How to Repair Stone Walkway Mortar
Fixing up the cracks between paving stones keeps a walkway beautiful and safe
Q: The mortar joints surrounding the stones in my walkway are crumbling. Can they be patched? —Nellie Kurtzman, Mount Vernon, NY
Martin D'Arcy, owner, DNF Construction, replies: A stone walkway with cracked mortar is an eyesore and can become a tripping hazard if water gets underneath and loosens the stones.
The best way to repair these joints is with a sand-topping mortar mix, which is stronger than regular mortar and can handle wider joints. I mix it with an acrylic fortifier so that the joints will be less susceptible to water penetration.
The hardest part of this job is chipping out the crumbly old mortar without damaging the stones. Once the old stuff is out, filling the joints is as easy as decorating a cake. Just keep in mind that while the new mortar won't match the existing mortar color, it will lighten and blend in over time. The only way to get the same shade would be to replace all the old mortar, crumbling or not.
Tackle this job only when there's no danger of frost. A two-day dip into the 20s F can ruin fresh mortar.
Chisel Out the Mortar
Wearing gloves, safety glasses, and knee pads, break out the crumbling mortar with a cold chisel and 3-pound sledge. Chisel right down to the setting bed; be careful next to the stone or use a grinder with a diamond blade to carve out difficult spots. Clean out the joints with a stiff-bristled nylon brush.