Thomas, the sixth Lord Fairfax, certainly never imagined that an office tower would be built next to the 18th century hunting lodge he built in what is now the Virginia suburbs.

His Ash Grove estate, of course, was planned before a commercial building boom hit the nearby Tysons Corner area. Now some Fairfax County residents fear that high-rise development has become a 20th century threat to the lodge because a Vienna man who owns land next to the lodge wants to rezone his property to permit such construction.

James C. Richards and his mother, Helen M. Richards, who own 3 1/2 acres about 300 feet from the 240-year-old lodge, want Fairfax County to zone their residential property for industrial uses. They want to attract developers to the site, located in the 8800 block of Ash Grove Lane near Rte. 7 and the Dulles Airport Access Road.

The county planning commission last week voted 6 to 1--with one abstention--against the request. County supervisors, who have the final say over the proposal, could overturn the decision when they consider the proposal April 12.

"I'm guardedly optimistic," said Wilson C. Sherman, whose family now lives in the Ash Grove lodge his ancestors purchased from the Lord Fairfax family in 1850. "But you never know what people will do. Ash Grove is a home of historical significance. I just hope they don't allow the setting to be ruined."

The Richards' lawyer, Russell S. Rosenberger Jr., down-played concerns that any development would encroach on the Shermans' home. "The property is far enough removed from the house to provide adequate protections," he said. "I think Lord Fairfax was one who was for progress."

County historians say the hunting lodge dates back to the 1740s when the Fairfax family moved their principal residence to Northern Virginia from downstate. Soon after, in June 1742, they helped pursuade the state legislature to split part of the area from Prince William County and declare it Fairfax County.

The house, which is located on 43 acres of wooded land, has since been listed as one of Fairfax County's historical spots. In recent years, as commercial development has spilled over from the Tysons Corner area, prices for land in the area have skyrocketed and put pressure on property owners to sell to developers.

The Shermans' have lured some of the development near their home. Several years ago Wilson Sherman sold part of Ash Grove to allow developers to build a Sheraton Hotel near Rte. 7. The Russells' lawyer strongly objected to the sale.

"It's easy for them to cry for historical preservation when they've already got theirs," said Rosenberger, referring to the one-third interest the Shermans' have in the 21-story Sheraton. "They want to draw the line now that they've got their money from the hotel."

Rosenberger added that even if the Fairfax lodge were declared part of an historical district it "would not prohibit industrial development" on the adjacent land.

The Shermans' lawyer, Edgar A. Prichard, argued at the Planning Commission meeting last week, that the sale was undertaken to produce enough income to keep the rest of Ash Grove intact.

Mayo S. Stuntz, a member of the Fairfax Historical Society who testified as a private citizen against the rezoning voiced what he said would have been the sentiment of the man who planned the house. "You have to preserve the setting," said Stuntz. "I don't think Lord Fairfax would want an office building 300 feet from Ash Grove."