Construction is well underway for the San Francisco Museum of Modern Art (SFMOMA) expansion by Snøhetta, with local firm EHDD Architecture. Scheduled for completion at the end of October 2015, with an opening exhibition in early 2016, the 235,000-square foot project now wears a largely finished exterior envelope.

A white undulating skin distinguishes the new addition from the masonry stripes of Mario Botta’s 1995 design. Composed of 700 fiberglass reinforced polymer (FRP) rainscreen panels, the new facade incorporates insulation and a fire-resistive concrete finish. The FRP panels, which are significantly lighter than GFRC panels, were designed in conjunction with fabrication team Kreysler and Associates and facade specialists Enclos.

Interior construction is proceeding and one of the highlights of the new design is the amount of space devoted to public access. The entire sequence from the existing Third Street entry lobby through the new 7,750-square foot Art Court admissions area and the 6,700-square foot Howard Street lobby is open to the public, allowing for pedestrians to view artwork without entering the paid areas of the museum. The new Howard Street facade is set back, creating a public alleyway that connects to Natoma Street. When it opens, the new addition will feature wood flooring and black Chinese granite columns to match the existing building.

The Doris and Donald Fisher Collection, a major impetus for the expansion, will be housed primarily on the fourth, fifth, and sixth floors of the new wing. The new construction, however, required some significant changes to the original Botta-designed building, including the removal of the iconic cubic central staircase, which was replaced by an open wood lined stair that leads to the second floor Art Court for ticketing.

By removing the old staircase, the renovation allows significantly more sunlight to pour from the existing circular oculus above into the main atrium space, noted Snøhetta founding partner Craig Dykers. The new stairs connect to the public lobby as well, which can also be reached by the grand staircase off of the Howard Street entrance. Already in place, Richard Serra’s curvilinear sculpture Sequence (2006), dominates that entry. The artwork was moved from Stanford University and installed in early February. Due to its size, the sculpture had to be placed before installing the Howard Street lobby’s double-height glass facade.

Construction challenges included the downtown site itself, which is tightly constrained between the two alleyways of Minna and Natoma Streets. The narrow site made the stabilization of construction cranes difficult. Due to the lack of a staging area, general contractor Webcor Builders had to strictly coordinate the movement of construction materials and vehicles during the entire construction sequence.

The ten-story addition aligns with the existing five-story structure; the design intent of the expansion was to double the size of the existing galleries by creating a seamless transition between the old and new gallery spaces. The rear facade of the Botta building was removed and the existing veneer brick precast panels carefully peeled off. Working with structural engineer Magnusson Klemencic Associates, existing structural columns were demolished to create 60-by-150 foot column-free gallery spaces. To support these new large spans, structural hangars were installed to transfer the floor load to larger beams above, which, in turn, are supported by columns that carry the load down to the foundation.

The new structure affords views of the city via a selection of outdoor spaces. In addition to the original veranda-like spaces on the fourth floor and the rooftop sculpture garden designed by Jensen Architects with CMG Landscape Architecture in 2009, Habitat Horticulture and Hyphae Design Lab will transform the wall of the Botta building that faces the third floor terrace into a vertical garden. The expansion is targeted for LEED Gold certification, a goal aided by recycling gray water for irrigating the vertical garden. The seventh floor terrace will frame the city, offering expansive views of the skyline and the San Francisco bay.