By Fancey Miller
Historic Bel Air 1740 correctly repointed with lime mortar
If the slime craze taught us anything, it's that a few ingredients mixed in slightly different ratio have different results. It also taught us that kitchen supervision is the mother of cleanliness. Adjustments to a few ingredients is not new. Baking operates in much the same way. Adding or decreasing the eggs in brownies changes their texture. Construction is no exception. Concrete and mortar operate under this principle. Changes to the few ingredients affects the characteristics of concrete and mortar. In mortar the characteristics affected are compressive strength, bonding, and flexibility.
Standard mortar comes in several types with varying levels of Portland cement, lime, and sand. These mixtures have different applications due to the adjustments and subsequent shifts in characteristics. Some are great for building walls, chimneys, or fire pits with rocks, bricks, or blocks. They are higher on the bonding and compressive strength scale but less flexible. Interior work and masonry wall repair require a mortar with lower compressive strength, medium bonding, and higher flexibility.
Historic restoration requires mortar with an extremely low compression strength, medium bonding, and higher flexibility. Historic brick must be treated with care. The higher compression strength mortar is too rigid once hardened. As the home shifts, the softer historic bricks will break against this incorrect mortar.
The grey between the bricks is the incorrect mortar
Just such a thing happened at the Historic Bel Air 1740. Someone came in and repointed the historic home with a mortar meant for modern brick. The newer mortar never blended in with the original. As time wore on, some of the historic bricks began to break. We were asked to come in and repair the resulting damage. There is a recommended mortar for this type of job; However, the ideal solution is to test the original mortar and have mortar mixed to match it. We opted for the test and mix option. While waiting for the results, we removed the incorrect mortar. Then we repointed with the lime mortar mixed to match the original mortar. The result was an amazing finish. We would be glad to help you with your historic restoration project as well.
We used scaffolding and ground out the wrong mortar
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