Montgomery County officials yesterday froze home building in most new subdivisions across the county while officials examine a variety of lapses in the once-vaunted planning process.

With County Executive Douglas M. Duncan and County Council members reacting to widespread building violations in Clarksburg Town Center, buyers waiting for homes to be built in Montgomery could face considerable delays and possible cost increases.

Duncan (D) and the chairman of the Planning Board have frozen the issuance of building permits in subdivisions that require site plans -- about 80 percent of pending residential projects -- until builders can verify that the projects meet height and setback requirements. Projects under construction can proceed, but those that have not broken ground will be subject to another review.

The freeze follows a move in neighboring Prince George's County this year to slow rural development and reflects widespread concern throughout the suburbs over the pace of expansion and accompanying congestion.

Duncan's announcement came an hour after four council members proposed a broader moratorium on new building permits until projects' site plans are thoroughly reviewed by county leaders. The council will vote on the emergency legislation, which would be in effect until winter, next week.

Combined, the two approaches represent a rebuke to a planning process that for a generation has tried to steer growth into designated areas near major transit routes. But at least in Clarksburg, one of the county's fastest-growing communities, officials have acknowledged that they were ill equipped to oversee that growth.

"The fact of the matter is the integrity of the planning process has been violated," said council member Michael L. Subin (D-At Large), a sponsor. "And this process has been one of great pride in the county."

In Clarksburg, a group of residents discovered this year that hundreds of houses in the town center were built too tall or too close to the street, and county officials say they never realized the problem. When the Planning Board held a hearing on those claims in April, a senior planner altered a site plan to reflect what had been built, officials say.

"A period of suspension is necessary to get better checks and balances in place and to reassign staff so we can have more eyes looking at things," said Derick Berlage, chairman of the Planning Board.

Developers and builders predicted dire consequences for home buyers and contractors, with the possibility of interest rates and housing costs creeping up.

"If you buy a house from me that I say I can deliver in six months, you can go out today and get a mortgage that will be good six months from now," said Tom Bozzuto, a developer with projects planned for Clarksburg and near Laytonsville. "If I don't know when I can start the house, you can't get a mortgage at all. You can't lock in an interest rate."

Duncan's freeze will affect about 200 building permits -- which could range from subdivisions of single-family homes to high-rise condominium buildings -- awaiting official approval in zones requiring a site plan. Applications will have to be resubmitted for further scrutiny.

Bozzuto, chairman of Bozzuto Homes, predicted that a slowdown will drive up the price of existing homes. "It's a supply-and-demand market, and the less supply there is, the greater the price people will be able to get for existing inventory," he said.

Already, efforts in place in Prince George's have slowed growth there significantly. In January, County Council members decided to stop accepting plans for new subdivisions in the county's most undeveloped region, known as the rural tier, for a year while leaders work on a comprehensive growth policy. That came on top of last year's legislation that links building permits to available police and fire services.

In Virginia, Loudoun County sought to slow development in its western reaches, only to have it struck down by the court.

If the Montgomery council's legislation is approved next week, residential building permits in areas requiring a site plan will be issued only after Berlage and Robert Hubbard, the director of permitting services, personally sign off on them. The council will then review the permit for 15 days, after which time building can start.

If a building permit has been issued but construction has not begun, the proposal requires that a "stop work order" be issued. The builder will have to reapply so that Berlage, Hubbard and the council can review it.

Subin and the other sponsors -- Nancy Floreen (D-At Large), Michael Knapp (D-Upcounty) and Howard A. Denis (R-Potomac-Bethesda) -- said home buyers should have to wait only a few weeks for building permits as long as the site plan conforms to Planning Board decisions.

But council member Steven A. Silverman (D-At Large) predicts that a backlog of applications for permits will ensue, delaying some projects for months. "It is unfortunate we have to take this step, but it is necessary to restore confidence," he said.

In Clarksburg Town Center, residents and county officials say the developer, Newland Communities, violated its site plan, which states that townhouses can be no taller than 35 feet. Newland officials contend that the planning staff gave them permission to build townhouses up to four stories, or 45 feet.

"County officials may be targeting the private sector as the whipping boy, but the officials who issued the plans and permits deserve an equal number of lashes, not one less," Newland spokesman Charlie Maier said. "No home in Clarksburg was built without their explicit approval."

Staff writer Ovetta Wiggins contributed to this report.