A group of local investors have teamed with an international backer to pull off the largest acquisition of North Bay commercial real estate in recent years, paying $65 million for 14 office buildings in Petaluma and Rohnert Park.

In the deal, PB&J Acquisitions, a Bay Area corporation, and Investcorp, which trades on the Bahraini stock market, combined to buy nearly 841,000 square feet of office space along the Highway 101 corridor.

The properties, acquired from San Francisco-based RNM Properties, are home to a variety of prominent tenants, including Amy's Kitchen, CamelBak, Clover Stornetta Farms and Athleta, a division of Gap.

But they also include plenty of available space. The portfolio was about 74 percent occupied at time of the sale, said Bill Sumski, an attorney and partner in PB&J who splits his time between Petaluma and San Francisco.

"There is some leasing to do obviously," he said. "We have some big holes."

The new owners will put special emphasis on leasing out 1800 S. McDowell Blvd., a 73,000-square-foot building built in 2007 in Petaluma and never occupied, said Sumski, who described the property as the jewel in the portfolio.

"We certainly will be looking for marquee tenants to land there," he said.

The rental market for commercial real estate in Petaluma, which is home to all but one of the acquired properties, has shown recent signs of recovering from the collapse of the tech boom.

In 2009, office vacancies hit a high of about 42 percent in the city, but they have been trending down since.

At the end of 2011, they reached 31.3 percent, according to estimates from Keegan & Coppin, a Santa Rosa-based real estate firm.

The improvement follows a flurry of buying and selling of commercial property, much of it at rock-bottom prices, said Al Coppin, president of Keegan & Coppin.

Last year, Basin Street Properties, a development firm founded in Petaluma, reacquired eight buildings that it sold six years earlier to Equity Office Properties for a quarter of the price it sold them for.

Similarly, PB&J and Investcorp bought their properties for about $20 million less than their assessed tax values, according to public records.

Such bargains have resulted from large institutional investors, such as Equity Office, which boasts 70 million square feet of office space in its portfolio, and RNM, which was established by a co-founder of Oracle Corp., deciding to put their money elsewhere, Coppin said.

"They are selling them at wholesale prices just to up and go on to the next thing," he said.

New owners motivated to bring in tenants have helped to bring down the vacancy rate, he said.

But the bargain purchases also have rocked values in the commercial market as a whole.

"It creates a problem for the equilibrium of real estate valuations," he said, although he said he sees it as a passing phenomenon.

Most large institutional investors already have left the market, he said.

"The smart guys are like PB&J," he said. "These guys have all done very well."

You can reach Staff Writer Sam Scott at 521-5431 or at sam.scott@pressdemocrat.com.