Cutting out and repointing of mortar joints in brick is one of the most common masonry repairs. If the brickwork is left unrepaired, water can seep in between the cracked, loose mortar and cause interior wall damage. The following procedures are recommended to do the job right:
Preparing the Joints
Cut out the mortar joints to an approximate depth of ¾" to 1". Use of a special plugging or joint chisel will help prevent binding in the joint and chipping of the brick edges. A clean surface is needed for good bonding. Use the jointer tool to rake out excess mortar or grit, and brush out the joints to remove loose mortar or sand. Flush out any remaining particles with a garden hose.
Replacing Damaged Bricks
Any bricks in the wall that are badly broken or deteriorated should be cut out and replaced prior to repointing. Select new bricks that match the old bricks as closely as possible. Cut the old brick completely out of the wall. Clean out the recess carefully.
Wet the cavity and the replacement unit with a brush or fine water spray. When the cavity is damp, but not wet, apply a thick layer of
mortar to the bottom and sides of the cavity.
Repointing
Dampen the cleaned joints with a brush and water. Load a trowel with mortar. Pick up the mortar from the trowel with the jointer tool and pack the mortar into the joints. In most cases, joints are filled flush to the wall face, then slightly depressed with the jointer and brushed clean.
"Butter" the top of the replacement brick with mortar and slide it into the cavity. Mortar should squeeze out from the joints. If it does not, add more mortar to the joint.
To decrease the possibility of cracking or sagging in extremely
deep joints, fill in about half of the joint depth, wait until the mortar is thumbprint hard, and then repoint the remainder of the joint.
In hot or windy conditions, dampen the repointed joints to prevent
the mortar from drying too fast. Spray the finished job with a fine
water mist to aid in the curing process.