Oakland, Alameda County,
A full seismic upgrade including base-isolation was the primary goal of this project. Repairs to the interior marble surfaces of this local landmark incuded fabrication, repairs, and resurfacing.
The overall plan called for the installation of base isolators under the actual building frame, to isolate the structure from the dramatic shear forces that occasionally wreak havoc upon California. In the case of Oakland City Hall, an entirely new iron frame was installed inside the original building shell, and tied to the new base isolators installed in the sub- basement.
Here, the 'skirt' supporting the main body of the building has been partially installed on top of the new base isolators in the sub-basement.
After all structural work is completed, the new supporting 'skirt' is clad in matching grey granite.
In all cases where salvaged marble was installed to hide previous structural work, we were obliged to also resurface the newly installed marble so that it would match the appearance of the other original material not previously removed.
Each area of newly installed salvaged marble was prepared so as to assist in the final resurfacing process that would make old and newly installed material match in all respects.
All of the marble flooring in the entire building was resurfaced using diamond abrasives in conjunction with water to lubricate the honing process and carry the marble slurry away to be picked up by vacuum.
As this image shows, the effect of a single pass of honing could be dramatic. The honing process removed years of use, scratches, and old wax, yielding a 'new look' surface. During the entire honing process, only about .003 of an inch of marble was actually removed.
The diamond technology we employed was originally developed for the glass industry, so it seemed especially appropriate to use these abrasives on this glass insert in the marble floor.
New ramps were added at two locations to satisfy requirements for handicapped-accessible areas. Salvaged marble was used for this area as well.
The salvaged marble slated for installation had to be carefully resurfaced using pneumatic bush hammers to yield a roughened surface for traction. We went through three different bush hammer types before the right surface was found.
The finished handicapped ramp was trimmed in black Marquina marble to highlight the area visually and echo the Belgian black marble trim found throughout the original installation.
Chemical cleaning was used in many areas where a mechanical resurfacing technique would have been too labor intensive. Simple alkaline-based compounds proved very effective for this activity
Of course, our 'natural' honed look (with attendant low-maintenance profile) was wiped out when the new building manager ordered the floors to be coated with wax, since they were not 'shiny' enough. All good intentions, etc........