Old stone steps can deteriorate over time, leaving the mortar between the stones loose or crumbling. If this occurs, it is important to repair the steps to maintain a safe surface to walk on. The mortar between the stones must be chiselled out and repointed with fresh mortar in a two-part process. The first part is called tamp pointing and is followed by finish pointing. Two different mortars are used for the mixes. The end result will be a sturdy repair for your stonework.
Chisel out the loose or crumbling mortar joints in the stone steps until you reach solid mortar, approximately 2 to 3 inches. Tap a masonry chisel with a masonry hammer as you guide the chisel along the joints to clean it out.
Brush any loose debris left behind by the chisel out of the joints, using a wire brush.
Mix seven parts sharp sand, one part lime and one part cement in a mixing trough with a trowel. Slowly add water until you reach a stiff batter-like consistency.
Pack approximately half of the depth of the cleaned-out mortar joints in the steps with the mixed mortar, using the tip of a pointing trowel. This is called tamp pointing.
Mix six parts sharp sand, one part lime and three-quarters part cement in a mixing trough with enough water to create a stiff batter mix, using a trowel.
Fill the remaining depth of the tamp-pointed joints with the mortar you mixed in Step 5, using the point of a pointing trowel to finish-point the joints. Drag the tip of the trowel across the finished joints to smooth the surface.
Inspect stone steps seasonally, and make small repairs to the mortar as needed to maintain the stonework.
Wear eye and hand protection when making stone step repairs.