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Terra Cotta: The Rules Have Changed

Richard Koenigsberg

Founder and President, Koenigsberg Engineering 


It used to be that if your building had damaged terra cotta, you could pretty much file for a permit with the Department of Buildings (DOB) for whatever kind of repairs you wanted to do. That’s not the case anymore. Now the DOB wants engineers to replace damaged terra cotta rather than repair it in place. Another big change is with the Landmarks Preservation Commission, which now requires that smaller replacements be done with real terra cotta if they’re below the sixth floor. 



Replacing terra cotta is complicated. Pieces that are repetitive can simply be extruded — think of the old Play-Doh machines that pushed the clay out, which you could cut into pieces. But most terra cotta replacements tend to be made out of molds. The molds have to be 10% bigger than the actual finished piece, because the clay is put on a drying floor, sometimes for months, to get the moisture out before it can be fired in a kiln, and it shrinks. That's what makes terra cotta so much more complicated than making pieces out of other materials, such as concrete, which don't shrink. 

Let's say you have a big lion's head made of terra cotta. If you were going to replicate it with concrete, you could just take a rubber mold of the lion's head, pour the concrete in and you’ve got your piece. But since terra cotta molds have to be 10% bigger, an engineer needs to do technical drawings — specifically, an isometric drawing that is a 3D representation of the object showing the front, back, side, top and bottom views, along with exact measurements. Then the head is carved out by hand and a mold is made from that. 

It’s hard work, and it’s expensive. An average piece could cost anywhere from $1,000 to $2,500. Also, you have to ship the original pieces to the manufacturer, and some of these can weigh 600 or 700 pounds. Even with a smaller, simpler replacement, if the piece is missing or damaged to the point where it's unrecognizable, you're going to need to pull a piece out of the building and send it to the manufacturer. 

When we survey a building, we look at every single piece of terra cotta and make a set of drawings that identifies each one, along with its condition. I rate each piece on a scale of one to 10 — 10 meaning it must be replaced because it’s missing or damaged beyond repair. Nine would be very severe damage. Pieces that are rated six or seven are pretty damaged but don't absolutely have to be replaced. I might be able to pull the piece out, repair it and reinstall it, which you want to do whenever possible because the molds are such an expensive process.



When you're doing Facade Inspection & Safety Program repairs and terra cotta is involved, you have to factor in extra time to get the work done. Manufacturers will tell you they can make a piece of terra cotta in four months and that's generally true, even though there’s a little more of a backlog now than before. But that's four months after they have approved the shop drawings, which takes time. You send the damaged piece, the manufacturer measures it and does drawings, and then sends them back to you for your engineer to review. You need to verify that each piece is measured perfectly — and when I say perfectly I mean you want to be accurate to within 1/16 of an inch. Then there’s the challenge of getting the proper color match, which can also take months. White is especially difficult. I’ve worked on several buildings with white terra cotta, and the white is different on every single one. 

In the meantime, you might have scaffolding and a sidewalk shed set up because you’re doing other facade work. But let's say you've finished that and are still waiting for the terra cotta replacements. Do you still keep the scaffolding and sidewalk shed there? You’re starting to see buildings in New York City doing terra cotta repairs that are covered with plastic for eight months or even longer, partly because they don’t necessarily happen vertically, but can be scattered all over the building. 



Planning is crucial. If you plan properly, you’ll know exactly what you’re facing and how much time will be involved. There are a lot of qualified engineers who know how to repair facades in New York, but I wouldn't consider using an engineer who hasn't replaced terra cotta on at least a dozen buildings, because terra cotta is simply a different animal. Just as important, you also want experts who know when you don’t have to replace terra cotta, because not every building needs custom replication and it’s just so costly.

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