Peña Adobe Structural/Seismic Strengthening and Rehabilitation - Vacaville, CA 
 

Constructed in 1842, the Peña Adobe is the oldest standing structure in Solano County and a designated California Historical Landmark (#534). Built by mission-trained Indigenous craftsmen using locally sourced materials, the adobe was formed from handmade 23" x 10" x 3" mud bricks, sun-dried on site and set with hand-hewn redwood timbers cut from the nearby Napa hills. Its two-foot-thick walls and simple dirt floors reflect the vernacular architecture of early California and the practical craftsmanship of its era.

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Today, the Peña Adobe stands as the centerpiece of Peña Adobe Park—a one-acre historic site located just off Interstate 80 in Vacaville. Once the home of the Peña family, the structure now serves as an enduring link to the early Rancho period and the beginnings of settlement in the region.

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Treeline Construction was contracted by the City of Vacaville to perform a comprehensive structural and seismic strengthening of this fragile historic landmark. Our work included the installation of a reinforced concrete bond beam atop the adobe walls, replacement of deteriorated roof structures, and reconstruction of missing or damaged adobe blocks—all fabricated on site using adobe material excavated from the property to ensure historical authenticity.

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To stabilize the structure against lateral and seismic forces, Treeline pinned the building’s corners together using six-foot fiberglass threaded rods set in epoxy, repaired structural cracks, and restored the original adobe walkways. All work was completed with sensitivity to the historic fabric and under the guidance of architect Gil Sanchez, whose collaboration and expertise helped ensure the project’s success.

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The restored Peña Adobe continues to serve as a tangible connection to California’s early history—preserving the legacy of the Peña family and the skilled craftsmanship that defined the state’s earliest architecture.