Presidio Main Post — San Francisco, CA
Lightweight Touch Bolsters Barracks
- 120,000 SF
- BAR Architects
Architectural Resources Group
- Plant Construction
- Blake Marvin
- Sustainable Benchmark
- LEED Gold
- CA Preservation Foundation Preservation
SEAOC Excellence Historic Preservation
Engineering News Record Preservation
The Presidio Trust wanted to preserve the historic Montgomery Street barracks at the Presidio buildings and make them commercially viable, but faced limited public funding and uncertainty about the buildings’ structural integrity. The Trust hired Holmes Structures to address these initially conflicting objectives. We began by asking the right questions to help the Trust rank its priorities for the project: the Trust decided its greatest responsibility was to steward the buildings and provide historic preservation.
The first phases of the project converted Buildings 101 and 103 into commercial office spaces. The Trust’s goal was to preserve as much of the buildings’ original plaster and woodwork as possible while also maximizing leasable floor space. We developed a philosophical approach to use the buildings’ existing masonry and timber to their greatest potential. We invested time in testing and understanding the shear strength of the mortar and used performance-based engineering analysis to determine how the buildings would perform during a seismic event. Our investigation gave the Trust a new understanding of the buildings it had been entrusted with and options for preserving them.
The solution strengthened the existing unreinforced brick masonry using glass and carbon Fiber Reinforced Polymers (FRP). With this innovative technique, lightweight, high-strength fibers are bonded together in thin polymer sheets. The long sheets are then strategically applied over the structure to improve deficiencies. The FRP solution required minimal removal of the buildings’ plaster and woodwork. In addition to the preservation benefits, minimizing demolition and rebuilding reduced the overall project cost by 3 percent and saved an estimated 25 percent of embodied energy relative to alternative construction materials.
By taking the time to ask great questions, listen to the Presidio Trust’s priorities and fully explore the possibilities, Holmes Structures designed a solution that preserved one of the nation’s most significant examples of historic military architecture. At the end of the project, the Presidio Trust decided to use Building 103 for its own office space, so the Trust could share the story behind the buildings’ preservation with visitors.
Our relationship built with the Presidio Trust continues today. Holmes Structures was selected as part of the team converting Building 105 into a boutique hotel. The result of this partnership improves these buildings so that they will continue to meet the Presidio Trust’s mission to create an enduring resource for generations to come.
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