Oslo, Norway-based architects Snøhetta have been appointed to design a new US$250m (£164m) expansion to the San Francisco Museum of Modern Art (SFMOMA).

The project, first announced in April last year, will incorporate additional gallery space and interior improvements in the museum's Third Street building, together with an extension on Howard Street - to the south - that will connect to the back of the existing museum along the southern facade.

SFMOMA owns the site at 670 Howard Street and, following an agreement with the City of San Francisco, the development will also include a neighbouring site presently occupied by a fire station. This will be replaced by the museum with a new, US$10m (£6.5m) facility on Folsom Street nearby, with the museum's expansion proceeding as the new fire station is built.

The museum's current building occupies 225,000sq ft (21,000sq m) with nearly 65,000sq ft (6,039sq m) of galleries, including the 14,400sq ft (1,338sq m) Rooftop Garden. The expansion will provide approximately100,000sq ft (9,290sq m) of additional gallery and public space.

The expansion will also include approximately 60,000sq ft (5,574sq m) of support space, including larger and more advanced conservation facilities and an expanded library. SFMOMA plans to relocate administrative support space into the new facility, providing new gallery and public space in its original building, while consolidating all staff offices to one on-site location.

The project may also include a new entry on Minna Street - which runs along the museum's northern facade - to improve access for school groups and for visitors to the museum's Phyllis Wattis Theater for public programmes.

The current timeline for the scheme sees initial design concepts being released in Spring 2011, the new fire station opening some time in 2012, construction of the new extension beginning in 2013 and it opening in Spring 2016.

Image: WolfmanSF