Trefethen’s Earthquake Recovery Shows Preservation and Structural Work in the Same Building

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Trefethen’s historic wooden winery offers a Napa example of preservation as active engineering work. The building’s recognizable appearance survived a major earthquake through a carefully described repair and retrofit effort. Its story helps explain why historical character and structural intervention are not opposing categories.

A wooden winery with a specific production history

Trefethen’s own account describes the winery commissioned by the Goodman brothers in 1886 and built by Hamden McIntyre at Eshcol Ranch, near the Oak Knoll railroad station. It identifies the building as a three-level gravity-flow winery and traces its later restoration by the Trefethen family.

The production arrangement and construction material make the building more specific than a generic historic facade. A multi-level working structure has a relationship to how fruit and wine moved through it. Its place near transport infrastructure also belongs to the agricultural story, connecting the vineyard and cellar with a wider economy.

The 2014 damage required more than a cosmetic repair

ZFA Structural Engineers’ project account describes severe damage in the August 24, 2014 South Napa earthquake, with upper portions displaced by approximately four feet. The engineers explain their coordination with the owners and historic architect to preserve existing framing while adding connections and reinforcement.

The account describes retained stone foundations, repaired framing and steel components added where needed. These are the project team’s descriptions of completed work, not a current inspection by Diamond Group Estates. They show that preserving a building can involve substantial work within and between the original components.

The winery’s restoration narrative adds the painstaking treatment of exterior redwood siding: pieces were removed, cleaned and cataloged. That is a different process from replacing the whole surface with something that merely looks old. The physical material itself formed part of the preservation objective.

Appearance and performance tell different parts of the story

A repaired historic window, a reinforced connection and an added structural frame can serve different purposes in the same project. Some preserve visible character. Others improve how loads pass through the building. A visitor looking only at the exterior may not see the work most important to the latter function.

This is useful context for anyone interested in historic Wine Country property. A familiar appearance does not establish that a structure is untouched. A carefully modified building can retain significant historical fabric. Conversely, a visually convincing restoration does not by itself establish a particular level of structural performance.

The relevant question is what work occurred, why it occurred and what the resulting system was intended to accomplish. A project narrative from the professionals who performed it is more informative than inferring everything from age, style or a general description such as “restored.”

Continuing use gives preservation an operating context

Trefethen’s example joins cultural history with a working agricultural property. Preserving the winery did not mean freezing the estate at its nineteenth-century operating condition. It involved enabling a historic building to continue within a later business and its requirements.

That relationship helps explain local character in the Oak Knoll area: the region’s agricultural heritage is expressed through buildings that have been used, repaired and adapted. Understanding those layers gives the place more depth than treating every historic feature as a decorative amenity.

Our guide to winery facilities provides the wider property context. Explore real estate and home for sale in Napa, or contact Diamond Group Estates about a property’s physical and historical setting.

Sources reviewed October 28, 2026. Descriptions are attributed to the winery and project engineer. No current structural certification, inspection, affiliation or sale availability is implied.