4 Jun 2021 | The New York Times

Buildings With Sections That Seem to Hover in Midair

By Tim McKeough

Cantilevered towers help deal with space limitations in New York City. They start narrow at the street but expand as they rise, more lollipop than traditional wedding cake.

Ask a child to draw a picture of a skyscraper and they’ll probably sketch a familiar form: perhaps a skinny rectangle standing on its end, or a tapered block that culminates in a pointed spire. After all, for more than a century, that’s typically how tall buildings have been designed.

But in New York, where land is scarce and the streetscape is increasingly crowded, a growing number of residential projects are turning the conventional skyscraper on its head. By building with cantilevers, they start narrow at the street but expand as they rise, more lollipop than traditional wedding cake.

Despite the structural challenges inherent in making large parts of buildings seemingly hover in midair, there are many potential advantages to doing so, depending on the limitations of a building site. Sometimes, pushing more of a building’s allowable square footage up to higher floors by adding cantilevers is a way to create more apartments with better views and light.

Other times, when developers are limited by a height restriction, building sideways over a neighbor is the only way to maximize square footage as part of an air rights deal. In still other cases, it’s about sidestepping competing towers, creating more appealing space at ground level or simply realizing a design statement that can help a new project stand out from the crowd.

“Cantilevers offer a nice element of drama to the form of a building,” said Michael Kirchmann, an architect who is the founder and chief executive of the development company GDSNY, which recently completed the Emerson, an eight-unit condominium at 500 West 25th Street where the top floors cantilever toward the High Line. “A cantilever just adds to that dynamism and excitement people have in unraveling in their heads how a building stands up.”

While cantilevers might be thrilling to look at, they also offer real rewards for residents and developers in many cases. “Generally speaking, the further you get up into the building, the more valuable the space becomes,” Mr. Kirchmann said. “So, it’s not only an architectural thing, but it can become financially very beneficial for a project as well.”

Better Light and Outdoor Space
The cantilevered top of the Emerson doesn’t hang over a neighboring building — the 10-story building rises completely within its own zoning envelope. GDSNY created the cantilever by holding the western side of the building back from its neighbor, Mr. Kirchmann said, which provided a number of advantages. The space in between the two buildings allowed the firm to create a private outdoor terrace for every unit and add windows where there otherwise would have been solid wall along the lot line. The top floors, meanwhile, are boosted up higher than they would be without the cantilever, providing views of the High Line and Hudson River.

At 98 Front Street in Dumbo, Brooklyn, the architecture firm ODA designed a condo for Hope Street Capital with a multitude of cantilevers to provide more outdoor terraces and windows for more apartments. The building resembles an uneven composition of stacked cubes, where some boxes hang off others.

“The old way of building in cities is simply an extrusion of a floor plate, endlessly or until zoning stops us,” said Eran Chen, the founding principal of ODA. “It might be efficient and easy to construct, but ultimately is very limiting in terms of the most essential elements that I believe we’re looking for in our community and built environment.” Those elements include access to natural light and air, as well as opportunities for casual encounters with our neighbors, Mr. Chen said, who imagines residents at 98 Front might greet each other from their terraces.

Breaking from a building that goes straight up resulted in some challenges, said Sha Dinour, a partner at Hope Street Capital and the president of Triumph Property Group. “It’s certainly more complicated to build,” he said, noting that ODA’s design resulted in nearly a hundred different layouts for the building’s 165 apartments, and that plumbing, electrical, waterproofing and insulation all needed to track the building’s shifting shape.

With so many different layouts, “the selling process was difficult,” he added, because apartment hunters had so many units to choose from (the building is more than 60 percent sold). The upside for buyers, however, is that “people tend to really have unique, one-of-a-kind homes that don’t repeat themselves.”

Maximizing Floor Area
The size of buildings in New York is controlled, in part, by something called the floor area ratio — the amount of total buildable floor area allowed per square foot of the building lot. When developers want to build bigger than their lot size allows, one option is to purchase air rights, also known as development rights, from an underdeveloped neighboring lot.

In many cases, that extra floor area is simply stacked on top of a proposed development, resulting in a taller tower. But some zoning districts place height limits on buildings, which can create situations where the only way to use all of the air rights available from a neighbor is to build sideways in the sky instead of up.

“When I typically would see a cantilever is when I’m in a zone that has a height limit,” said Daniel H. Braff, a zoning and land use attorney at Sahn Ward.

“I can’t utilize all of your floor area within my building envelope,” he explained, imagining a developer’s perspective. “I want to buy all this floor area and build a larger building, but I can’t go up. I’m capped. So the only way to utilize your floor area in my new building is to cantilever over your building.”

That wrangling around zoning envelopes can lead to some dramatic looking structures. At 251 West 91st Street, for instance, ODA has designed a 20-story gravity-defying tower named Era, a new condo project from Adam America Real Estate and Northlink Capital that is currently under construction.

Only 50 feet wide at the ground where it faces Broadway, the limestone-clad building expands north in the sky in a series of cantilevers over a SoulCycle and Equinox gym, stretching out an additional 45 feet by the top, nearly doubling its width beneath a height limit of 210 feet.

