The exterior of Cape Town’s grain silo building will be refitted with pillow-shaped glass panels; at night they are meant to glow like a lantern, attracting visitors to the waterfront. Heatherwick Studio
A historic Cape Town grain silo building is reimagined as a contemporary art museum.
May 6, 2014—Situated between the Atlantic Ocean and majestic Table Mountain, Cape Town’s Victoria & Albert (V&A) Waterfront is one of the city’s major attractions—a collection of marinas, markets, museums, and shops that’s visited by as many as 100,000 people a day.
Rising from the center of the waterfront is the city’s historic grain silo building, a 187 ft tall hulk that was built in 1927. The structure contains 42 silos that stand more than 100 ft tall and are more than 16 ft in diameter. “Once the tallest building in Cape Town, the silos were at the heart of the operational life of the city’s waterfront dock, facilitating the collection, sorting, storing, and the exportation of much of the country’s grain for the better part of the last century,” said David Green, the chief executive officer of the private investment firm, V&A Waterfront Holdings, the V&A Waterfront’s developer, in written responses to questions from Civil Engineering online.
Since the grain silo was decommissioned in August 2001 there has been growing interest in its fate. The question about the silo building has always been how to retain its historic fabric while reimagining the interior space for 21st-century use. The answer, it turns out, is to convert the hulking concrete structure into a lanternlike home for a new contemporary art museum dedicated to the African diaspora.
The project, says Mat Cash, the head of projects development for Heatherwick Studio, the London-based architecture firm handling the renovation, has had a long gestation period, dating back to a talk that the firm’s founder, Thomas Heatherwick, gave at a Design Indaba (think ‘TED talk’) in Cape Town in 2005. Heatherwick and Design Indaba’s founder, Ravi Naidoo, found themselves walking around the empty building that commanded the waterfront. They realized they were dealing with, as Cash notes, “an extraordinary building that’s sitting right in the middle of this beautiful harbor and nobody knows what to do with it.”
But conversations stalled until a few years ago, when Growthpoint Properties Limited, one of the largest developers in South Africa, acquired the property. After the firm hosted a series of charrettes in Cape Town, Heatherwick was commissioned to conduct a three-month study to investigate how the building could be reused. Early on, stakeholders knew the building would have to have a significant public function, perhaps as a museum or gallery. And whatever new use the silo was put to, any renovation would have to work with, and not against, the historic structure and its unique program.
The central atrium of the new museum will be carved from the
former grain silos, creating what designers hope is a cathedrallike
space. Heatherwick Studio
The grain silo is really two buildings separated by a narrow gap: the “tubey” collection of silos on the east, as Cash describes it, and a taller, square-shaped elevator tower to the west. When the silo was in operation, trains would enter beneath a track shed on the western side and drop grain to the bottom of the elevator building. The grain would be lifted up to the top of the building, where it would be cleaned and sorted, then dropped into storage bins about 5 m wide—either square-shaped bins in the elevator tower itself or in circular bins on the eastern annex. When boats arrived, the grain would fall to the basement of the complex, where a conveyer belt would transport it out to the ships waiting at the waterfront.
Recently the silo building found a tenant, the Zeitz Museum of Contemporary Art Africa (MOCAA). Founded by Jochen Zetiz—formerly the chief executive officer of the German sports shoe company Puma SE—the museum is being billed as the first major museum of contemporary art on the continent. It will occupy 102,000 sq ft in the silo, spread across nine floors. In addition to the museum’s 80 planned galleries, the Zeitz MOCAA will feature a rooftop sculpture garden, advanced storage and preservation facilities, bookstores, and dining spaces.
Even before Zeitz came on board, Heatherwick designers were wrestling with the fundamental challenge of the project: how to make the place suitable to a new use without stripping away the building’s industrial soul. The building was clearly no longer viable for industrial use—it was, Cash notes, “a big machine” for processing and storing grain. Structurally, it combined many systems; for instance, on the upper level of the elevator tower, where the sorting and cleaning machines were situated, “rather than slipform[ed] storage bins, the structure was a mixture of steel and in situ concrete.” Removing the machinery revealed the structural grid of the upper portion of the elevator tower. (Some key examples of the machinery will be preserved in the renovation.)
One of the firm’s most critical tasks was channeling light into the imposing structure. The designers didn’t want to cut a lot of holes into the exterior of the building, not only because of the impact to the building’s identity but also because natural light might damage the artwork that they knew might one day be displayed there.
On the eastern side, the windows and penetrations Heatherwick experimented with wound up resembling slits, giving the building an odd castlelike appearance. The approach, says Cash, was “fighting what the building was. It didn’t feel true to the history or integrity of that.”
At first Heatherwick planned to open the upper levels to natural light by inserting curved glass windows in the wall grid. But the proportions were off—it made the building look too much like an office tower. So designers hit on another idea. Inspired by glassblowers in Florence, where some artisans blow glass through chicken mesh, designers envisioned the windows as if they were glass panels seeping through the mesh of the building itself. In this case glass panels will pillow outward, as if being gently inflated from inside the building, and protrude “through” the existing grid of the facade. These windows will glow gently like a lantern, attracting people to the building and the waterfront.
But the real challenge to the renovation was on the interior. Except for the upper levels of the elevator tower, there was no large open space within the building—it wasn’t designed, after all, to have impressive interior volumes for people to stroll through. As Thomas Heatherwick put it in a statement issued by V&A Waterfront, “We could either fight a building made of concrete tubes or enjoy its tubeyness.”
Cape Town’s historic grain silo building, which dates to 1921, will
be transformed into the home of Africa’s largest contemporary art
museum. Heatherwick Studio
The solution was to carve a central atrium from within the eight center silos, creating what the firm describes as a “cathedral-like central atrium filled with light from a glass roof.” Gallery spaces will be carved out of the silos as well. A glass roof will be placed overhead. With models and 3-D visualization tools, the architects investigated different geometries, but found that horizontal and vertical cuts through the space weren’t terribly interesting; they created charmless flat edges. But when they started experimenting with slicing through the space at an angle, they created more dramatic, elongated ellipses. The angles were not arbitrary: the firm scanned a single grain of maize and enlarged it and based the angled cuts on that.
Cash says that when the building was in use, fireman poles enabled workers to quickly slide down from the top of the structure to the bottom, while the grain elevator had leather straps attached to it so workers could hold on for the ride back up. The new building will have cylindrical lifts and a spiral staircase through central atrium. The idea is to replace the ballet of grain moving through the building with people. “So it becomes quite an interesting play, and it also tells the story of what was there before,” says Cash.
Structurally, designers are forming a big arch with their cuts. Cash says the grain silo tubes, designed to hold hundreds of tons of grain, “are basically very robust. The compressive forces worked very well structurally. Now that they’re taking stuff out, the trick is to take those loads down different paths.” The solution is to resleeve the silo tubes. New tubes will be cast inside the existing tubes, so the existing tubes will form a type of formwork, he says. Casting the new tubes will form an arch that will take loads from the top down to the edges.
The central atrium space will be naturally ventilated. Motorized vents will be located within the curtainwall facade on the ground floor for air intake, while the exhaust will occur through the top of the bins on the perimeter of the roof.
The outside of the building has experienced spalling. Removing the plaster and jet-blasting has exposed the aggregate of original concrete, which will be resealed with hydrophobic impregnation.
Work on the project, which is expected to provide a jolt to the city’s creative economy, is expected to be complete in 2016. “This is a vibrant industry that has value,” says Green, “and our decision is a reflection of our confidence in this sector to make a difference in the lives of not only the artists but also our visitors and the broader South African community.”