When Thomson M. Hirst of McLean discovered that 13 houses worth $400,000 to $500,000 each would be built across the street from his contemporary estate, he had one overriding concern: there goes the neighborhood.

The developer of the new houses is "just not respecting the individuality of the land," said Hirst, whose own home is valued at considerably more than $500,000. "It's just another piece of meat they're just going to chop up."

Approval for the 13 new single-family houses came Monday night when the Fairfax County Board of Supervisors voted to rezone 8.6 acres of land controlled by James J. Driscoll, a developer who lives in Potomac.

The decision left neighbors of the heavily wooded property, just inside the Capital Beltway, about a five-minute drive from Tysons Corner, worried that the character of the area is in jeopardy.

"The houses around here are very fine home on very large lots," said Lynda K. O'Bryan, a neighbor who led the charge against the Driscoll project. The neighborhood, she said, "is very nature-oriented, I guess you might say."

O'Bryan and others area said that their objections were not that the Driscoll houses are insufficient for McLean, but that they are too large for their lots. They also feared losing some fine old sycamores and poplars, and compromising the feel of the neighborhood.

"This is going to change the quality and character of our neighborhood," said O'Bryan. "Even we cannot adequately visualize what the property will look like once the bulldozers come in."

Many houses in the area are situated on one or more acres of land. Property values vary widely, from around $200,000 to nearly $1 million.

When the project was proposed in December, Driscoll asked for a 17-house project, but opposition from neighbors forced him to trim the size of the project to 13 dwellings.

Despite Driscoll's concessions, O'Bryan says she is afraid the project will set a precedent for other property owners who may try to amasss enough land in the neighborhood to build other similar developments. Under Fairfax zoning law, such developments can be built on any tract of more than five acres.

Some of Driscoll's adversaries in the neighborhood were developers themselves, well-versed in the art of turning a piece of land into a handsome profit.

"I've been on the other side of the fence," acknowledged Hirst, who has developed office buildings in Reston and along Shirley Highway (I-395).

Driscoll, who has put together a number of residential projects in Northern Virginia -- none as small as the one in McLean -- said the new houses "would be worth more than the houses that surround them."

Asked then to account for the din of opposition, he said: "I think the community was trying to achieve the lowest possible density [of houses]. I'll take it at face value."

George M. Lilly, chairman of the county planning commission, was philosophical about the opposition. "They're in an area where the houses are custom-built, and they got a notion that Driscoll was going to build a subdivision, and that upset them," he said.

Hirst, who has built a swimming pool and tennis court on his property, said one of his chief objections to the Driscoll development was that it "serves a narrow range of income types" and "ignored our plea for more economic variety."

Asked if that meant he wanted a greater number of cheaper -- and dearer -- houses to be built on the tract, Hirst said only that the issue needed to be studied. "We never said the price [of the new houses] mattered one little bit to us," he insisted. "We're motivated more by the creative process, and the developer is motivated more by profit."