Techniques > Briefs > Repointing Mortar Joints > Execution of the Work >


• temperature
• plastic
• burlap
• misting using a hand sprayer with a fine nozzle
• scaffolding

Curing Conditions

The preliminary hardening of high-lime content mortars — those mortars that contain more lime by volume than portland cement, i.e., Type O (1:2:9), Type K (1:3:11), and straight lime/sand, Type "L" (0:1:3) — takes place fairly rapidly as water in the mix is lost to the porous surface of the masonry and through evaporation.

A high-lime mortar (especially Type "L") left to dry out too rapidly can result in chalking, poor adhesion, and poor durability.

Periodic wetting of the repointed area after the mortar joints are thumb-print hard and have been finish tooled may significantly accelerate the carbonation process.

When feasible, misting using a hand sprayer with a fine nozzle can be simple to do for a day or two after repointing. Local conditions will dictate the frequency of wetting, but initially it may be as often as every hour and gradually reduced to every three or four hours.

Walls should be covered with burlap for the first three days after repointing. (Plastic may be used, but it should be tented out and not placed directly against the wall.) This helps keep the walls damp and protects them from direct sunlight.

Once carbonation of the lime has begun, it will continue for many years and the lime will gain strength as it reverts back to calcium carbonate within the wall.