Good point: 5 little known facts about repointing (tuckpointing) brick masonry
/Fired clay brick is extremely durable, routinely demanding little in maintenance over the course of centuries. As a wall system, brick masonry and all of its associated components are also very durable, but over time (usually many decades, at least) the mortar binding the individual brick units together on a facade may come to need some attention.
The process of removing defective mortar from between masonry units and replacing it with fresh mortar is called “repointing” or “tuck-pointing.” Sounds straightforward enough, right? But, the thought of repointing is often intimidating to people, especially with regard to historic structures. There seems to be a mystery surrounding the process — as if the correct (and affordable) way to do it is somehow unknowable.
Here are five little known facts about repointing which may bring you some ease if you are ever called to facilitate a repointing project.
The biggest reason to repoint is to stop water penetration. Obviously, mortar that is crumbling and falling out of mortar joints is an aesthetic problem, and if allowed to progress it could become a structural and safety issue. What’s not obvious is that the force behind the progression of the problem (and often the villain to begin with) is water penetration. Hairline cracks, voids in the mortar, and mortar erosion make it possible for water to seep into the masonry system, further breaking the mortar down and leading to bigger problems.
One part of a facade needing repointing doesn’t automatically mean the rest of the structure needs it too. Only defective joints require repair and, in fact, original mortar joints are preferable to repointed ones. So, if upon visual inspection some joints are not suffering from deterioration, they should be retained intact. Repointing is very labor-intensive work, so “if it ain’t broke, don’t fix it” — a strategy that is good for both the structure and your budget.
Modern and stronger aren’t always better. There’s a temptation to think that an old building will benefit from “upgrades” to today’s state-of-the-art. Mortars have gotten stronger and more durable over the last century, but when it comes to repointing, think old school. The new mortar being slipped into the joint will be next to the remaining old mortar, and they must have similar compressive strengths. If the new mortar is significantly stronger, the portion of the joint made from new stuff will not compress under load in the same way as the older portion of the joint. This creates a pressure point for the adjacent brick and may cause it to spall. The composition of the old mortar can be tested and matched, or assumptions can be made about the recipe of the original mortar based on the structure’s age.
New mortar can be pigmented to match original mortar. A concern with repointing only a portion of a structure, especially if it’s only a portion of a facade, is that the repair will be made obvious by color variations between the original and new mortars. This is a reasonable worry, but excellent masons can accurately tint the new mortar to match the old. The color of the sand used in the mortar mix plays a big role in the final color, and metallic oxide pigments can be added up to 10% by weight of the Portland cement in the mix (carbon black is limited to 2%).
Repointing is not prohibitively expensive in the grand scheme of things. As already noted, repointing is a labor intensive process, and can therefore be expensive. Its cost, though, needs to be weighed against the value that a brick structure delivers over its lifecycle and savings in maintenance costs captured over the same period. By the time any portion of a brick masonry structure is in need of repointing, it’s already enjoyed a maintenance-free stretch far longer than virtually any other material could offer. And, by investing in repointing at the few-and-far-between moments when it is necessary, the full financial and environmental cost of a brick building can be amortized over centuries rather than decades.
For more information and guidance about repointing, check out the Brick Brief from the Brick Industry Association.
