The art of connection – San Francisco Museum of Modern Art

Norwegian architectural practice Snøhetta’s crinkly white extension to San Francisco Museum of Modern Art stands in stark contrast to the existing museum’s geometric form, but as Stephen Cousins discovers, there is more to this unusual architectural marriage than meets the eye.

Rising like a giant cliff face over the streets of San Francisco, the $305m extension to the San .Francisco Museum of Modern Art (SFMOMA) represents a radical departure from the original museum to which it is attached.

When it was opened in 1995, the museum was the first US building by renowned Swiss architect Mario Botta. Its robust, angular postmodern geometry and squat profile were initially greeted frostily by critics, but the building went on to become an iconic and familiar presence in the South of Market neighbourhood.

Snøhetta’s addition looms up behind the original and almost triples the amount of gallery space. Its elongated profile and striated white cladding contrast markedly with Botta’s flat red brick facade and oculus of zebra-striped granite, manifesting a unique and unmistakable presence in the city.

Dancing partners
But Snøhetta’s intention was never to copy Botta’s design, instead the firm wanted to create what it has described as a ‘dancing partner’ that complements the older building, while trying not to step on its toes.

Jon McNeal, project architect at Snøhetta told ADF:

“On the exterior, the buildings represent two different attitudes from two different times, they maintain their own distinct identities and don’t look like they are trying to merge into a single statement. On the interior, we wanted to create a relatively seamless experience so the spaces linking the buildings flow together enabling free movement and easy experience of the art.”

The 21,832 m² extension runs contiguously along the back of the existing building, it includes seven floors of gallery space capped by three levels for administration departments.

Entering the new Howard Street entrance, visitors ascend an amphitheatre staircase overlooking San Francisco-native sculptor Richard Serra’s epic 13-foot-high work, Sequence. A wide lobby stretching across the second floor creates an open connection between that space and the original building’s entrance, along Third Street.

Here, Botta’s huge sculptural staircase under the oculus has been removed, replaced by a much smaller staircase, also clad in maple. Aside from the galleries, there is a multipurpose performance space, two restaurants and a spacious third floor dedicated almost entirely to photography, plus terraces for viewing sculpture.

Ripples and fog
On the exterior, Snøhetta wanted to evoke a sense of both the local landscape and the collection of art housed inside. The longest (east) facade is covered by over 700 fibre-reinforced polymer panels which create an extended pattern of ripples mirroring the choppy waters of San Francisco Bay.

The facade undulates and bulges at its centre, reflecting the hilly topography of San Francisco and the clouds of white fog that occasionally roll off the hills, pushing between the high rise buildings as if cutting the city into slices.

This naturalistic approach is one Snøhetta has used before, notably for the glacier-like opera house in Oslo, where the firm was founded.

The sheer scale of the new wing was needed to exploit the influx of visitors and tourists to the South of Market district of the city. Back in 1995, when Botta’s building was erected, the neighbourhood was a rundown area, characterised by dilapidated buildings and little development. In the intervening 21 years, hotels, cafes, restaurants, shops, and other cultural buildings have sprung up, plus a large convention centre that pulls in millions of visitors from out of town each year.

McNeal comments on the expansion:

“It is an active cultural and tourist destination in a way that was never envisioned when the original building was constructed. The museum’s mission has changed too, it is no longer there just to develop and protect the art, but to make sure it is accessible to more people, which meant taking a very different approach to the street frontage.”

A dizzying total of 1,900 works went on display when the new museum opened, designed to show off the greatly expanded collection.

Large and opaque
As well as being physically large, the extension had to be very opaque to prevent sunlight from damaging the sensitive artwork inside and to meet strict sustainability requirements under California’s Building Energy Efficiency Standards, which discourage the use of extensively glazed facades in order to mitigate cooling requirements. The facade is punctured by just a few strip windows at locations where daylight and views don’t impinge on the artworks.

