page_title: Repointing
section_title: Removal of old mortar
hierarchical_section_title: Repointing / Construction process / Removal of old 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: After examination, the next step is cutting away the old mortar. The old mortar is removed to a depth equal to or slightly more than the width of the joint, or to the point where sound mortar is reached. Removal of old mortar between joints is done carefully to avoid damage to masonry units. On buildings with soft materials, such as under-fired brick, lime mortar, or terra cotta, removal by hand is often the most effective to avoid damage.  Hard Portland cement mortar is usually removed with a grinder or power circular masonry blade, taking care not to damage the masonry units. Vertical joints or thin joints are done by hand or with small power chisels." If a power saw needs to be used, it's only used on wide and uniform horizontal joints and in the middle of the joint. A hammer and chisel are then used for the rest of the mortar, closer to the masonry units. Caulking cutters with diamond blades are an acceptable power tool to remove mortar in wide horizontal joints. They are slow, have no rotation, and vibrate so they are likely to cause less damage to the masonry units.
  After the mortar has been cut out, the joints are vacuumed or brushed clean. After vacuuming, the remaining debris is removed with a water jet from the top of the masonry area down.
caption: Removal of old mortar
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