Repointing Mortar Joints in Historic Masonry Buildings
by Robert C. Mack, FAIA, and John P. Speweik
Masonry--brick, stone, terra-cotta, and concrete block--is found on nearly every historic building. Structures with all-masonry exteriors come to mind immediately, but most other buildings at least have masonry foundations or chimneys.
Although generally considered "permanent," masonry is subject to deterioration, especially at the mortar joints. Repointing is also known simply as "pointing" or somewhat inaccurately "tuck pointing". (Tuckpointing is primarily a decorative application of a raised mortar joint or lime putty joint on top of flush mortar joints to produce an illusion of a thinner or wider joint) Repointing is the process of removing deteriorated mortar from the joints of a masonry wall and replacing it with new mortar.
Properly done, repointing restores the visual and physical integrity of the masonry. Improperly done, repointing not only detracts from the appearance of the building, but may also cause physical damage to the masonry units themselves.
The purpose of this brief is to provide general guidance on appropriate materials and methods for repointing historic masonry buildings and it is intended to benefit building owners, architects, and contractors. The Brief should serve as a guide to prepare specifications for repointing historic masonry buildings.
It should also help develop sensitivity to the particular needs of historic masonry, and to assist historic building owners in working cooperatively with architects, architectural conservators and historic preservation consultants, and contractors. Although specifically intended for historic buildings, the guidance is appropriate for other masonry buildings as well. This publication updates Preservation Briefs 2: Repointing Mortar Joints in Historic Brick Buildings to include all types of historic unit masonry.
The scope of the earlier Brief has also been expanded to acknowledge that the many buildings constructed in the first half of the 20th century are now historic and eligible for listing in the National Register of Historic Places, and that they may have been originally constructed with portland cement mortar.
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