The Empire State Building, the Art Deco Chrysler Building, the super-tall One World Trade Center. New York City is home to some of the world’s most iconic skyscrapers.
But the buildings entering its famous skyline today are doing something unusual. They’re getting skinnier.
Take 111W57 on 111 West 57th Street. Upon completion in 2019, the 1,428-foot-tall (435-meter-tall) building in Midtown Manhattan will not only offer unobstructed views of Central Park, it will also be the slenderest skyscraper in the world, with a width-to-height ratio of 1:24.
Russia, meanwhile, is building its first supertall skinny skyscraper also in Midtown. Moscow-based architectural firm Meganom’s “shelves in the air” will top out at 1,010 feet (308 meters) at 262 Fifth Avenue and boast a slenderness ratio of 1:20.
Both buildings are part of a tribe of slender climbers sticking their skinny necks into the city’s architectural conversation.
What is a slender skyscraper?
Slenderness is not in the eye of the beholder when it comes to skyscrapers, at least. In this field, it is a technical engineering term. Whether it can be applied to a building is determined by the structure’s base width to height ratio, according to Carol Willis, an architectural historian and founder of the Skyscraper Museum in New York City.
“Structural engineers generally consider skyscrapers with a minimum 1:10 or 1:12 ratio to be slender,” Willis says.
In 2013/2014, the Skyscraper Museum museum presented its “Sky High & the Logic of Luxury” exhibition, documenting the rise of skinny structures in Manhattan. Slender buildings featured in the show included the 1,396-foot-tall (425.5-meter-tall) 432 Park Avenue; One57 aka “The Billionaire Building;” and the distinctive “stacked homes” 56 Leonard tower.
“New York’s slender buildings are unique as a development in skyscraper history – they’re different to simply tall buildings,” Willis says, adding that when deciding which skyscrapers to include in the show her team “accepted the slenderness ratios provided by their engineers.”
Determining a building’s slenderness ratio is often not a precise science, she cautioned: “Exact slenderness ratios are difficult to calculate because the bases and shafts are often very different widths as the buildings rise.”
Why slim down?
So when did developers start slimming down their skyscrapers – and why?
Willis says the “engineering and development strategies of slenderness were first seen in around 2007.” She pinpoints luxury residential condominiums One Madison Park, on Broadway and Park Avenue, and Sky House, between Fifth Avenue and Madison Avenue, as the first “slenders” to have cropped up in New York.
Complex zoning laws in the city were a motivating factor, Willis explains. While such regulations restrict the amount of land that can be built on within an area, a loophole allows for the transference of “air rights” from one plot to another. So developers could buy a small parcel of land, then buy air rights from adjacent plots and stack these to gain permission to build a tall tower. For example, if an existing building is shorter than its maximum allowed height then the developer of a new adjacent property could purchase the unused air rights, and stack them to the air rights of their existing plot – such a transaction is called a “zoning lot merger.”
Technological advancements also contributed to the rise of the skinnies.
“Over the past decade, advances in materials and engineering have made building ‘supertalls’ possible, specifically those with smaller footprints,” says Jonathan Miller, president and CEO of New York real estate consultancy Miller Samuel. Towers between 980 feet (300 meters) and 2,000 feet (600 meters) high fall into the “supertall” category.
Standing out from the crowd
While developers typically strive primarily for return on investment, they often also want to create a structure unique enough to get the market’s attention, says Miller. Slender designs, which come in all shapes and sizes, tick that box.