How to Make a Doorway in a Masonry Block Wall

Measure the width and height of the door that you wish to install into the doorway that you’re creating with a tape measure. Add 2-inches to the width and 1-inch to the height to leave room for the doorjamb installation. Mark the adjusted measurements onto the wall with a piece of chalk, and then outline the marked area using a straightedge and chalk to create a cutting template.

Mark a second area onto the wall above the marked doorway for making a cut to place a steel header above the doorway opening and evenly distribute the load of the wall above the door. Center the header over the doorway marking, marking a box 6-inches high and extending 6-inches on both sides of the marked opening.

Drill holes through the block wall at all corners of the two rectangles comprising the doorway opening and the header opening. Go to the other side of the wall and draw lines with chalk to connect the holes using a straightedge to reproduce the markings on the first side of the wall.

Attach a masonry saw blade to the circular saw. Place the base of the saw against the wall and then trigger the blade to cut through the blocks along the marked lines. Use multiple passes of the blade, cutting in 2-inch layers until you’re about four inches deep into the block. Move to the other side of the wall and cut through that side in layers as well, until you complete the cut entirely through the block.

Break through the blocks from the center of the cut section with a sledgehammer. Work your way from the center of the blocks to the outside edges against the surrounding blocks.

Cut sections of 2-by-4-inch wooden planks to the heights of the partial blocks and place the wooden blocks into the exposed openings within the sides of the masonry blocks, if the opening is greater than 1-1/2-inch in depth. Butter the sides of the block with thinset mortar to get it to adhere to the masonry block. Cover each opening with thinset mortar using a trowel, even those without the needed blocks, to create a smooth even surface on which you can attach the doorjambs.

Measure the header space with the tape measure, then purchase one cut to fit. Butter the edges of the steel header with thinset mortar and place it into the space above the doorway, applying as much mortar as needed around the header to fill the joints between it and the surrounding masonry blocks. Allow the thinset to dry overnight before attaching the doorjamb.