and fingers to fill both ends of the groove with mortar that has been mixed slightly more dry than normal. Use your hammer to drive the lintel into position, and allow the mortar to dry according to the manufacturer's instructions.