From its inception, the basic structural tendency of mainline, 20th-century Modernism was a simple one. Whether you take as a starting point Le Corbusier’s ultrareductive Maison Domino, or Meyer and Gropius’s Fagus-Werk, or the more apparently complex tectonics of Frank Lloyd Wright’s Robie House, the pattern is the same: a stack of floor plates upheld by vertical supports (preferably of steel), with a disengaged skin (preferably of glass). Especially in taller buildings, the stolid, rectilinear skeleton was in the ascendant for decades.
There were always, of course, departures—formal excursions, breakaway movements, the work of structural genies near the outermost limits of the field. But over the last several years, something new has been under way. The accumulated results of those outsider experiments have coalesced into a structural type that has wedged its way into practice, and that is now having its moment. This is the moment of diagrid.
“I think the one person that really popularized it in the last 20 years or so has been Norman Foster,” observes engineer Guy Nordenson, founding principal of Guy Nordenson and Associates. In 2001, Foster, Hon. FAIA, and his firm started work on two high-profile projects, in London and New York, both sporting a unique diamond patina running up their glassy façades—the Swiss Re building at 30 St. Mary Axe, and the Hearst Tower at W. 57th St. and Eighth Avenue. They appear remarkably different in silhouette: the former like a slender torpedo, earning it its nickname, the Gherkin; the latter, a four-square ziggurat, cinching in every several stories. But the same system, expressed in the same pattern of triangular external struts, gave each its beguiling effect, one that seemed to promise a new kind of structural clarity in tall buildings.
Together, they marked the watershed for diagrid. Since 2003, the telltale diamond pattern has graced a host of large-scale projects around the world. A biggest-hits compilation would have to include OMA’s Seattle Public Library and CCTV Building in Beijing; Herzog & de Meuron’s Prada store in Tokyo; RMJM’s Capital Gate in Abu Dhabi, United Arab Emirates; and Zaha Hadid’s Zaragoza Bridge Pavilion in Spain.
The fundamental operation of diagrid, and its root appeal for architects, is plain enough. Yoram Eilon, vice president of engineering firm WSP Cantor Seinuk, was project manager on Foster’s Hearst Tower, and he distills diagrid to its essential physics: “A series of triangles that combine gravity and lateral support into one, making the building stiff, efficient, and lighter than a traditional high-rise.” The portmanteau says it all—“diagrid,” from “diagonal grid.” The crisscrossing steel members, connected at specially jointed nodes, are mutually reinforcing: they create an integral network across a building surface that braces against the floors, the wind, and the members above. With this exoskeleton in place, the designer can cut down on internal supports, saving on space and building materials, allowing naturally broad apertures, and providing greater flexibility for systems installations.
Simple in outline, the morphological potential of diagrid is almost endless. In London, artist Anish Kapoor has been at work on a monumental sculpture, called the ArcelorMittal Orbit, for the city’s upcoming Olympic Games, developed in collaboration with Cecil Balmond, the once director of engineering giant Arup. Intended to stand outside the main 2012 stadium, the Orbit is a twisted knot of diagrid masts, curled into a self-supporting roller coaster some 375 feet high.
In Seoul, South Korea, Skidmore, Owings & Merrill (SOM)’s Lotte Super Tower, a nearly 2,000-foot-tall office building that incorporates three different geometrical masses, begins on the ground floor as a square, rises to a triangle, and culminates at the top as a circle. Says SOM’s Mustafa Abadan, FAIA, “Diagrid allowed that to happen, providing an architectural enclosure made of straight planes”—a consistent sleeve that could be pulled over the ensemble, stretching to follow the contours of the building’s different forms.
The stretching takes place in diagrid’s diamonds, which open and close, widen and flatten, to accommodate the various twists and turns in the overall structure, as well as its shifting loads. That can make for vexing logistics. The new opera house in Guangzhou, China, from Zaha Hadid Architects uses a lattice frame of striking variability, its irregular grid requiring a series of fitted joints that had to be sand-cast, as Hadid, Hon. FAIA, notes, “as in a medieval bell foundry.”
The recent profusion of diagrid has seen it appear as everything from an integral structural system for large buildings to a freestanding screen. But in every instance, the identifying trait, the underlying module of diagrid, is the triangle. In that form lies both diagrid’s structural strength and its historical origins. “Nature’s own system of coordination [is] based on triangles,” said visionary engineer and designer R. Buckminster Fuller: provided its joints are strong enough, the triangle does not collapse under pressure applied to any one point, as each side is buttressed by its neighbors. Upon this principle, Fuller built an entire worldview, along with scores of proposals for buildings that elaborated his triangular concept into buildings of all kinds, notably his famous tensegrity and geodesic constructions.
