page_title: Repointing
section_title: Filling in new mortar
hierarchical_section_title: Repointing / Construction process / Filling in new mortar
caption_attribution_description: Repointing continues on the Cannon Building's stone facade. Phase 1 of the Cannon Renewal Project began in January 2017 and is scheduled to be complete in November 2018. The entire west side of the building, from the basement to the fifth floor, is closed. Work includes demolishing and rebuilding the fifth floor, conserving the exterior stonework and rehabilitating the individual office suites. Full project details at www.aoc.gov/cannon.
context_page_description: Repointing is the process of renewing the pointing, which is the external part of mortar joints, in masonry construction. Over time, weathering and decay cause voids in the joints between masonry units, usually in bricks, allowing the undesirable entrance of water. Water entering through these voids can cause significant damage through frost weathering and from salt dissolution and deposition. Repointing is also called pointing, or pointing up, although these terms more properly refer to the finishing step in new construction.
context_section_description: The areas with the deepest recession of mortar are filled first. The mortar is placed in several layers, starting with the first layer of 1/4 inch. It is hardened to a desired strength then another 1/4 inch layer is added. The process is continued until the mortar is flush with the masonry. High-lime mortar dries rapidly, so after it reaches a particular strength it needs to be sprayed with water to avoid chalking, poor adhesion, or poor durability. The structure is misted every two hours for two days, then every four hours for two days. It is important that the mortar stays wet for at least a couple of days while it is setting. The local conditions will control how long the structure should be kept wet, however. Burlap or plastic is placed over the repointed wall or structure. This keeps the building damp and eliminates direct sunlight. The burlap and the plastic are not resting against the structure, however. The burlap or plastic are anchored to the ground to avoid this.
  There are different ways to lay the mortar close to the edge of the brick. Some contractors bring the mortar to the very edge, flush with the face of the brick. Others leave it recessed back to allow water to shed off the building. There are three types of recessed mortar: bucket handle, weatherstruck, and simply recessed. The bucket handle is when the mortar is in a curve shape away from the face of the brick. Weatherstruck is when the mortar starts close to the bottom brick and recesses back as it goes up towards the upper brick. The third, recessed, is when the mortar sits back from the face of the brick. There is also tuckpointing, when there are two types of mortar used and the surface one matches the color of the masonry.
  If the color of the new mortar is still not similar to the old mortar after repointing and setting, the non-repointed areas of the structure can be cleaned. This may bring the colors closer together. To do this, a low pressure water jet is used to clean the old pointing. A high powered water jet is not to be used because this could damage the masonry and mortar. Chemicals are also not used with the water because this could be harmful to the masonry or mortar. However, if chemicals are used, the structure is rinsed afterwards with fresh water and natural or nylon brushes. Another method to match the colors is to stain the new mortar. This is not recommended by professionals though, because it can be harmful. If stain is used, the application is tested in the test panel.
caption: Layering New Mortar
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