Whether you’re repointing cracked and crumbling mortar, adding a new window or door in a masonry wall, or joining a new masonry wall to an existing one, the first (and often most challenging) step is to grind and chip out the old mortar. This is particularly hard to do when you need to remove bricks or stones to “tooth in” the new work to the old pattern. Doing this without damaging the surrounding masonry units is a job that requires more than a hammer and a flat chisel.
For years, I’ve used a grinder or a circular saw equipped with a diamond blade, a rotary hammer, and a plugging chisel that I strike with a 2-pound hammer. The diamond blade takes care of the long, straight joints, but it doesn’t fit into short joints, such as the head joints in brickwork. In those tight spots, I’ve used the rotary hammer to perforate the mortar, then used the plugging chisel to knock it out.
I’ve often wondered why tool manufacturers didn’t offer a chisel shaped like my plugging chisel that I could use with my SDS-plus rotary hammer set in chiseling mode. But I can stop wondering now that Bosch has introduced the SDS-plus Mortar Knife. It’s available in convenient thicknesses of 1/4 inch and 3/8 inch, and like my plugging chisel, it’s designed to force the chipped mortar out the face of the joint rather than into the masonry units on both sides of the joint—lessening the possibility of breaking or damaging the unit.
So far, I’ve used the mortar knives to repair a stone wall and a brick staircase, and I would guess that they saved roughly 25 percent in labor time. At that rate, they can easily pay for themselves in one job.
The 1/4-inch version (model HS1400) costs about $18, and the 3/8-inch version (model HS1401) costs about $20. I like having both sizes, but I could get by with just the smaller size—if necessary—because it fits into narrower joints but still works on the wider ones.
John Carroll is a remodeling contractor in Durham, N.C.
