DO THIS, NOT THAT

When repointing butter joints.

New brick houses are predictable: red bricks with light-grey mortar joints 3/8" to ½" thick. It wasn’t always this way. Brick manufacturing was in full swing by the second half of the 19th century, and builders were experimenting with brick colors, brick bond patterns, and mortar colors and joints. A popular variation was the use of a very thin joint—less than ¼" and commonly 1/8" to 3/16"— often referred to as a butter joint. This joint for high-quality brick was sometimes used only on a building’s primary façade. The joint needs repointing less often than do ordinary joints. When it does come time, however, it takes extra time and skill to repoint.

WRONG WAY USING COMMON TOOLS

When removing the deteriorated surface mortar in preparation for repointing, avoid using a chisel or angle grinder, which can damage the brick face. The narrowest, readily available pointing trowels are probably not thin enough for butter joints. Even with care, it is impossible to repoint this type of joint without pressing mortar onto the brick surface, altering the appearance.

RIGHT WAY MODIFYING A TROWEL

To clean the joints to a uniform depth of about one-half inch, use an oscillating tool with a blade designed to remove the grout between ceramic tile. To repoint, file or grind down the sides of an ordinary pointing trowel to the approximate width of the joint. I also find it easier to use if the length of the trowel is shortened by 40% to 50%. Masons have reported that using tape helps limit the amount of mortar staining on brick below.