written by:
October 24, 2012

This blog series profiles a new prefab development in San Francisco's SOMA neighborhood—a LEED Platinum-targeted building containing 23 "micro-studios." Built in a California factory in a month and assembled on-site in just four days, these 300-square-foot units are paving the path to a new approach to prefab—and to small-space city living. PART THREE: Factory construction and on-site assembly.


Harriet Street represents the culmination of ZETA Communities’s original vision to build ultra-green multifamily and urban prefab buildings. Prefab multifamily projects have been built all over the world as global developers have realized the benefits; witness this time-lapse video (with almost five million views) of a 30-story modular building erected in just 15 days in China.

In ZETA's factory, an acoustic model was tested by Salter Engineering. It received one of the highest acoustic ratings—a very important consideration for small spaces so they don’t feel crowded at a high density. Later, developer Patrick Kennedy conducted some amateur testing and cranked up music on a bluetooth speaker—and couldn’t hear it in the next door unit.
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The first unit was built as a model to test quality, design, structural, and other key aspects of the building.
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Here's the ceiling being craned into place.
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It took about a month to construct all 23 micro-units, each around 300 square feet. Each completed unit contained all interior finishes, from plumbing, electrical, and drywall to cabinets, flooring, and light fixtures.
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When the modules were completed in the factory, they were shipped to the site in stages. At the destination, crews faced challenges typical of a dense urban infill site, with narrow streets and traffic.
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Each day four 65-foot modules were craned into place. Three modules contained a total of six units units; the fourth module contained a four-story stair atrium/elevator. This stacked up to one floor per day.
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Crews set the final module in place. With only 1/8" tolerances between each unit, it was quite a feat. Over the following weeks, the corridor, roof, and exterior cladding will be completed. Stay tuned to see the finished product!
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In ZETA's factory, an acoustic model was tested by Salter Engineering. It received one of the highest acoustic ratings—a very important consideration for small spaces so they don’t feel crowded at a high density. Later, developer Patrick Kennedy conducted some amateur testing and cranked up music on a bluetooth speaker—and couldn’t hear it in the next door unit.

Naomi Porat, ZETA's cofounder and former president, sees prefab as "ideal for zero lot line urban infill conditions… off-site construction is inherently efficient by generating 80 percent less construction waste and reducing  construction time by more than 50 percent." Another bonus, in the case of the Harriet Street project, was that off-site construction minimized disruption to the surrounding dense neighborhood during the accelerated construction process, "which is key to securing permits without neighborhood permits," says Porat.

Asked to elaborate on the trends driving their experiment with micro-unit living, Porat says:

"There is a significant mind-shift in urban dwellers, who are trading physical living space for connection and shared social spaces within the larger city environment. Efficiently designed smaller dwelling units, sites in the urban core, proximity to public transit, and networked residential development are the now the hottest amenities in the market. These trends are driven by pure economics and technological advancements. Smaller, energy-efficient residential units allow urban dwellers to spend less on housing. Mobile devices are dramatically reducing the need for physical space dedicated to technology. And major shifts in office environments, especially in the tech sector, provide employees with the kitchen, living room, and social space to spend longer time in the workplace. These factors will fundamentally change design for residential and commercial development in the future."

Here's a look at how the project came together in Zeta's factory in Sacramento and on site. For more, click through the slideshow.

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