Traditional Masonry Archives — Managing Moisture

Stabilizing Traditional Masonry Buildings

When a wall is distressed, people can see cracks, movement, leaks, leaning or separation between the masonry face and the backup. When pieces begin to fall off, the wall is sending a message that cannot be ignored. Stabilize, or someone will get hurt.

Alan Pettingale of Specialized Masonry Restoration in McKinney, Texas, remembers hearing, “An old building is as dangerous as an 18-wheeler with steering failure — and the truck is inspected every year.”

Of course, at this point emergency steps are required. For a low-rise building, emergency shoring or bracing may be enough to hold things in place until a long-term repair can be made. For higher buildings, it is critical to have nets or covered sidewalks below to prevent injury from falling debris.

Safety is the most immediate concern, but John Speweik of U.S. Heritage Group Inc. in Chicago warns that any emergency procedure must be reversible to avoid making things worse. “Don’t fix a leak or crack with a caulking gun — even caulk can be damaging,” he says. Injecting or attaching incompatible materials can accelerate deterioration or make restoration impossible.

Defining the problem, identifying the solution

The root cause of destabilization is movement. Earthquakes are an obvious, if rare, culprit, but movement can be attributed to foundations shifting or sinking, material degradation, or inadequate connections between building components. With emergency stabilization in place, the structural engineer begins the detective phase of the project — why is the building unstable and what should be done?

In the old days the only way to discover the cause and extent of a problem was to tear down part of the wall. Today, historic buildings are the beneficiaries of the latest high technology. Michael Schuller, P.E., president of Atkinson-Noland & Associates in Boulder, Colo., describes some of the nondestructive methods his company uses to conduct a condition survey. The condition survey answers two questions — how was the building originally constructed, and what is its current condition? “If we see a wall that’s leaning, first we want to see how it was built originally,” Schuller says. “We use microwave radar, ultrasonics or infrared thermography to understand the wall. The objective is to avoid taking anything apart.” The most invasive technique they employ is to drill into a mortar joint and look into the wall with a fiber optic borescope.

Wayne Ruth, president and CEO of Masonry Solutions International in Hunt Valley, Md., stresses the importance of understanding the inconsistencies in the wall. For example, “Individual bricks from the same batch may have different characteristics depending on how close they were to the heat source in the beehive kiln,” he says. Ruth cites different backup materials and differences in weathering based on the wall’s orientation. Finally, “Of all variables, the greatest is the peculiarities of the individual mason,” he says. He stresses the importance of understanding the characteristics of all the materials as well as the nature of the failure when deciding how best to stabilize a historic building.

The condition survey reveals that, as much as we revere traditional artistry, older construction techniques were often inadequate. Many times floors or roofs were simply set on top of masonry walls with no connection except gravity and friction — essentially a stone house of cards.
In other cases metal connectors have corroded. Mike Ferrell, North America general manager for Cintec, a manufacturer of grout anchors, describes a case where rain infiltrated a terra cotta facade and degraded the metal hangers. “We put a camera in a chase in back of the brick backup block,” he says. “What was left of the hangers looked like spaghetti — tiny filaments of wire hanging loose.”
So the object of the condition survey is to identify the source and extent of the problem and identify a solution that will both stabilize the building and solve the problem that caused the destabilization in the first place.

Tying the building back together

“From a design standpoint it’s easy to tell a client to take a wall down and rebuild it,” says Schuller. “The more creative challenge is to keep it there. We specialize in stabilizing facades in place.” There are several techniques for doing that while preserving the aesthetics of the wall.

The most extreme movement situation is foundation shifting. If this is the problem, “this is expensive to fix,” says Schuller. “You have to go deep enough underground and underpin the foundation.” Fortunately, in most cases the solution is above grade — establishing connections, tying the pieces together so they are not going to move anymore.

Pettingale describes strut systems and plate or patres systems used in the United Kingdom to absorb loads in leaning or cracked walls. “Most times if you know what you’re doing there are systems that can actually save a building with up to four inches deflection on the wall,” he says.

These external anchors are effective and are historically sympathetic, but they do alter the appearance of the building. There are modern techniques that tie the building without altering its appearance. “Our goal is to disturb the aesthetics of the wall as little as possible,” says Ruth.

Dry-fix helical anchors offer the most cost-effective building tie system. They can be used for pinning or tying the face brick to the backup and work best for low loads. A quarter-inch pilot hole is drilled through the face and backup masonry and a steel tie is driven in with a hammer drill. According to one manufacturer, Helifix Ltd., these anchors are flexible enough to accommodate movement and do not stress the masonry. Once they are installed, they can be concealed so there is no interruption of the traditional appearance.

When a connection must carry a structural load, such as when it ties the facade to a floor or roof, Schuller recommends using cementitious grout-injected anchors.

Compatibility is key here. A grout that is too strong can damage the host material. Chemical resins, as opposed to cement-based grouts, are usually harder than the masonry substrate, and they risk stressing it. They also have low flammability and can in some cases accelerate the spread of flame, according to Ferrell.

Sometimes the relationship between building components is so degraded that they are impossible to anchor together. Ruth described one such building as “300,000 bricks flying in close formation” — they were all aligned but not attached. Simply repointing the mortar would improve the appearance, but not the stability. Ruth’s company specializes in injection techniques using compatible injected fill (CIF), materials carefully formulated to match the strength, vapor transmission and movement characteristics of the original masonry and mortar.

The resulting CIF is very fluid so it can be injected through the openings used for the condition survey and penetrate small fissures. All the constituent materials are natural — there are no epoxies or other “new-age” ingredients. “The material needs to be sympathetic,” says Ruth. “It needs to behave in the same way as the host masonry.”

Injection makes the wall much more stable, Schuller explains. “Injection makes the wall a single entity instead of a collection of pieces separated by voids and hollows.”

New standards for old buildings

Alan Pettingale believes America is behind in developing standards and guidelines for repairing unstable masonry buildings. “America is crying out for design systems that work to save historic buildings,” he says. “Anyone can build, but putting a building back together is a surgical art form.” Still, there are signs that progress is being made. The Masonry Society is working on standards for evaluation. New York City and other municipalities have ordinances requiring periodic inspection and masonry repair. Most importantly, owners are working with specialized engineers and contractors who have the skills and commitment to stabilize and rejuvenate our structural heritage.

TM