ask This Old House

My fireplace has some cracked bricks. Can I cut them out and replace them without causing further damage?

—BYRON BARBOUR, MISSION VIEJO, CA

TOH MASON MARK MCCULLOUGH: Sure you can. As long as you have the right masonry tools, and materials that match the existing fireplace, in most cases the technique of removing and replacing bricks is fairly straightforward.

The hardest part of this kind of project is finding replacement bricks. Take pictures and measurements, then visit masonry supply stores, both local and online, to identify bricks of the same size, color, and texture. With luck, you’ll turn up just the ones you need.

For tools, you’ll need an angle grinder with a diamond blade to cut the mortar; brick chisels and a 3-pound hand sledge to chip out the broken bricks and the surrounding mortar; four trowels—margin, brick, pointing, and tuck-pointing—to mix and apply the mortar; a jointer to shape it; and a wet/dry vac and a stiff brush to sweep away debris. Safety goggles and hearing protection are a must when chiseling or grinding. And because cutting and mixing mortar generate silica dust, be sure to wear an N95, R95, or P95 respirator during those steps, and enclose the work area in plastic.

To extract a brick without damaging the others, you first have to cut or chisel out the mortar around it. Use the grinder to cut into the horizontal mortar joints—the bed joints—above and below the cracked brick. Then, with a cold chisel, cut into the vertical head joints at the ends of the brick. Do not use the grinder on head joints because it will slice into the bricks in the courses above and below.

Once the mortar surrounding the brick is cut or gone, take a big chisel and hand sledge