What is a good way to grind out joints for repointing glazed brick masonry?
I am afraid that I will chip off the glaze when grinding. How can I stop this from happening?
Grinding glazed brick masonry for repointing is difficult if the mortar is not badly deteriorated. When the mortar is deteriorated, it can be raked out of the joint without using a grinder or chisel. If, however, the mortar cannot be easily raked from the joint, running a grinder along the edge of the brick likely chips the glaze.
One approach that can reduce the risk of chipping is to grind a slot down the center of the joint. Then use a hand chisel to knock the thin slivers of mortar in towards the center of the joint. This procedure can still result in chipping unless the workman is very skilled. Also, this approach does not work well if the mortar is well bonded to the brick unit.
Where repointing of glazed brick is being performed because of excessive separations or weathering of the joints, I recommend face grouting instead of grinding and repointing. Face grinding is described in BIA Technical Note 7F.
In this procedure, use a mixture of 1 part portland cement, 1/3 part hydrated lime. and 1 1/3 parts fine sand (passing a No. 30 sieve). The grout is mixed with enough water to produce a fluid consistency.
Before applying the grout mixture, the wall is dampened. I recommend cleaning the joints with clean water and then waiting until the water is absorbed prior to brushing on the grout mixture. When done properly, the face grout mixture can be forced into the separations and voids to form a thin layer on the surface.
Because the glaze on the surface of the brick does not absorb moisture and does not allow the grout to bond to it, mortar smears on the face of the brick can be rubbed off with burlap immediately after the mortar has dried on the surface. This process also can be used to help force the grout into the voids and separations. For best results, two applications of face grouting are recommended.
This procedure is cleaner than grinding and does not cause damage to the glazed brick units. However, repointing is required if the mortar is severely deteriorated. Face grouting should only be used when the mortar is sound.