Fuller was foremost among those ingenious tinkerers testing the limits of modern structure, and he stands as the most immediate forefather to the current wave of diagrid buildings. Norman Foster worked with Fuller in the last decade of the engineer’s life, and has described him as having “a profound influence on my own work and thinking.” Nordenson is another product of Bucky’s office, and cites him as a prime source of the diagrid trend, as does Arup’s Dominic Munro, structural engineer on the Swiss Re project. Munro’s firm has helped shape a number of recent diagrid-type projects, and around the office, he says, “The reference that we usually use is ‘back to Fuller.’ ”
But there are other antecedents, too, as Munro is quick to point out. “What diagrid does is take the structure of a continuous shell, which works in any direction, and pair it with the constructability of the discrete element, the beam-and-stick approach. It’s a discrete-ized shell.” In a similar key, SOM partner William Baker has cited the work of 19th-century Russian prodigy Vladimir Shukhov, a mathematician and scientist who pioneered lightweight hyperboloids and radical tensile structures. There are still other innovators whose insights into tall-building construction have contributed to the present diagrid craze (Fazlur Khan’s X-braced John Hancock Center is a major milestone), but the idea of diagrid as a simplified take on continuous concrete or fabric structures connects its newfound popularity to a distinct tradition: a plastic, expressive strain of Modernism, one that runs through figures such as Felix Candela and Eero Saarinen, and that links up neatly with the heady ambitions of today’s international designers.
Certainly, the endless sequence of new and increasingly complex geometries that has emerged from the design profession in the last two decades has been a driving force in the growing popularity of diagrid. As we’ve moved outside the Modernist box, diagrid has rushed in to keep the roof over our heads. Sometimes literally: Asymptote Architecture’s Yas Hotel in Abu Dhabi features a vast diagrid screen that vaults up and over the main body of the hotel. Firm principal Hani Rashid connects the use of diagrid in the project to the formal possibilities unleashed by digital design techniques. “There are these remarkable possibilities to optimize and parametrically control … that we didn’t have even five or six years ago,” the designer says.
In fact, the opening salvo in contemporary architecture’s digital revolution features, if rather discreetly, a diagrid structure. Frank Gehry’s Guggenheim Museum in Bilbao, Spain, is famed for its computer-molded, curvilinear metal cladding. But lift up the lid, notes Guy Nordenson, and it’s “a kind of diagrid, a triangulated surface back from the skin. It’s all made up of triangles. It’s just not the kind of filigree that people associate with diagrid.”
But what “people associate with diagrid” is an essential part of the equation, since it’s the forthright presentation of the grid—not the obscuring of it—that seems to have caught on so dramatically with the profession of late. “It’s the image of sustainability,” opines Craig Schwitter, managing director for design consultant Buro Happold. “It helps form an understanding of what environmentally sensitive buildings could look like.” Schwitter’s firm has been involved with a series of projects that have included the “mapping” system of diagrid, and he sees it as a kind of advertisement for the material thrift, and the attendant green benefits, of the buildings that deploy it. “That’s where a building like Hearst really sings,” Schwitter says. “It looks energy efficient and it is.”
That’s true. On its completion, the Hearst Tower became the first in New York City to merit LEED Gold certification for its exterior and interior fittings. Likewise the Gherkin, whose diagrid was born of Foster’s effort to create a sequence of skewed atria to allow for natural ventilation and light wells that could cut down on energy consumption: vertical columnar supports simply wouldn’t do the job. Not only that, but, as Dominc Munro of Arup explains, “The Swiss Reinsurance company’s business is global risk. They were amongst the first in the world to underwrite the potential risks of climate change.” For them, the building had to read “green,” and the legibility and openness of diagrid fit the bill exactly.
With all this, and the public accolades that so many diagrid buildings have attracted in the press, the prospective benefits of using the technique (where appropriate) seem to outweigh the obstacles of building in it. Rashid’s client initially balked at the notion of putting in place some 5,680 individual diamond shapes, but eventually saw the light, especially after “we got it done in under 14 months,” he says. And as the approach diffuses throughout the practice, it filters down to builders and fabricators, so that erection is getting easier and more efficient. Says WSP Cantor Seinuk’s Eilon, “If you built … [Hearst] now, you would save a lot more” on construction and material costs.
There is one additional factor, however, that may also account for the surge in diagrid designs over the last 10 years, though it’s a great deal harder to quantify. Norman Foster unveiled his initial proposal for his Manhattan tower to his clients on the morning of Sept. 11, 2001; three years later, it became the first large tower to break ground in New York after the attacks. In the initial proposals for the new World Trade Center, one of the most popular submissions—from the collective team of Allied Architects—made extensive use of diagrid, as did an early model for 1 World Trade Center, developed in consultation with Guy Nordenson. Even Foster’s Swiss Re is a building inextricably bound to the memory of violence: The former 30 St. Mary Axe was critically damaged in an IRA bombing in 1992.
There is a palpable coincidence between the sudden proliferation of this decidedly eye-catching, assertively articulated structural system, and the advent of our new age of anxiety. It may be only a coincidence, but it is an uncanny one. We live in an era in which the representation of structural strength takes on a deep moral resonance. Even in Asia or the Middle East, diagrid speaks a reassuring language of stability, a message qualified by its real physical economy and resilience. As Buro Happold’s Craig Schwitter puts it, “You can’t fool mother nature.” Diagrid looks like it should work, and it does.