Basin Street Properties is selling $263 million worth of office buildings in Sonoma and Marin counties in what is described as the biggest real estate deal in the North Bay.

The sale to Chicago-based Equity Office Properties Trust represents a move toward diversification for Basin Street, said Matt White, the company's president.

Among the buildings being sold is the Redwood Business Park in Petaluma, where White's father Bill White laid the groundwork for Sonoma County's telecom boom in the 1980's.

The sale includes about 50 percent of the company's holdings in terms of value and 80 percent of its operating buildings, White said.

Basin Street intends to remain in the North Bay and will be reinvesting much of the proceeds of the sale into new ventures, including hospitality, office, mixed use, retail and residential, White said.

Among the cities that will see new Basin Street projects will be Petaluma, Santa Rosa and Windsor, White said.

Neither Petaluma's Theater District or its Napa holdings were part of the Equity Office deal.

-- Jose L. Sanchez Jr.