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432 Park Avenue Credit: DBOX via Macklowe Properties 432 Park Avenue Credit: DBOX via Macklowe Properties
The city’s skyline is increasingly punctuated by residential towers that are not only high but ultra-high. Take, for example, 432 Park Avenue, which soars 1396 feet. But like many of the city’s highest residential towers, 432 Park isn’t necessarily home to more high-rise residents than other buildings. In fact, about a quarter of its 88 floors don’t have any residential units at all. So, what’s actually going on inside 432 Park and many of the city’s other new ultra-tall buildings?


While there is some truth to the fact that many of the city’s tallest buildings are home to empty residences, including those that have been bought up by foreign investors, if these buildings appear largely empty, absent owners aren’t entirely to blame. The real problem may be a zoning loophole that permits developers to fill multiple floors with mechanical equipment without officially counting the floors as part of the building. While this is good news for developers who can charge a premium for units on higher floors, these ultra-high buildings have recently come under attack. Indeed, if city planners are successful, developers will soon no longer be able to take advantage of what is commonly known as the “mechanical void” loophole.

Illustration of an

Closing The “Mechanical Void” Loophole


As detailed in a study released by the Department of City Planning in February 2019, under current zoning regulations, mechanical floor spaces can be excluded from zoning floor area calculations, and “there are no explicit height limits on these spaces." As a result, in recent years, some developments have exploited the loophole to build increasingly tall buildings with a higher percentage of upper-story residential units. While this practice isn’t out of compliance with local bylaws, it is not exactly in keeping with the norm. In most cases, there is a mechanical floor at a lower level, generally between non-residential and residential floors, and in taller buildings, there is generally an additional mechanical floor every 20 stories or so.

In May 2019, the New York City Council overwhelmingly voted in favor of a citywide text amendment to cap mechanical spaces at 30 feet before they cut into a building’s allowable footprint. The new amendment also discouraged the clustering of void spaces in a way that would pad buildings’ heights, and mixed-use buildings would be subject to the same limit.

Preservationists thought the new measures didn’t go far enough, and developers found them too restrictive, but lawmakers hailed it as a strong start. Council Member Ben Kallos, who represents much of Midtown East and the Upper East Side, said, "By strengthening and passing the proposal to limit the height of mechanical voids to 25 feet, we are taking a significant step forward toward stopping developers from getting around the zoning to give billionaires views instead of building affordable housing for New Yorkers. This is only a start."
Manhattan Borough President Gale Brewer has also emerged as a vocal opponent of the mechanical void loophole. As she said in an interview, "All they do is drive up the height of the building so that the owners can get a better price for the condos at the top." She lobbied for the text amendment, tweeting, "It's about time!" when it passed.

Recent Developments

When the new amendment was adopted, some thought 50 West 66th Street, a soaring new condominium developed by Extell, would be grandfathered in if the foundations were complete. But last week, State Supreme Court Judge Arthur Engoron ruled that the building violated the zoning laws by proposing “gargantuan mechanical spaces.” The proposed mechanical floors would have measured nearly 200 feet high, or about one-fourth of the building’s total height. Judge Engoron compared this towering empty space in the building to “having a frankfurter in the middle of your hamburger,” and killed the permits. Extell plans to contest the decision, but local activists were heartened by the news.


50-West-66th-Street-01 Rendering of 50 West 66th Street via Binyan Studios/Snohetta
On the Upper East Side, a similar battle played out at 249 East 62nd Street. The design by Rafael Vinoly Architects called for an octagonal structural core that would prop up the units and grant them extraordinary skyline and Central Park views. Neighbors expressed concern about the height of the "building on stilts" and its massive void, but its exposure to the open air may qualify it as outdoor space and exempt it from the new guidelines. The building was put on hold in March 2019 due to fire safety concerns, but it remains to be seen how the new measures will affect the project.

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Contributing Writer Cait Etherington Cait Etherington has over twenty years of experience working as a journalist and communications consultant. Her articles and reviews have been published in newspapers and magazines across the United States and internationally. An experienced financial writer, Cait is committed to exposing the human side of stories about contemporary business, banking and workplace relations. She also enjoys writing about trends, lifestyles and real estate in New York City where she lives with her family in a cozy apartment on the twentieth floor of a Manhattan high rise.