When the owner of a historic structure in Fairfax County neglects the building and allows it to deteriorate, county officials can do little more than watch it go. The county's 22-year-old historic preservation ordinance offers no guidance.

Since about 250 structures in Fairfax County were identified as historic in a county inventory nearly 15 years ago, about 27 structures, or 11 percent, have been lost to deterioration or development.

A group of six historic preservationists, bothered by such losses, is forming a private, nonprofit organization to advocate tighter restrictions for preserving historic buildings and to educate county residents and leaders about the historic resources they stand to lose.

The group, called the Fairfax County Heritage Conservancy, will hold a meeting for prospective members at 7:30 p.m. Wednesday at the Fairfax City Old Town Hall at University Drive and Main Street.

The conservancy hopes to reach beyond piecemeal efforts to preserve specific historic structures with a countywide agenda and strategies.

"There have been groups formed around a specific {historic} site, but there's been no broad-based group . . . which is unusual for a county as large and sophisticated as Fairfax," said Sally Oldham, a founding member of the conservancy.

"Our focus has to go beyond the Mount Vernon District, and go beyond McLean, and look at what we have in common," said C. Richard Bierce, a founding member who is also on the county Architectural Review Board, which examines development plans for historic districts.

The conservancy will "work against the fairly widely held presumption" in fast-growing Fairfax "that there's nothing left in the county to preserve."

As a private enterprise, the conservancy will be free to maneuver where government officials cannot. "They can buy properties . . . they can lobby to a limited degree, they can raise money, all of which we cannot do, and they can also take stands," said Elizabeth David, a county historic preservation planner.

The conservancy's initial goals include recommending ways for the county to strengthen the historic preservation ordinance, a task recently begun by county planners, and urging the county to create separate preservation guidelines for each of the county's 13 historic overlay districts.

"I think you have had a situation where . . . development without question has had the upper hand. There has not been a lot of consideration given to the historic," Oldham said. By tightening the historic preservation ordinance and the historic district guidelines, "you get decisions that are consciously made, as opposed to by default."

Although generic guidelines for historic districts exist, "each of the districts are different, historically. We really need different guidelines," Bierce said.

As for specific historic sites, the conservancy initially will focus on preserving the Huntley Mansion, a decaying early 19th-century residence south of Alexandria that the county park authority recently bought, and rehabilitating the oldest part of a county courthouse in the heart of Fairfax City that dates to 1800.

"These are very real buildings. These are very important buildings. They are a tangible example of what we're all about," Bierce said.

The courthouse is "symbolic of the county heritage," Oldham said. "If we can't take care of our 1800 county courthouse, it doesn't speak well of this community."