Carnegie Library gets a well-hidden retrofit
Round the turn of the 19th century, hundreds of communities throughout America and other parts of the world were very fortunate to have been granted community library construction donations from businessman and philanthropist Andrew Carnegie. However, the building methods of those times used unreinforced brick and stone for most of the libraries, which do not perform well in California’s earthquake-prone regions.
The Historic St. Helena Carnegie Library was completed in 1908 with a construction budget of $8,362 donated by Mr. Carnegie. It functioned as a library until 1979 when the city library’s needs exceeded the capacity of the building. In the ensuing years, the building was used as the City Council Chambers, public meeting rooms, and offices for the St. Helena Parks and Recreation Department before being closed due to the work required by St. Helena’s seismic retrofit ordinance regarding public safety.
The two-story building, with a partial basement, is relatively small, at around 2,900 square feet of floor space. However, with up to 22-inch-thick rubble stone walls, what the structure lacks in space it makes up for in mass. The heavy walls tend to generate large inertial forces during earthquake ground motion, thus requiring substantial anchorage connections at roof and floor levels to keep the walls from collapsing in a major shaker. Being a historical building, significant emphasis was put on preserving the exterior facade and interior finishes during the structural retrofit design phase. Large, steel washers on the exterior of the walls are exposed or made to be “decorative” in a typical retrofit; however, ZFA Structural Engineers was able to design a connection that could be hidden within the stucco walls and patched over to completely conceal unsightly structural material from view.
On the interior of the building, conventional design approaches would have caused much of the historical aspects to be modified or completely lost. Rather than using typical concrete bond beams at the wall perimeter, ZFA located steel members behind beams, walls, and finishes and reinstalled preserved mouldings so that the structural work is completely hidden within original building cavities. Careful detailing allowed irreplaceable wood flooring and hand-crafted mouldings to remain largely in tact.
As part of the rehabilitation, ADA compliance was also necessary and a challenge for this historical structure. Providing an elevator that would serve the basement and two floors, including a split-level main floor, was not an easy task. Using a unique elevator system with a very shallow pit and minimal height requirement above the cab, the architect, Valley Architects of St. Helena, minimized the impact it had on the architecture as well as the structure.
With the addition of a new faux balcony, matching the appearance of the original one that had been removed at some point, the new, rehabilitated, and preserved, Carnegie Library will continue to serve the community of St. Helena for another century.