Perspectives December 10, 2020

What it took to preserve San Francisco’s historic Building 12

By Ariane Fehrenkamp, Senior Project Manager, and Meaghan Dufford, Senior Project Architect

The historic Building 12 in the process of being lifted.

Credit: Brookfield Properties/Plant Co.

Long before the Pier 70 project began, developer Brookfield Properties and the Port of San Francisco determined that the new neighborhood to be built here must address a 100-year projected sea level rise and that Building 12, which once housed the fabrication and cutting of steel sheets for the hulls of the ships built at Pier 70, is a significant historic resource. For the Building 12 design team, these two requirements set forth a design journey that could be deemed heroic, is most certainly innovative and, in some ways, backwards.

To address sea level rise along waterfront sites, there are typically two options: bring up the site grades or construct sea walls along the shoreline. At Pier 70, Brookfield Properties chose to raise the site roughly 10-feet. For new construction, one would simply set the new first floor level at the new grade, however for an existing building, such as Building 12, this decision presented a conundrum. Once the new site grades were complete, the existing first floor would reside some 10-feet below ground. This is clearly not the way one treats a valued historic resource. In a move ill-fitting for the faint-hearted, it was decided that Building 12 would be lifted along with the site.

From the start of project designs, the goal was to let history shine through and to prevent the act of lifting the structure from leaving excessive scars on the building. The challenge was to design in anticipation of the lift—designing for this moment, as well as for the future use of Building 12.

Unique Challenges

Lifting a building presents its own challenges. The roof is typically installed as the final piece of the building’s shell. Topping off, as the industry calls it, is often grounds for celebration. However, Building 12’s iconic Aiken roof—defined by its irregular shape and rows of high windows—in addition to the footings had to be the first structural components to be completed. The reason for this is simple. The existing Building 12 is a two-story shed structure, with shear strength provided by the ground floor, the second-level floor, and the roof. The original wood roof was in bad shape, having suffered years of water damage. The existing ground-level floor was slab on grade which would not be lifted. So, to prepare for lifting Building 12, temporary bracing beams were installed at the first-floor level and at the roof, the monitor window glass was removed and new roof sheathing installed to make the building rigid enough to prevent it from racking during the lift.

Wood cribbing stacks

Credit: Brookfield Properties/Plant Co.

Lift shoring towers

Credit: Brookfield Properties/Plant Co.

Lift shoring equipment

Credit: Brookfield Properties/Plant Co.

Preserving Historic Character

The age-earned patina of Building 12’s corrugated siding provides much of Building 12’s character. The team realized early on that removing it and replacing it once the walls were properly constructed would be rather like unraveling a sweater—impossible to puzzle back together. In order for the siding to remain in place during construction; the walls, too, were designed to be built in reverse order.

Another of Building 12’s defining historic features are the huge built-up columns that run around the perimeter and in two rows down the center, dividing the interior space into three bays. Each of these massive 4.5’ x 2’ columns grounded at a gusseted base and a thick baseplate that was bolted to the original ground-level slab. This condition was one that we wanted to preserve and to keep visible in the new building.

Our obsessive detailing had to be both precise and incorporate wiggle room for unknown elements. Over the last 60 years, differential settling had resulted in variations in the baseplate heights. A survey of the exact elevation of each column base allowed us to dial in the specific extent of the lift, determine the new elevation of the first floor, and keep the base of the built-up columns visible—rivets, bolts and all.

The completed Building 12 will be home to makers and artisans.

Credit: Brookfield Properties

Looking Forward

This week, the original structure, with all its imperfections and irregularities, will be set down on new precisely constructed columns and concrete retaining walls. From this point, a more logical construction sequencing will follow. In a couple years, when future makers and shoppers walk past the patinated building’s new curtain wall and pour inside through the huge red entry portals—an homage to the hue of historic paint—traces of the lift will be discernible just below eye level in the clean line of the lift band. This is just one of the many modern interventions that will coexist with the industrial craftsmanship of Building 12’s past.

What it took to preserve San Francisco’s historic Building 12

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