The Prince William County Board of Supervisors rejected yesterday an effort to exempt many building lots from a variety of county land-use controls.

By a 4-to-3 vote, the supervisors decided to stay with the county's present subdivision ordinance, which covers all building lots up to five acres in size.

Under the defeated motion, builders would have been exempt from controls -- such as building streets and roads to state standards -- on lots three acres in size or larger.

While the Prince William Builders Association said fewer controls would mean less costly housing for buyers, County Planning Director Jeff Middlebrooks told the supervisors that a looser subdivision ordinance would hasten development in prime agricultural areas. In a statement to the board, he said:

"... It will become more profitable [for builders] to forgo the minimum one-acre lot size and divide land for sale into three-acre lots with no state roads, no erosion control, no storm water management, no drainage improvements and no lengthy subdivision review."

Already, Middlebrooks said, 25 percent of Prince William's growth over the last five years has been in agricultural areas and outside the sectors planned and zoned for subdivisions. Such leapfrogging development takes farmland out of production and requires the county to extend costly services to isolated subdivisions.

In supporting a relaxed subdivision ordinance, Ed Jackson, representing the Prince William Builders Association, said "more controls mean more cost to the consumers... It's nice to have all these [controls], but a lot of them should be optional." However, Kenneth O. Thompson, a director of the Northern Virginia Builders Association, said his group was in favor of leaving the ordinance alone.

Jackson said builders have to wait 18 months to get their construction plans approved by the county. However, Middlebrooks said a recent study put the average time at seven months.

Supervisor Alice E. Humphries, who made the motion to keep the ordinance as it is, said: "You do not set standards for the best builder, you set standards for the worst builder... If it took 18 months to get a plat approved, something must have been wrong the first time it was submitted."

Supporting Humphries were Chairman Kathleen R. Seefeldt, Donald L. White and James J. McCoart. Voting to relax the ordinance were James Byrd, Andrew J. Donnally and T. C. Wood.