By Brian J. Pape, AIA, LEED-AP
If zoning and dampers sound like Greek to you, then here is a primer on super tall skyscrapers in New York City.
Zoning: You can’t build a skyscraper in NYC if zoning won’t allow it. Zoning was established as a legal right of governments in 1916, when New York City adopted the first zoning regulations to apply city-wide as a reaction to construction of the skyscraper Equitable Building at 120 Broadway.
By the late 1920s most of the nation’s municipalities had adopted a set of zoning regulations, mostly modeled after NYC zoning. If you wonder what cities would be like without zoning, go to Houston, Texas, which never had any. It relied on development regulations and deed restrictions, but generally required large lots and lots of parking, leading to urban sprawl and wild mixtures of adjacent uses.
Current NYC zoning is so complex, architects and developers often take special classes to help figure it out. Although some aspects are straightforward, the fine print makes it more complicated. As an example, some of the West Village is zoned R6; R means Residential, and 6 means a total floor area of six times the lot area can be built above ground. Sound simple? You can’t stop there. Zones can also have easements, setbacks, and special provisions. Air-right laws mean adjacent properties can sell their unused floor area to another development, as in the recent case of the Art Students League on 57th Street selling theirs for almost $55 million to the Extell Development next door.
Residential zoning also allows some non-residential uses. Much of Greenwich Village has height restrictions, so even if otherwise allowed by zoning, you still can’t build above a certain height.
And here is an additional loophole that has been used by super tall buildings: “Mechanical space simply isn’t counted toward zoning floor area,” explains Mitch Korbey, a land-use attorney with Herrick Feinstein. So the higher priced apartments can be bumped higher by a tall mechanical space below, 20 feet high or more. There is a practical limit, but more complex heating, cooling, and water filtering systems need more space, and if they are in a flood district, getting that equipment off the ground is essential too.
Dampers: Now if you are going to build tall, you are going to be battling the wind; it is nearly impossible, and it would be very expensive, to try to build so rigid a frame that the wind (not forgetting earthquakes, even in NY) won’t move it. I’ll never forget going to work on a 50-story 6th Avenue office building when it was a bare, open floor; with no obstacles blocking panoramic views from Central Park to New Jersey, the movement of several feet could make one seasick!
So in the 1950’s, engineers began deploying a device mounted in structures to reduce the amplitude of mechanical vibrations caused by wind: it’s called a tuned mass damper, also known as a harmonic absorber. Their application can prevent discomfort, damage, or outright structural failure.
Visit one of our tall observation decks in the city, and appreciate all the design elements that went into that spectacle.