“It’s really a piece of art or a statue that is going to reveal itself in the months to come,” said Tomer Yogev, the head of development at Adam America Real Estate. All that horizontal space on the roof provided extra space for shared amenities, Mr. Yogev said, including an outdoor pool.

Eleven Hancock, a 12-story condo nearing completion at 11 Hancock Place in Harlem, which was designed by Isaac & Stern Architects for Nortco Development, achieves a similar sense of levitation with a 22-foot-long cantilever over a CityMD on West 125th Street, under a 125-foot height limit.

“In New York City, you’re limited by zoning and the box, so with extra air rights the only way to go was sideways,” said Ralph Kowalczyk, a partner at Isaac & Stern.

Such mushrooming growth can easily lead to awkward looking buildings, Mr. Kowalczyk noted, so the architects tried to break up the structure’s bulk by switching from zinc-colored metal to copper-colored metal from the sixth through eighth floors, where the building begins to cantilever, and introducing strong horizontal lines that make that section look more like a supporting plinth. “You have to deal with the appearance and try to rebalance and make sure the building still looks shapely and nice, and has a form and expression,” Mr. Kowalczyk said.

Capturing Views and Working the Site
One of the most hair-raising new cantilevered buildings in New York is Central Park Tower at 217 West 57th Street. The 1,550-foot-tall tower, designed by Adrian Smith + Gordon Gill Architecture for Extell and Shanghai Municipal Investment, is billed as the tallest residential tower in the world — a feat of engineering even without a cantilever.

Nevertheless, about 290 feet up from the street, the building stretches 30 feet out to the east, over the Art Students League of New York. It would have been possible to position the whole tower further west instead, said the architect Gordon Gill, but shifting the core of the building to the eastern side of the lot and adding the cantilever made sense for a number of reasons.

“In the context of the city, we were now able to look around, and look past, the building that’s just north of us,” Mr. Gill said, referring to 220 Central Park South, “and get these fantastic views.” Without the shift, many of the apartments would have had their Central Park views obscured.

But Mr. Gill said another important consideration was creating an appealing retail space for Nordstrom at street level. “They’re about 300,000 square feet of retail and we knew that the best possible retail should not be encumbered by a core,” he said. Shifting the core of the building — a structural backbone that contains elevators, stairs and plumbing and electrical lines — to one side, he said, effectively created an open floor plan for the store.

At Greenpoint Landing, Block D, in Brooklyn, the architecture firm OMA similarly didn’t have to add cantilevers to one of the condo’s two towers to maximize the project’s floor area for Brookfield Properties and Park Tower Group. They could have gone straight up. But by adding a series of stepped cantilevers to one 40-story tower, and cutting the other, 30-story tower back in the opposite direction, they aimed to take advantage of both a new waterfront esplanade and views across the East River to Manhattan.

“The result is almost like a single block that’s split into two,” said Jason Long, a partner at OMA. “By extending the bottom of the lower tower, we accentuate the park frontage that it has. And then for the taller tower, you get the city views.” At the top, the taller tower extends 48 feet out from its base on one side, creating lots of additional windows that stare straight at Manhattan.

The design also allowed the firm to increase the space between the towers beyond what would have otherwise been possible, Mr. Long said, from 40 to 60 feet, making way for amenity spaces and a lobby that are threaded between them.

“It’s not so much that we’re claiming space from someone else,” Mr. Long said, “as just trying to organize this whole composition in a way that’s most advantageous.”

The architecture firm FXCollaborative had a similar goal when it designed Jolie, a condo developed by Trinity Place Holdings at 77 Greenwich Street in the Financial District that is nearing completion.

“We didn’t really have a height limitation, but there is the practicality of how high you want to build and how skinny you want to build,” said Matthew Messinger, the president and chief executive of Trinity Place Holdings. “This building actually tops out at a little over 500 feet, but offers extremely competitive, attractive views,” he said. “We didn’t have to build a total toothpick of a building.”

The team achieved its objective by adding a series of modest cantilevers totaling 10 feet over the landmark Dickey House to the south (which Trinity Place Holdings restored as part of a new home for Public School 150), as well as introducing a pleated facade that directs views out over the southern tip of Manhattan. “All the views were to the southwest,” said Dan Kaplan, a senior partner at FXCollaborative, “to the harbor, to the water, to the Battery itself, to the Statue of Liberty.”

Building larger floor plates at the top of the building also resulted in more floor area exactly where the developer wanted it — in larger, more expensive apartments. “It did really make the layouts at the top much better to step over the Dickey house,” Mr. Kaplan said.

A Way to Grow in a Crowded City
Confined by zoning regulations, architects and developers are using cantilevers as a creative way to gain every possible advantage in an increasingly crowded cityscape, even if it involves structural gymnastics.

By making leftover airspace habitable, cantilevers can help overcome a building site’s limitations, which makes them uniquely valuable in a city like New York where there is little vacant land left. It most cases, it’s not just about making an architectural statement — it’s about finding a way to build more, and more compelling, homes.

“What’s really great about New York City urbanism is there’s a set of rules and everybody sort of figures out a way to interpret the rules a little bit differently,” Mr. Kaplan said. “They find their clever way to work within the rules to create the skyline.”