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The Wells Fargo Bank Headquarters building is located in the heart of the financial district in downtown San Francisco. The maintenance staff had coped with leaks in the buildings’ penthouse roofs, for a number of years. A source of some leaks was a roof membrane under a Japanese garden designed by the notable California landscape architectural firm RHAA, of Mill Valley and San Francisco, Calif. The garden was situated over the Bank’s executive offices and was viewable from the corporate boardroom and dining facilities. It was determined that a roof replacement was necessary, with the project to begin in the fall of 2000. The retiring CEO of the bank requested that the Japanese garden be preserved in its entirety and that the project be completed upon his retirement in the spring of 2001.

Material removal and transport which was done through public corridors that had to be reopened to the public after each work shift.An effective collaboration of design, construction and restoration of the roof and garden, with minimal disturbance to the Bank’s executive officers closest to the work, was the Bank’s number one goal. Another prime objective was to fully preserve the Japanese garden design. The Bank’s project representative made clear that a successful project would be one that would go virtually unnoticed by the building inhabitants. To design and implement a solution to achieve these goals within the necessary time frame would require that design consultants, contractors and subcontractors work together with utmost professionalism and discretion.

Coordinating the work required a delicate balancing act on the part of Western Roofing Service, a Tecta America Company, as the General Contractor and Ron McGinnis, AIA, of McGinnis Chen Associates, LLP, rehabilitation architects, and Ron Wellander, the landscape architect. It was decided that to best accommodate tenants, the majority of the work would take place at night during off hours. Material removal and transport was done through public corridors that had to be reopened to the public after each work shift. The original coal tar membrane was replaced by a thermoplastic, loose-laid membrane system installed on one roof, and a torchapplied, modified bitumen system installed on the other roof. Attaining proper roof slope was a concern; in some locations the original design provided minimal slope and little height, making slope work difficult. Lightweight insulation was pumped up to the 13th floor to provide a roof slope in areas with minimal height. Under the garden, two additional drains were added above the executive offices during evening hours. The garden soil was placed on drainage board above the thermoplastic membrane. All plaza decking was replaced with removable pavers set level on adjustable pedestals.

The original design lives on for future generations to enjoy with a rehabilitation that preserves and enhances the original concept.In order for some of the roof replacement to be done, the Japanese garden had to be removed, disassembled, then put back; stone for stone, block for block, and plant for plant. Once again, precise coordination on the part of Western Roofing was essential. The Japanese roof garden was both restored and rehabilitated. To replace the original membrane below the garden, the entire garden was surveyed and documented within a grid system. The landscape – trees, plants, sculpture and stones – was numbered, tagged, moved and stored for reinstallation, then later put back in the original positions. Garden improvements included pruning, replacing and adding new plants. The paving within the garden area, formally consisting of large aggregate concrete was enhanced with the addition of granite pavers. Dry rot was detected in an original Port Orford cedar platform and was carefully rebuilt with an effort to replicate the original. A new irrigation system was also installed.

As a result of well-coordinated teamwork by Western Roofing and its subcontractors, the entire operation was successfully completed in a timely manner. With few exceptions, the Bank had little disruption of its executive operations. The maintenance staff benefited from a leak-free roof system, with the flexibility to reach and perform new repairs should the need arise. And the original design lives on for future generations to enjoy with a rehabilitation that preserves and enhances the original concept.

Tecta America Corp. headquartered in Skokie, Ill. is one of the largest commercial roofing companies in the U.S. and provides roofing services nationwide through its fourteen companies and 28 locations and over 1,800 employees. Services provided include roof installation, roof replacement, new construction, repair, restoration, and maintenance and full service national roofing management.

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