Rock walls are functional and aesthetic additions to property. Rock walls can act as barriers to hold dirt in place, serve as property line markers, or hold raised flowerbeds. Adding mortar between the rocks bonds the pieces to form a strong wall. Due to age, accidents or exposure to weather conditions, mortar can chip, break and crack. Repairing the mortar will restore the structural integrity and revive the look of the wall.
Use your fingers to pick out pieces of loose mortar. Chip out pieces of damaged mortar with a masonry cold chisel or cape chisel and hammer. Position the chisel into the mortar line at a 45-degree angle, beginning 2 to 3 inches past the damage in each direction. Lightly tap the hammer to crack and dislodge the damaged mortar.
Scrape out small stuck bits of mortar with a wire brush or masonry grinder.
Sweep away dust, debris and dirt from the mortar joint with a small hand-held broom.
Mix mortar with water and a latex bonding agent according to the manufacturer's directions in a small trough or bucket.
Spray the mortar joints with a light mist of plain water from a spray bottle or garden hose. Repairing dry joints will result in crumbling mortar because the existing masonry will pull the water out of the new repair.
Pick up a trowel full of mortar and place it on a mortar hawk. A mortar hawk is a flat tool with a handle underneath to hold mortar while you are working with it.
Position the hawk under the line of the mortar joint and hold it firmly in place to catch excess mortar. Use a pointing trowel to pick up mortar from the hawk. Press the mortar into the void mortar joint and pack it in place with the tip of the trowel.
Wipe the excess mortar off the pointing trowel onto the hawk. Use the clean tip of the pointing trowel to smooth the mortar and level it with existing mortar.
Allow the mortar to set up for 30 to 45 minutes. Match the existing mortar joint finishes. Use a convex jointer to create a slight depression in the mortar joint. Place the convex jointer onto the joint and press firmly. Pull the tip of a pointed trowel through the mortar to create a V-joint. Drag a raking tool through the mortar to form a deep recess. Build up joints with excess mortar and allow the mortar to drip slightly to form an extruded joint.
Spray a light mist of water over the repair and cover it with a heavy plastic tarp. Continue to mist the water joints for seven days to allow the mortar to cure properly.