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Repointing is the process of removing and replacing deteriorated mortar from historic mortar joints. A historic building should only be repointed when and where absolutely necessary. Improper repointing can not only negatively affect a building’s appearance, but also can cause irreversible long-term deterioration of stone or brick. Historic mortar was a soft lime-based material meant to serve as a sacrificial expansion joint to allow for bricks or stones to expand and contract. If historic mortar is replaced with mortar that is harder than the surrounding stone or brick, the new mortar will not allow for necessary expansion and can cause the masonry to chip off, or spall. To preserve the visual character of the building, new mortar should also match the historic mortar in color, texture and tooling. Property owners should proceed with a repointing project only in consultation with a preservation architect and experienced historic masonry contractor.
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