Oakland’s Luminous New Cathedral
MATERIALS:
Although the cathedral’s exterior has a glassy appearance, Douglas fir, the wood with a regional pedigree, is the interior’s dominant material. The structural members of the building’s exterior wall are premium select grade Douglas fir with a finish of clear penetrating sealer to maintain their natural quality. The horizontal slats set between the curved vertical wood ribs of the louvered wall sections have a surface layer of slotted and perforated wood acoustic panels to absorb sound inside the building. The curtain wall’s laminated glass has a fritted inner layer of white ceramic paint applied in a variable linear pattern. The translucent glass filters daylight and enhances the glow from interior light at night. The fritted layer also reduces heat gain on the interior. Rotation of the individual glass panels to make the pattern vertical or horizontal varied the wall’s visual effect with minimal means and expense.
Photograph by Sally B. Woodbridge
The concrete used in the Reliquary Wall contains a high percentage of fly ash, a recycled industrial product that may be substituted for a certain percentage of Portland cement. The fly ash both reduces the shrinkage that increases cracking and improves the concrete’s workability and density.
SEISMIC SYSTEM
The diocese’s desire for a cathedral that would last 300 years meant that, given the Bay Area’s active seismic zone, the building would have to be designed to withstand a major earthquake. To meet this challenge a structural foundation system using thirty-six friction-pendulum base isolators was constructed to significantly reduce the seismic forces transmitted from the ground to the building. This system also permits a much lighter structure than would otherwise be required in a conventional building with a fixed base. Since base isolation allows the building to move independently of the ground during an earthquake, the area where the movement might occur is constructed as a moat encircling the base of the building that provides approximately three feet of space for movement in any direction. The pin connections that attach the exterior wall’s wooden structure to the Reliquary Wall were designed to allow rotation relative to this concrete base. The curtain wall’s glass panels also have the ability to slide within the vertical steel support structure when subjected to a significant earthquake.
PROJECT SCOPE
Besides the cathedral, the site will have a landscaped plaza open to the public, underground parking for 200 cars, a parish hall and offices, conference facilities, chancery offices and a rectory, the bishop’s residence, a cafe, and a bookstore. The site plan connects the cathedral to Lake Merritt and the city with public plazas, gardens, and courtyards. In addition to its significant effect on the spiritual life of the Bay Area the cathedral will make a unique contribution to the architecture of the region and beyond through its form, structure, and materials.
