The Board of County Supervisors has approved an addition to the Piedmont gated community outside Haymarket, expanding it by about 50 percent to allow for more than 1,200 homes.

The upscale development, which now will encompass 780 acres, is just one of many endorsed for the Haymarket area in recent years.

It sits between Route 15 and Interstate 66, offering houses from $300,000 to more than $1 million.

Like the 2,800-home Dominion Golf and Country Club, approved last month amid controversy over water supplies, and Heritage Hunt, the 2,000-home age-restricted community under construction, Piedmont joins an increasingly common club in the county's western end.

With sprawling, luxury developments, golf courses and private roads, the county hopes to create an elite atmosphere--all the more rarefied because it is near open space preserved under the county's "Rural Crescent" plan.

As supervisors and county staff target high-paying industries in the technology and bio-research areas, they hope white-collar employees who work in Prince William or the Dulles area will be drawn to the county's more expensive housing.

And a density reduction under the rezoning the board approved Tuesday lends respite to growth-weary supervisors eager to expand the tax base through high-price housing.

The tracts rezoned Tuesday, totaling 258 acres, had been designated agricultural, but the county's comprehensive plan allowed them to eventually have as many as 318 dwellings.

Under the developer's mixed residential rezoning, each single-family house will sit on one-half to 2.5 acres. At most, 232 houses will be built.