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Modern Expansion Doubles Museum of Modern Art

Aerial view rendering of the San Francisco Museum of Modern Art
The San Francisco Museum of Modern Art (SFMOMA) has just broken ground on a new $365-million addition that included 143,000 sq ft of indoor and outdoor gallery space. The expansion will double the museum’s capacity for presenting art. MIR and Snøhetta

The San Francisco Museum of Modern Art will double its capacity with a sleek, narrow structure clad in stone, glass, and polymer-reinforced concrete.

June 25, 2013—Since the current home of the San Francisco Museum of Modern Art (SF MOMA) opened across from Yerba Buena Gardens, near downtown, in 1995, the museum’s collection has nearly doubled, to more than 29,000 works. To accommodate the need for more space, the museum has finally broken ground on a new that will double SF MOMA’s capacity for presenting art. First announced in April 2009, the $365-million project, designed by the New York office of Norwegian firm Snøhetta, will feature seven levels of new gallery and program spaces and three levels for administrative office. There will be 143,000 sq ft of indoor and outdoor gallery space and 41,000 sq ft of space free to the public.

Clad in hand cut stone, glass and polymer-reinforced concrete panels, the new addition strikes an ethereal counterpoint to the heavy, symmetrical façade of the current museum, which was designed by Swiss architect Mario Botta. On its dynamic eastern façade (which faces in the opposite direction from the Botta building) the new building will be scored with thin striations on its eastern façade, revealing long glass windows and shallow outdoor patios.

“One thing we were drawn to was San Francisco's distinctive topography and how long-distance views are unveiled as you move along the steep streets,” says Lara Kaufman, Snøhetta’s project manager, who responded to a series of questions via email. “The design makes the most of the vertical movement within the museum as a contrasting experience from the galleries, which are intimate, calm and regular. The network of stairs at the exterior wall link the galleries between floors, and from here you'll be able to see out into the city as well as experience the full scale of the addition, which is as long as a city block and quite tall. The diversity of spaces and experiences is something we think will keep visitors energized.”

The long and tall Snøhetta addition is a consequence of the building’s location, a narrow site behind the current building. “That’s where the site gets very interesting for us structurally, because it starts to dictate what we could and couldn’t do laterally for the building,” says Greg Briggs, P.E., S.E., LEED AP, M.ASCE, a senior principal of Seattle-based Magnusson Klemencic Associates, the project’s structural engineers.

 Exterior rendering of the San Francisco Museum of Modern Art, displaying hand cut stone, glass, and polymer-reinforced concrete panels

 The exterior of the new addition for SF MOMA will be clad in hand
cut stone, glass, and polymer-reinforced concrete panels.
MIR and Snøhetta

An extension at the rear of the Botta building will be removed to facilitate a smoother connection between the buildings. This will, says Kaufman, allow both buildings to share a “centralized and wide open connection.” While the buildings’ exteriors markedly differ, the visitor experience inside “will be one of moving fluidly between the two.”

The challenges were to join the buildings so that visitors could flow seamlessly between them while at the same time keeping the buildings structurally distinct. Given their different geometries—short and squat versus long and skinny—the structures would behave differently in a seismic event.

Similarly, Briggs had to figure out what to do with the 4.5 ft thick concrete mat foundation that rested under the original building and extended underneath more than half of the new site. He and his colleagues considered removing part of it—though they were concerned about the geotechnical impact on the foundation under the existing building. They also considered putting in really deep pile foundations to reach it. Instead they developed what he calls an “egg crate”—a series of concrete cross-walls put in the basement to help distribute the load from the new addition on to the existing mat. This will have an effect similar to a wide flange beam, spreading out the loads out evenly and making the foundation mat and the slab at the bottom of the new addition’s first floor act as one unit.

There were other challenges involved in joining the buildings together. The museum wanted more flexible gallery spaces, which meant spaces that were as column free as possible. The new addition needed floor-to-floor heights that would be appropriate for a modern museum; in the Botta building, these heights were only between 16 and 19 ft, and the plates were to be extended from the old building to the new. To squeeze out more depth in the new structure, engineers had to use shallower and heavier beams to increase the ceiling height as much as possible. Briggs adds that in areas where the public would gather for assembly or art viewing, portions of those floors were left open to provide a double-height space.

Seismically, the new addition will utilize a series of buckling restraining braces, which allows engineers to tune the building more easily than using normal steel diagonal braces. The BRBs — where steel is encased in a concrete tube, to prevent buckling — behave similarly in compression and tension forces, so they don’t have to be limited in design like a normal steel wide flange, which usually gets sized for compression.

While the new building’s thin shape very broadly suggests a cereal box turned on its side, its east façade is intriguingly faceted, almost like a delicately sliced iceberg. The east façade swells outward in a gentle bow, an effect Briggs calls the belly, which will house the museum’s city gallery, which will, he says, “provide communicating stairs between the gallery floors and opportunities for more natural daylight and views to the city.”

 Interior rendering of the San Francisco Museum of Modern Art, featuring a free public gallery space

 A free public gallery space will be located at the front of the
addition’s Howard Street entrance. Roman steps will allow visitors
to enjoy large scale art installations, as well as the street life
beyond. MIR and Snøhetta

While it lends energy and vitality to the form, the belly required the creation of a series of 25 ft cantilevers along the girder lines, which created certain structural challenges. In a typical building, he says, columns are along the edge of a building and the horizontal joints in the façade system need to provide movement for downward beam deflections between the façade panels at each floor. But the cantilevered girder could deflect up or down, like a diving board. Therefore, the joint in the façade system would have to be twice as large to accommodate both directions of movement, but this size joint was larger than what Snøhetta wanted in its design for this façade. So instead, along the cantilevered edge of the building, engineers used steel tubes to “link” the floors together to help minimize deflections and thus the joint size. “There’s a load sharing,” says Briggs, “so that we minimize the amount of movement between floors, so the joint size between the façade panels can be maintained.”

The ground floor entrance off Howard Street, on the south side of the structure, is planned as a free public space. The gallery is separated from the sidewalk by full height glass, “Inside the gallery, opposite the glass, Roman steps provide a place for people to gather, view the art and enjoy the street as a backdrop,” Kaufman notes. “Its tall ceilings and urban setting make it a unique site for large-scale installations.”

The museum also features a third floor vertical garden that can be seen from both the street and the atrium of the original museum. It can also be seen from all levels within the museum, she says, “making it a kind of orientation device for visitors.” The planting design, she adds, is based on local canyon understory landscapes found in the East Bay and Marin, which match the light and climate conditions of the garden. The water used to irrigate the garden is reclaimed from storm water and other recycled sources. Further, the building is expected to achieve LEED Gold certification, with an anticipated 15 percent reduction in energy costs, 30 percent reduction in water use and 20 percent reduction in wastewater generation.

The museum will close during the two and half years of construction and will reopen in 2016. The museum will present a series of traveling exhibitions around the Bay Area to connect its collection with the community during the construction.

In responding to a question about the façade, Kaufman notes that “the materials in combination offer a visual and tactile experience that operates at a variety of scales. When you approach the building up close, the rusticated stone and sculpted concrete panels appear each unique and contain the characteristic tiny details of natural materials. The deep surface texture of these will change during the course of a day depending on the location of the sun, producing a different pattern at the larger scale of the building itself. So though the building is large, the materials lend it warmth and animated surfaces that connect it to the larger environment.”

As Kaufman puts it, as a cultural building the addition “was never intended to fade into the background. But it plays well with others.”



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