One of the distinguishing characteristics of the homes in Mt. Lebanon is the beauty and variety of their brick masonry construction. These building skins are the public face of our community, and appreciating this ancient construction material helps us understand the importance of preserving our aging housing stock. In addition to being aesthetically pleasing, brick is a remarkably durable material that excels in weather resistance, strength, thermal mass, acoustical isolation and fire resistance. It does, however, need to be maintained to retain these qualities.
This region has a vast number of brick houses because clay is abundant nearby and there has always been plenty of coal or natural gas to fire it. Even today, there are three brick manufacturing plants within a two-hour drive of Pittsburgh. Because of its weight, shipping brick can be expensive, making the product less affordable in areas of the country that are not close to brick plants.
Historically, clay bricks were manufactured to just about any shape and size that could be fired in a kiln. Prairie Style homes designed by Frank Lloyd Wright were built of long thin bricks, referred to as “Roman brick,” because they were of dimensions similar to those found in ancient Roman construction. The most common brick size today is referred to as “modular.” It is eight inches wide measured from the centerline of adjacent mortar joints. Vertically, three modular bricks stacked upon one another is also eight inches.
Notice the great variety of colors of brick homes in Mt. Lebanon. Designers and contractors have access to bricks of many natural earth colors ranging from deep reds and pinks to buff, beige, browns and oranges. A brick wall can be a consistent color or include a range of colors. Blending bricks fired from different clays can create the range, or it can be found in the variety of “flashed” bricks from a single firing. Traditional coal fired kilns produced much more diversity and range than more modern gas fired kilns. Some bricks are covered with fine speckles, especially those in the buff and orange colors. These are iron spots, an expression of the minerals in the clay.
Mortar is the cement material placed between individual bricks. Experts debate whether it holds the bricks together or keeps them apart; of course it does both. Mortar color is primarily derived from sand. It can be colored to match almost any existing mortar by adding natural pigments or using pre-mixed colored masonry cement. The final shape of the mortar joint is determined by how the mason strikes it off. The most common profile is concave, but it can be raked, beveled, or struck flush. Each profile gives the wall a different appearance. A well struck joint will improve the weather resistance of the wall.
“Bonding” describes how the bricks are laid in the wall. Each arrangement of bricks results in a different pattern of mortar joints. The most common is the “running bond,” where each brick is stacked on top of the one below it but shifted horizontally one-half of the width of the brick. There are many other bonds, some derived from early construction techniques (English bond) and some contemporary (stacked bond).
Brick and mortar create a superb building cladding. Brick veneers act as a primary line of defense to wind-driven rain, but cannot be expected to be watertight. If properly designed, brick veneers should direct penetrating water to run down the back side of the brick and be drained, or weeped, to the outside with metal or flexible flashing.
By the time a home reaches 75 years old the mortar has weathered to a point where it may need maintenance. Here are a few things to consider when evaluating the brick in your home:
- Never sandblast brick. This will create permanent damage to the fired face of the clay, leaving it vulnerable to water penetration and accelerated deterioration. The suburbs typically had cleaner air than the city, so cleaning of the masonry is not often a concern here.
- Tuck-pointing is appropriate where there is deteriorating mortar joints, structural damage or excessive moisture penetration into the wall. Pointing involves removing the loose or cracked mortar to a specified depth and putting new mortar into the open joint.
- When removing the mortar, the brick is vulnerable to chipping along its edges and a good mason will avoid this. Using a hammer and chisel to remove the mortar is the most tedious and careful approach. Cutting a kerf in the mortar with a power tool and then removing the remaining portions by hand with a chisel is less desirable due to the possibility of damage to the brick edges.
- Joints should be filled to match the depth and profile of the original mortar. There is a tendency to just fill with mortar those joints originally struck deep between the bricks. This drastically changes the appearance of the wall and is not acceptable.
- Hire a mason with experience in brick restoration. Ask for references and check out local projects. Make sure the mason provides a sample for your approval.
- Stand at least 20 feet away when you check to see if new brick and/or mortar match an existing wall. Let the new mortar cure for several days to reveal its final color.
Joel Cluskey, AIA, CCS is a Mt. Lebanon architect, member of the Historic Preservation Board and Principal at RSH Architects on Vanadium Road in Scott Township. —firstname.lastname@example.org.