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Buena Vista Winery Cellar Building Structural Strengthening & Rehabilitation

Architect / Firm: Architectural Resources Group

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Architect/Firm

Architectural Resources Group

Pier 9, The Embarcadero, Suite 107
San Francisco California 94111

Contact Person

Naomi O. Miroglio, FAIA
naomi@argsf.com
(415) 421-1680

Architectural Firm

Naomi O. Miroglio, FAIA

Builder

Cello & Maudru Construction Company, Bill Schaeffer
bill@cello-maudru.com, (707) 257-0454

Project Location: 18000 Old Winery Road, Sonoma, CA 95476
Owner: Boisset Family Estates, Jean-Charles Boisset, marketing@boisset.com, (800) 878-1123
Completion Date: 05/17/2015

The Buena Vista Winery is a historic winery complex established in 1857. The oldest commercial winery in California, Buena Vista was founded by the first permanent U.S. settler from Hungary, the charismatic visionary Agoston Haraszthy, and quickly grew into the most prosperous wine making operation in the Sonoma Valley. The historic structures—the Press House constructed in 1862-63 and the Cellar Building constructed in 1864—represent the first gravity feed stone winery buildings in northern California. The winery was placed on the National Register of Historic Places in 1986.

The Cellar Building Seismic Strengthening and Rehabilitation project was a multi-phase rehabilitation project to renew the historic buildings and site, return them to their original wine-making purpose, and create a vibrant hospitality venue that highlights the significant history of the property for a new generation of visitors. Phase 2, completed in May 2015, included the creation of offices on the second floor and development of an historic winemaking tool museum on the third floor, along with installation of an elevator for ADA access throughout the building.

The Cellar Building was in a serious state of disrepair when purchased in 2011, and had been closed to the public since 1990 due to structural instability. The Cellar Building is a three-story masonry building and, as is typical for gravity feed wineries of the period, it is built into the hillside. It retains three original caves carved into the native rock, where the pick marks of the original Chinese laborers are still evident in the hand-hewn stone walls. On the exterior, ivy, which had been planted to conceal a concrete infill wall constructed after a collapse in the 1940s, covered the walls and contributed to degradation of the mortar. Significant structural cracks and severe mortar and stone deterioration were evident throughout the masonry walls.

The project posed significant technical challenges, notably the owner’s stipulation of an “invisible” structural system (a 1981 upgrade of the Press House left the exterior littered with metal plates). The project team employed innovative techniques to reduce the visual impacts of the structural upgrade while maximizing the retention of the original character-defining features, including the stone walls, both hand-hewn and roughly-coursed masonry, the heavy timber framing system, the stone caves and the wide open interior spaces.

Center Core Strengthening

The Cellar Building was constructed of very soft stone, and the values of the walls were such that drastic measures were necessary to ensure stability and safety for the proposed use. Center Core Drilling was chosen because it strengthened the exterior masonry walls with no visible evidence. It had the added advantage of grout migration, where the polyester grout extended into the voids throughout the internal structure of the wall. A single rod of reinforcing steel was placed in each core, which was then filled with grout. The grouted cores created a series of reinforced vertical columns that strengthen the stone wall.

The center core drilling process involved meticulously calibrated drilling equipment; each core responded to the angle of the stone wall in the specific location, since the walls were no longer perfectly straight. In addition, an unusual and innovative technique was employed to anchor the floors to the reinforced stone walls while avoiding any external metal plates on the historic building: the reinforcing rod in each core threads itself through an eyebolt at each floor level. This eyebolt was then connected directly to a steel ledger at the floor. When completed, this connection became essentially invisible.

Masonry Restoration

Significant masonry work was required for both structural and cosmetic reasons. Extensive deterioration and structural cracking was evident throughout the walls. Past, poor-quality masonry re-pointing campaigns had left the building in such a state that it took some lobbying to have the ivy removed at all. Masonry restoration consisted of removing all of the existing mortar, re-pointing the joints, replacing cracked and deteriorated stone with locally quarried stone to match the existing, and repairing wall cracks with injection grout.

The mortar for the re-pointing was carefully created to be compatible with the soft characteristic of the original stone and be visually consistent with the original historic mortar, while achieving the minimum strength values required by the structural engineer. After a number of test mixes, the selected mortar mix contained Natural Hydraulic Lime, a natural material that initially sets with water and achieves additional strength through the absorption of CO2. It has been used for centuries in Europe, and is also the primary ingredient of the pozzolanic cements used during the Roman Empire.

Heavy Timber Framing

The original heavy timber framing system existed throughout the building, including distinctive post and beam elements. Although the condition of the framing was fair, with limited dry rot, the challenge was to meet the load requirements of the structural upgrade and the lateral force requirements without visible new elements to tie the members together. First, it was discovered that reverting to earlier, and in this case more accurate, building codes written for old-growth wood was appropriate for the historic materials. Deteriorated post and beam elements were replaced with new wood elements to match existing, and dutchman repairs were carried out at deteriorated column bases. All new wood elements were treated with an iron oxide solution to pre-age the wood to match the color of the historic framing. Concealed bolts were used to tie the post and beam elements together, and recessed bolt openings were covered with wood plugs.

Caves

Prior to the closure of the Cellar Building Caves, generations of visitors had enjoyed the unique view of history afforded by the stone spaces. The rehabilitation project involved a unique strengthening approach for the historic caves to ensure that the native stone is visible for future generations, utilizing a recessed rock anchor system. Cement grouted rock dowels were installed in the walls and ceiling of the caves, and the holes patched with mortar stained to match the varied color of the natural rock surfaces. Stainless steel micro anchors were installed for minor cracks and fractures.

The project restored a significant site in California and viticultural history, opening it to visitors and vintners alike. A new vintage, the first in decades, is currently aging in oak barrels lining the walls of the restored space.

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