(Wine-Searcher) - A dramatic three-year refit of Joseph Phelps Vineyards' iconic St Helena headquarters will put the winery at the forefront of the booming Napa tourism business, according to the company's marketing director.

Phelps, and its flagship wine Insignia, is one of California's most renowned producers. Its founder, Joseph Phelps, who died in April, built his classic redwood "California barn" winery, with its distinctive trellis bridge, in 1973.

Forty years later, the winery has been extensively enlarged and repurposed, with multiple tasting rooms and dining areas carved out of the original barrel cellar, a 1000-bottle display library and a redwood balcony overlooking the vineyards.

The point, as sales and marketing director Mike McEvoy told Wine Searcher, is to capitalize on booming wine tourism in the Napa Valley.

"Napa has become an international leader in wine tourism, and we were falling behind. This puts us back in front."

The most arresting part of the development is the transformation of the fermentation room, which becomes what McEvoy calls the "Great Hall". The barn-like space, which four years ago held stainless steel fermentation tanks under a 40-foot ceiling, has been split into five different rooms.

Each is lined with redwood, with intricate latticework echoing the famous bridge-like structure on the outside of the building.