State officials approved a $5.2 million deal Wednesday to buy land in Santa Rosa for a new $178.7 million Sonoma County courthouse.

The state Public Works Board approved the agreement to purchase 6.8 acres of bargain-priced land from the county at its main campus north of Steele Lane. It includes the site of the former county jail, which was demolished in 2010.

On the old jail site, the state has proposed building a 173,500-square-foot, six-story court building that would replace the Hall of Justice next door.

That 47-year-old structure, state officials say, is outdated and undersized and cannot be renovated to serve court needs, including modern security features, larger jury assembly and deliberation rooms, in-custody holding areas and adult and children's waiting rooms.

The new facility will feature 15 criminal courtrooms, 450 above- and below-ground parking spaces and consolidated criminal, traffic, juvenile dependency and probate proceedings.

Construction is set to begin in early 2014 and be completed in early 2016, barring budget problems in Sacramento.

The first stage of work, on architectural design, is up for funding in the coming fiscal year. Jose Guillen, executive officer for Sonoma County Superior Court, said the project's budget is subject to possible reductions by the state Judicial Council, which is set to meet next Friday.

The Santa Rosa project is on a list of 41 courthouse renovation and construction projects statewide to be funded through bonds authorized in 2008 under Senate Bill 1407.

The project architect will be New York-based Richard Meier & Partners, the firm that designed The Getty Center in Los Angeles and the Barcelona Museum of Contemporary Art, among other notable structures.

The state purchase also includes the 3-acre county Fleet Building site on Ventura Avenue and a 1.3-acre parking lot on Russell Avenue, parcels to be used for above-ground parking.

The county agreed to sell the land for half of its appraised value. The discount was given because inmate transportation costs to alternative locations could amount to $3 million a year, court officials said.

County supervisors signed off on the deal late last year. Escrow is expected to close in mid June.

It's still undecided what will become of the old facility once the new courthouse is built.