At 1,070 ft, the Transbay Transit Tower will be the tallest building in San Francisco upon its expected completion in 2015. © Pelli Clarke Pelli Architects
An office tower that is being constructed in coordination with the city’s new transit center will become the tallest building in San Francisco.
June 25, 2013—The San Francisco building code has long restricted the height of buildings, resulting in a relatively expressionless skyline because all of the high-rises are roughly the same height. But that is about to change with the construction of a stunning new 1,070 ft tall office tower that will become the city’s tallest building, surpassing the 853 ft tall Transamerica Pyramid.
The Transbay Transit Tower is being constructed on Mission Street, adjacent to the highly anticipated Transbay Transit Center, a regional transit hub that is being billed as the “Grand Central Station of the West,” in the city’s downtown. (See “Multimodal Mass Transit Center to Connect California Bay Area Counties,” in Civil Engineering, September 2010.) In 2006 the Transbay Joint Powers Authority, a collaboration of Bay Area government and transportation agencies, held a 10-month-long international design and development competition for both the tower and center. Money from the sale of the land on which the tower is being built is helping fund the transit center.
After short-listing four design and development teams, the authority awarded the joint project to the team of Pelli Clarke Pelli Architects, a design firm headquartered in New Haven, Connecticut, and Hines, a real estate development firm headquartered in Houston. While the competition was judged primarily on the basis of the transit center design, the tower configuration was also important. “We proposed a tower that we knew was going to satisfy and actually delight the people of San Francisco but also a tower that our direct client would be happy with,” says Cesar Pelli, FAIA, RIBA, a founding principal of Pelli Clarke Pelli Architects. “That is a tower that had to be efficient, that they could lease, and that they could build reasonably well.” Hines has since partnered with Boston Properties, a real estate development firm headquartered in Boston, to develop the project.
City planners granted special permission to allow the tower to exceed the prescribed height limit. The tower will have 61 stories crowned by an extended facade, rising nearly 150 ft above the roofline to conceal the rooftop mechanical systems. A vertical facet in the crown will be illuminated at night, calling attention to the tower against the dark sky. “San Francisco has set up a maximum height, and they suddenly realized that everyone was building to the maximum height, so they have ended up with a city with a flat top, with no charm, which is very anti-San Francisco in many ways,” Pelli says. “So this was an attempt from the city to regain a charming, more special silhouette.” Magnusson Klemencic Associates, an engineering firm headquartered in Seattle, is the structural engineer for the project.
The tower will be visible for miles across the Bay Area, so a great deal of thought went into its shape and impact on the skyline. “The most important thing for me is that this is a very beautiful form—very, very carefully proportioned,” Pelli says. The tower will take the form of an obelisk, slightly rounded corners and tapered walls accentuating its elegant appearance. “It’s a very soft, gentle square that goes straight up probably about 800 feet, and then it starts tapering to be 1,070 feet high to its very tip,” Pelli explains. At the corners, “the curved glass catches the [light] and makes the tower look even thinner than it is.”
From top to bottom, the tower will be clad in clear high-efficiency glass supported by a grid of vertical and horizontal mullions. The mullions will be painted a hue developed by Pelli Clarke Pelli Architects known as silver pale, which recalls the color of a pearl. “It will be very light white with a bit of silver, a bit of reflectivity to it,” Pelli says. The glass and mullions combination will give the tower a sense of transparency. “It will be a very San Franciscan tower,” Pelli says. “It will be very fresh.”
A wide bridge will connect to the tower’s fifth level to the transit center’s 5.4-acre public rooftop park, which will include grassy areas, indigenous plants, trees, water features, and an amphitheater. At that level, the tower will house food and beverage facilities as well as some retail space. “We realized that [connecting the park to the tower] would have great potential because it would be full of people who will be able to go to have a drink or a bite to eat or to have a cup of coffee with a friend,” Pelli says. “It will also be delightful for the people in the tower to walk directly onto the park.” Designed to achieve at least a gold level certification in the U.S. Green Building Council’s Leadership in Energy and Environmental Design rating system, the tower will have several sustainable features, including a ventilation system that will push fresh air into every floor of the building.
The tower is being constructed in coordination with the transit center and both structures are tentatively expected to be complete by the end of 2015. At that time, the tower will not only transform San Francisco’s skyline but it will also serve as a marker for the transit hub, which is expected to have terminals for future high-speed rail coming from San Diego and Los Angeles. “This will have a very important public function. You will be miles away and you will know where the transit center is,” Pelli says. “I think it is very important in a city that we have those markers that orient us. ... It will be fantastic.”