Snøhetta developed over 100 concept models for facade treatments in effort to identify one that would give the building a strong personality and make it more friendly to its neighbours.

“The idea for the ‘ripple-scape’ won out over other ideas because we saw that it would self-animate the building, compared to having a flat facade, or a repeat pattern, creating different shadows at different times of day as the sun moves around the site,” says McNeal.

More dynamism was introduced by curving the facade, vertically and from north to south around the centre, which increases the amount of shadow on the northern end and, by cutting off views along the length of the museum, helps break down its volume to a more human scale.

The bulging centre accommodates the vertical stair and lift circulation, minimising the need for corridors and hallways. This allowed the corners of the building to be pushed back from the street, to bring in more daylight and improve views.

Rather than clad the expansion with stone or precast concrete, which would increase weight and cost, Snøhetta worked with cladding contractor Enclos and facade manufacturer Kreysler and Associates to develop a lightweight substitute material option for the facade. Their solution is an elegant hybrid curtain wall system made up of FRP (fibre-reinforced polyester) cladding panels, almost all of them unique and malleable enough to hold the ripple design.

Each panel is around three eighths of an inch thick and comprises layers of FRP matting covered with a layer of epoxy and a surface layer of sand. The ripples, in combination with the epoxy, increase strength and stiffness, and a shallow return perpendicular to the surface attaches it back to an aluminium curtain wall sub-frame.

Standardising the facade
The sub-frame is similar to that used in office blocks, but instead of panes of glass, blank aluminium panels backed by a layer of insulation are installed between the mullions. The standardisation of the frame helped minimise costs as well as achieve the curving geometry in the FRP skin.

The sub-frame is composed of just two different types of panels; the vast majority are flat, around 5 ft 4 in wide and anywhere from 14 ft to 25 ft tall, depending on the floor to floor height. The rest are transition panels, creased from one corner to the other and designed to accommodate the curvature of the facade.

The combination of flat panels and transition panels made it possible to wrap the building with a seemingly continuous skin of FRP over the top. The FRP was attached to the aluminium curtain wall panels in Krysler’s factory, then delivered to site on a flatbed truck and hung straight on the building.

The modular design enabled easy installation by operatives stood on the edge of the floor slabs, with no need for scaffolding, or post-installation exterior sealants or gasketing.

“The extremely aggressive construction schedule and a very tight site meant there was little space or time to build scaffolding, so it was key for us and the contractor to develop the facade system the way we did,” says McNeal.

Whole lotta shakin’
Snøhetta’s dance partner analogy extends to the way the two buildings respond to one another in the event of an earthquake.

Each moves differently during tremors, due to the fact that Botta’s building is wider and more squat in shape, whereas the extension is thin and relatively tall. A physical gap between the two therefore had to be maintained to prevent damage to one another during a quake – wide enough to allow horizontal movement of 1 per cent of the building’s height above the ground.

Specialist joint covers were installed where the buildings connect to enable continuity of floor and wall surfaces. For example, special interior floor panels are designed to kick up during an earthquake, like a hinge on a door, enabling the concrete slabs underneath to move closer together. The same panels fall down onto the slab edges when the buildings move apart.

“It is very unusual to have a system like this installed in a building as tall as ours,” says McNeal. “The Botta building is over 100 ft tall, the surface geometry has lots of ins and outs, and different massing, and we had to develop a system to cover all those different conditions. There are about 50 different types of connections between the two.”

It’s another example of how the two buildings come together but simultaneously maintain a distinct separation. It’s an architectural marriage for certain, but is it a match made in heaven or the equivalent a bad blind date? Mario Botta’s last statement was that he would reserve judgement until he sees the new building in person.

In some ways it is understandable that he would have concerns, says McNeal:

“The original was his first and only building in the US and it is not a particularly old building, so he was sensitive to any modifications. What should not be lost in the media chatter is that we were able to build an extension because of the success of the original building and not in spite of it. Some people look at an addition as a knock to the original, but I always saw it as the opposite,” he concludes.