Loudoun County supervisors have decided to delay their vote on new land-use rules for as long as three weeks, citing the sheer size of the effort to overhaul the county's zoning ordinance.

Supervisors finished initial deliberations Monday on the dense legal document that governs what can be built in Loudoun and where. But they left one of the most difficult decisions -- to whom the law will apply -- until next Monday, the day they had originally planned to vote on the final draft of the new regulations.

Supervisors said the finished product probably won't come to a vote until after Christmas.

Several supervisors said they needed more time to make sure that the new law, the culmination of three years of sometimes vigorous debate, is faithful to their vision.

"We just want to see that the final product reflects what we think we've done," said Supervisor Jim Burton (I-Mercer).

Board Chairman Scott K. York (R-At Large) said the vote would probably be taken at the end of the month or early next month, though no later than the board meeting scheduled for Jan. 6.

York said a crucial outstanding issue is exactly who should be exempted from the strict new regulations through a "grandfathering" clause.

Officials must decide how to handle the large numbers of home-building applications submitted to the county in recent years. About 4,000 applications, mainly for subdivisions, have been submitted over the past five years, said Terrance Wharton, the county's director of building and development. Officials said the rush has come since the election of eight supervisors in 1999 on promises to slow growth.

Some officials see the bulk of those applications as an attempt to make an end run around the strict new rules proposed by the county. They said no special allowances should be made for applicants who may have submitted projects under one set of rules only to have the rules change dramatically next month.

Other officials advocate grandfathering all applications submitted up to the time the new zoning ordinance is adopted, a policy that would be more lenient than required by state law.

Under Virginia law, applicants have irrevocable "vested" rights to develop their property if they have met a series of legal standards, such as whether a local government has given them certain approvals and whether a landowner or developer has moved ahead with the project based on those approvals.

"I think there's a reasonable time period and an unreasonable time period," York said. "I will probably push for as strict as possible."

Some landowners said they were relieved they had gotten their projects through in time. Lawrence V. Phillips said that subdivision plans for his 700 acres near Round Hill were recently approved but that many landowners were too slow and had lost their chance.

Burton argued that many landowners had "abused" aspects of the rules to slip in questionable applications.

"The whole grandfathering decision sort of festers to the last day," said Peggy Maio, a representative of the Piedmont Environmental Council, who said last-minute lobbying and politicking on the issue is a staple of such land-use fights.