For such a simple material, architectural terra cotta has been causing a lot of complications lately. It’s pretty much just clay mixed with ground-up, pre-fired clay, pressed into a mold to achieve a shape, then fired in a kiln to become a ceramic building material. It can be glazed or left unglazed. It has been around for thousands of years and can be found in the architecture of many ancient civilizations, including the Romans’. Today it can be seen on hundreds of New York City co-op and condo buildings of a certain age.
When it’s not properly maintained, terra cotta can work loose from building facades, with potentially tragic results.
Terra cotta was first used as decorative flourishes on New York buildings in the late 19th century, when it was usually built into load-bearing masonry walls, a very secure system. Builders loved it because it’s easy to mass produce, infinitely pliable, and often just plain beautiful. It’s also cheaper than carved stone. As the 20th century unfolded, developers saw steel frames as a way to build bigger, faster and cheaper, and they began using the steel to support both floors and facades. In such iconic structures as the Flatiron Building and the Chanin Building facing Grand Central Terminal, terra cotta was increasingly hung from steel supports rather than incorporated into masonry walls. And this is the root of most terra-cotta facade problems in New York today.
Terra cotta was originally thought to protect the steel elements that support it from water and the resulting corrosion (rust) that is the primary cause of steel decay. Unfortunately, a terra-cotta skin cannot protect the vulnerable steel and iron anchors and supports embedded in a wall forever. Over time, those metal elements can corrode and expand to many times their original size. This can crack and spall the terra cotta and brick infill that surrounds the supports, and the result is the dangerous possibility that a piece of masonry may detach and fall to the street below.
So what can a co-op or condo board do to keep this from happening?
Since the passage of Local Law 10 of 1980, now known as the Facade Inspection and Safety Program, or FISP, the city has mandated that owners of buildings taller than six stories inspect their facades every five years and repair them as necessary. These rules have recently been tightened, and fines for noncompliance have been stiffened.
It is particularly important for co-op and condo boards to have their buildings’ terra cotta inspected by professionals who are experienced in this type of masonry. Architecture and engineering schools typically do not provide any grounding in the unique challenges facing those entrusted with the care of these archaic wall systems. As a result, the professional must rely on experience and a good practical understanding of the construction at hand. Do not assume that any licensed professional has the knowledge required to adequately assess the condition of century-old terra cotta.
Inspections should include as much hands-on contact as possible. A visual inspection is not good enough. Instead, terra cotta should be sound-tested to gauge whether or not there is any internal damage from corroding supports or anchors. This involves tapping each piece with a metal hammer and judging its integrity by the sound and the vibration caused by the hammer blow. This requires training and experience.
Other test methods include sonic-resonance testing and penetrating radar, but because of the relatively high cost of these tests, most inspections are performed using traditional sounding methods.
Boom Trucks a Boon
Inspections have been made somewhat easier recently by the greater availability of personnel lifts, also known as boom trucks. This allows inspectors to investigate multiple areas of the facade without costly scaffolding, and the need for further precautions and work can be easily assessed. Of course, if there is any imminent danger of detaching masonry, a sidewalk shed or other code-compliant pedestrian protection measures should be put in place immediately. If terra-cotta repair or replacement is required, the same care should be used in selecting a professional to implement the repairs. New terra cotta is available from two American manufacturers, and it should be the first choice in any repair project.
To sum up, one of the big reasons the buildings of New York are so beautiful is the presence of so much architectural terra cotta. We can continue to enjoy nice things – if we know how to take care of them.
Dan Allen is a principal at CTA Architects and a recognized authority on terra cotta.