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In Full Bloom: The Conservatory of Flowers by Architectural Resources Group and Tennebaum-Manheim Engineers

San Francisco: Extreme historic and environmental preservation methods bring a deteriorated treasure back to life.

by ArchNewsNow
October 7, 2003

When the wealthy businessman James Lick died in 1876, he left behind a mysterious treasure in his San Jose barn: crates containing the pieces of a 12,000-square-foot conservatory, origin unknown. San Francisco businessmen bought it and gave it to the San Francisco Park Commission, which assembled the structure and opened it to the public in Golden Gate Park in 1879. Filled with rare flowers and exotic plants, the Conservatory of Flowers survived an exploding boiler, the 1906 earthquake, and a fire before a 1995 windstorm smashed thousands of its glass panes and broke several wood arches. The conservatory closed, its future uncertain. But eight years and $25 million later, the oldest public greenhouse in California reopened its doors to the public on September 20, 2003.


Storm damage wasn't the only problem. The delicate Victorian structure – made of old-growth redwood, Douglas fir, and sugar pine ­– had deteriorated drastically over the decades, as a result of iron nails degrading the wood, high humidity from an inadequate ventilation system, and a lack of waterproofing.


One of the toughest challenges facing the team from Architectural Resources Group (ARG) and Tennebaum-Manheim Engineers (TME) was figuring out how to replace the wood while meeting the Secretary of the Interior's Standards for the Treatment of Historic Properties. Although some of the wood could be reused, all 100 wood arches had deteriorated too much. Substituting aluminum wouldn't meet the historic standards. Chopping down old-growth redwood wouldn't be environmentally sensitive. Young-growth redwood would take too long to pressure-treat. In the end, the designers chose "buckskin logs," the term for old-growth redwood that has fallen naturally or been left behind by loggers. A special subcontractor tested each wood piece for structural strength. Most pieces were hand-milled on-site to match original profiles.


Complicating matters, the original drawings no longer existed. The project team first disassembled, analyzed, and reconstructed 900 square feet of the west wing as a test run, to see how the building was put together and if it could be rehabilitated and put together again. Because the building and the plants were so delicate, surveying the conservatory required some creative thinking. “On the exterior, our survey team applied temporary wood support pieces in order to scale the curved structure,” says David P. Wessel, AIC, ARG’s lead architectural conservator. “Inside, we hung a boatswain’s chair from the dome, to carefully study the interior.”


In addition, rare plants had to be relocated during construction ­– but a few of the largest historic specimens, including a 100-year-old philodendron, couldn't be moved. The restoration crew surrounded these with temperature-controlled enclosures during construction.


The addition of new elements needed to be invisible, or at least in keeping with the original building. New automated environmental control systems operate the heating, ventilation, and fogging systems, simulating the native environments the plants need to survive. These are now concealed in trenches, walkways, and new routing systems. To address modern ADA access requirements without adding handrails or other visually disruptive elements, the designers sloped floors to connect different levels of the building. The seismic strengthening approach involved a structural scheme combining new foundations and steel reinforcement. “Where possible, we concealed the steel plates within the wood structure, and then added slender exposed trusses and bracing rods to complement the structure’s light and delicate quality,” says TME structural engineer Nancy Tennebaum, P.E.


The rehabilitation campaign was accomplished through a cooperative partnership between the San Francisco Recreation and Park Department and the non-profit agency Friends of the Recreation and Parks. Funds came largely from private donations, bolstered by federal, state, and local government grants and city parks bonds.


“The commitment and tenacity to realize this project was phenomenal, from all the parties involved, especially the volunteers and the donors,” says Bruce D. Judd, FAIA, a principal of ARG. “The Conservatory is a major historic preservation success story. We hope this type of public-private partnership serves as a model for restoration projects throughout the country.”



Client: San Francisco Recreation and Park Department; supported by Friends of Recreation and Parks

Project & Construction Management: San Francisco Department of Public Works

Architect & Engineer: Tennebaum-Manheim Engineers in association with Architectural Resources Group

Exhibit Design: The Portico Group

Mechanical Engineer: Mechanical Design Studio

Electrical Engineer: POLA, Inc.

General Contractor: ISEC Inc. and Troy’s Contracting, a joint venture


Architectural Resources Group, Architects, Planners & Conservators, Inc., is a San Francisco-based architecture and historic preservation firm founded in 1980. The firm had been responsible for the adaptive reuse and seismic strengthening of existing structures, the documentation and restoration of historic properties, and the design of new structures that fit into historic surroundings. Well known projects include the Conservatory of Flowers in San Francisco's Golden Gate Park, the Filoli Estate and Visitor's Center in Woodside, and the Language Center at Stanford University.


Tennebaum-Manheim Engineers is a structural engineering firm located in San Francisco offering extensive experience in historic rehabilitation as well as the design of new structures. TME participated in the design and innovation of new structural design technologies for projects such as the Seismic Retrofit of San Francisco City Hall.


See also:


A New Yet Familiar Neighbor: Goldman School of Public Policy UC Berkeley by Architectural Resources Group


Ruins Reclaimed: Scott and Montgomery Halls at San Francisco Theological Seminary by Architectural Resources Group

(click on pictures to enlarge)

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
The Conservatory of Flowers in full bloom

(Catherine Lyon-Labate (c) Conservatory of Flowers/Friends of Recreation and Parks)
The Conservatory glows at night

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
View from the inside out

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
View from the outside in

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
The painted exterior before restoration began

(Ted Kurihara (c) Conservatory of Flowers/Friends of Recreation and Parks)
Restoration begins

(Ted Kurihara (c) Conservatory of Flowers/Friends of Recreation and Parks)
Interior detail during restoration

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
Restoring the roof

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
A lily pond before

(Kevin J. Frest (c) Conservatory of Flowers/Friends of Recreation and Parks)
A lily pond after

(The Portico Group)

© 2003