The first office tower completed in San Francisco since the Great Recession, the 28-story, 350,000-sq-ft, steel-framed building sits in the city’s evolving South of Market (SoMa) district.

The economic downturn stopped the $93.4-million project after shoring and basement excavation had been completed. General contractor Swinerton Builders regularly monitored the site and kept the original building permits active to be ready when the project came back to life.

In addition, the contractor helped the previous owner find a new buyer and interviewed 10 developers until the property was acquired in late 2012. Swinerton restarted and engaged all subcontractors to confirm a guaranteed maximum price, revise the schedule and restart construction.

With the adjacent Transbay Transit Center already underway when construction resumed, the team had to contend with constrained laydown and staging areas. “This required extensive coordination of construction activities and concise delivery scheduling for all building components,” says Terry McKellips, Swinerton’s vice president and division manager.

The company also had to coordinate with project subs to explain “vertical” sequencing—a strategy that calls for working on more than one floor at a time. “Since the majority of subcontractors maintain a ‘horizontal,’ or floor-by-floor intuition, we educated them on this more efficient vertical sequencing concept. This kept the project schedule on track for an on-time completion date,” McKellips says.

A temporary steel bridge over the Mission Street sidewalk electrical vaults became an unusual staging area.

An energy-efficient unitized curtain wall system has a radiant low-e coating and air gap. To reduce shadows on surrounding properties, the tower tapers at its corners. Other sustainable features—which helped the project become the first LEED Platinum Core & Shell-certified office building in the city—include a stormwater retention system, advanced mechanical systems, improved indoor air quality with air-economizer ventilation systems and extensive daylighting.

535 Mission Street

San Francisco

Key Players
Boston Properties Inc.
Lead Design Firm HOK
Contractor Swinerton Builders