Herzog & de Meuron (H&dM) has developed something of a specialty at taking our tired old building tropes and finding new ways to interpret them. Now the Swiss architecture firm has turned this talent to the skyscraper. At 56 Leonard Street, an 820-foot-tall luxury condominium development that has begun construction in Tribeca, H&dM has turned its back on many of the inherent efficiencies of the highrise—namely repetitive floor plans—in favor of a design-intensive approach. Each of the building’s 57 floors is unique both in layout and profile. This was done in part to make each of the 145 apartments completely distinct, a selling point for the type of buyer capable of footing a bill that can range between $3.5 and $30 million. But it also created an envelope that entirely belies the standard extrusions we’ve grown accustomed to seeing ever since the Flatiron Building. The stacked floors create a seemingly random series of setbacks and overhangs, effecting plays of light and shadow across the surface that lend a mottled texture and sense of movement to the exterior.
A glance at these shifting floor plates might cause a shudder to go down the spine, as it looks as if some serious structural maneuvers must have been devised to make it all hold together. But the structural system is actually quite standard: a poured-in-place, reinforced concrete frame, consisting of shear walls in the core linked to perimeter columns by the floor slabs. The core slims halfway up the tower, going from six elevators to four, and there are two sections of structural outriggers on the mechanical floors, which increase the building’s rigidity and allow the columns to be arranged in such a way that increases flexibility in the floor layouts. The increased rigidity also makes possible the building’s startling cantilevers, which extend as much as 30 feet from the last vertical support. Most of the tower’s terraces (every unit has one) hang six feet off the slab edge, though the larger ones reach out as much as 10 to 12 feet.
But the most surprising story behind the structure lies in the lavish amount of energy spent on the design. The architects went through innumerable permutations of floor plate arrangements, bandying them back and forth with the structural engineer, Cantor Seinuk, to find an organization that met design goals while remaining within the realm of lateral stability. And while the shifting floor sizes didn’t completely fill the zoning envelope, with a width-to-height ratio of 1:13, the slim tower is at its structural maximum. As the building got taller throughout the two-year design process, it became necessary to install a slosh damper system in the mechanical penthouse. This is basically a large pool of water, 30 feet by 30 feet by 12 feet deep, which acts as a counterbalance against building sway by sloshing in the opposite direction as the wind.
As innovative as this approach to the skyscraper may be, in other aspects H&dM referenced classic high-rise design. The building is composed around the base, column, crown arrangement found in such old standbys as the Empire State, Woolworth, and Chrysler buildings. The tower also tapers gently as it ascends, eroding at the corners while the edges remain square, from 8,000 square feet at the ground floor down to roughly 6,000 square feet at the penthouse level. There is a typical hierarchical structure of amenities and residences: Above the lobby is a level of parking, topped by a lounge and spa, including a 75-foot pool. Four zones of residences comprise the column and crown sections, ranging in size from 1,030 square feet to 6,330 square feet: First there are four to five units per floor, then three, then two, and finally the crown is made up of eight full-floor residences.
The cladding system, however, swerves unexpectedly from the recent trend in highrise condos. Rather than go for look-at-me-world transparency with ultra-clear, low-iron glazing, the architects specified reflective glass for the window wall system. In part this choice was made to meet code insulation requirements, as the building is completely glass clad, but H&dM used it as a design boon by selecting a higher degree of reflectivity for the balcony doors than for the regular windows, creating sparks of light on the already shimmering surface and further animating the facade.
And then there’s the Anish Kapoor sculpture. Wrapped around the building’s corner columns at ground level, and protruding out onto Leonard and Church streets, the rounded, squished stainless-steel form was modeled on a balloon suffering under compression forces from above. In spite of its appearance, it accepts no structural load itself, but it does function as an important cultural barometer: Even in dollar-per-square-foot squeezed Manhattan, there’s still room for a bit of art—even if it’s not for its own sake.