1. Mortar that is cracked, missing or deteriorating.
2. Mortar that has been pointed (tuckpointed) improperly causing adverse effects.
Masonry that is experiencing mortar failure is subject to the adverse effects of direct water penetration and a weakened wall. The obvious weakening that occurs is from a lack of material (mortar) between layers of masonry which derives its primary stability from the weight of the material above it. The freeze thaw cycle causes rapid expansion and contraction within a wall which can cause visible problems such as spalling and in extreme cases cause complete disintegration of the masonry unit.
Modern mortars are much too hard and water resistant for re-pointing old masonry walls. When these mortars are used for historic masonry walls, the long term effects can be disastrous. Not only do modern mortars create a potential detraction from the historic character of the wall, they can actually cause the masonry units to fail. Mortar should be a softer material than the masonry around it. If there are stresses on the wall from water or building movement, the mortar is considered a “sacrificial” material. Meaning, if there is excessive movement in the wall, the mortar should fail first hopefully cushioning the masonry units around it. It’s certainly preferable to re-point mortar than to replace broken masonry units.
The Kansas City area is in one of the worst freeze/thaw cycle zones in the country. During winter, temperatures often fluctuate above and below the freezing point. This allows water to enter problem spots and cracks and re-freeze, causing expansion and breakage problems for our brick and stone structures if they are not maintained.
If there are cracks, missing bricks, and or crumbling masonry/mortar joints, these conditions do require maintenance which includes Re-pointing.
Re-Pointing is the repair process of removing old and corroded mortar from around brick or stone to a correct depth without damaging the wall or the masonry unit. Then “pointing” or placing, compacting and tooling the correctly formulated mortar to the wall being repaired.
Done correctly, a pointing job will last many years, enhance your building’s appearance and will act to prevent water damage and help stabilize the masonry wall.
Joshua Dunn is the owner of Alliance Restoration LLC, a Kansas City based masonry restoration contractor and consulting service that focuses on traditional methods in masonry construction and up-to-date preservation techniques to maintain our built heritage.