Removal and repairs to the limestone elements of this early building on the UCLA campus involved disassembly and later reassembly of the limestone units.
The salvaged limestone was unfortunately stored without overhead protection and with the concrete core intact. After several seasons of rain, the water-soluble calcium-based elements of the core were flushed to the surface of the limestone and deposited as efflorescence.
We came on the job to inventory the "salvaged" limestone spires and discovered a hodgepodge of masonry in storage with little or no documentation to support re-assembly efforts.
Careful disassembly then took place. Each large section of limestone spire was cut around each grout line until the section could be further deconstructed to the basic masonry units.
Each limestone spire unit was further cleaned by removing old setting and pointing mortar.
Final preparation of the masonry included removal from the original concrete core.
Each limestone unit was pre-assembled after surface preparation to verify placement in the final layout and elevations.
Specialty cleaning included a custom pulp-based poultice for all 600 pieces of limestone to remove the alkaline salts leached from the concrete cores. Each piece was further cleaned with a pressure rinse system that incorporated a de-ionization filter in the water line to help reduce the chance of further efflorescence.
Meanwhile back at the job site, the original base of each spire was prepared by first removing the old concrete support pads,and exposing the original corner base supports.
After this upper level of concrete was removed to expose the original hollow support cylinders, we installed new steel dowels to tie into the new structural iron reinforcing the limestone.
The first layer of limestone at each corner spire involved not only setting the limestone units, but installing concrete in the base hollow, to tie in the new limestone tower spires.
As each level of limestone components was added, the concrete and steel inner reinforcement was tied in to the exterior masonry veneer.
Any reinforcing bar that penetrated limestone was either epoxy-coated or made from stainless steel.
Each cavity around the reinforcing bar was filled with epoxy adhesive to yield an extremely strong installation.
During the installation of those layers that were anchored with internal steel rods each piece was carefully lowered onto the setting bed level below.
As each layer was installed, the setting bed mortar was cut back from the decorative face of the stone to leave room for the specially formulated pointing mortar, colored to match the original in texture and color.
Over 20 courses of limestone were installed for each of four towers in successive installations.
Cleaning of the entire building was achieved after extensive testing to determine the optimum combination of cleaning effectiveness and gentleness of methods. Because the limestone components of the building were not made of the most durable building stone, special care was taken to use a moderate pressure water rinse. No chemicals were used since the water-only rinse method was shown to be effective at removing all but the most stubborn deep-seated stains.
This simple cleaning method had the added advantage of dramatically lowering cleaning costs because there were no hazardous waste disposal issues.
The same de-ionized water system with moderate pressure (<1,500 psi) was used to clean all brick and limestone surfaces on the building,
Note that in these before and after shots of the cleaning the runoff patterns from the rain have deposited stains in the limestone window headers and other horizontal elements.
The cleaning program was not designed to remove 100% of all stains, since that would have entailed possibly removing the outer layer of stone to get to the deep-seated stains. The building was lightened in value by as much as 50% in some areas but it was not 'over-cleaned'.
The freestanding floral elements were carefully removed from the building and the original steel anchoring rod removed from the limestone by coring around the ferrous material.
New stainless steel pipe was used to re-assemble the decorative limestone pieces and to serve as the new anchor to the building parapet.
Again, epoxy adhesive was used to provide the strong attachment needed in case of future seismic events.
Several of the bases had been significantly damaged by the expansive rusting action of the old steel anchors. Specialty patching mortar was used in these locations to rebuild the damaged portions.
Here the final cap piece has been installed and now all that remains is the installation of the pointing mortar in the joints between masonry units.
Kerckhoff Hall has been prepared, inside and out, topside and below, to serve the community of UCLA far into the foreseeable future.