They were Montgomery County's answer to cookie-cutter subdivisions and isolated neighborhoods.

"Floating zones," as loosely defined by planners, are meant to free developers from the constraints of traditional suburban zoning. The results, at least on paper, are unique communities with diverse housing stock, amenities and retail space.

Since their inception in the late 1960s, the zones have been used to build new neighborhoods in Germantown. They also have served as a tool to revitalize older suburban town centers in Silver Spring, Bethesda and across the country.

But recent events in Clarksburg, where hundreds of homes were constructed in violation of building codes, also suggest that floating zones are much like they sound: vague, unpredictable and difficult to manage.

An estimated 80 percent of upcoming residential development in Montgomery will be done on the basis of floating, or "site plan" zones. The situation in Clarksburg, which is the subject of multiple state and local investigations, has county leaders scrambling to correct what they view as serious management shortcomings in the system.

"There was no conductor, and when you don't have a conductor, it's a recipe for bad things to happen," said County Council President Tom Perez (D-Silver Spring).

Traditional zoning laws establish specific rules for land use that usually can be changed only by lawmakers. Residential, commercial, industrial and agricultural zones all come with rigid standards for the type and amount of construction that can occur. The regulations leave little leeway for interpretation and require only casual oversight from planners.

Floating or site plan zones grant developers and county officials broad authority to negotiate the shape of a neighborhood. Although builders often push for greater density to maximize profits, planners tend to seek open space, retail and affordable housing. The result of the negotiations is a legally binding document called a site plan.

But the complexity of site plans creates a management challenge for county officials. Follow-up and enforcement can be time consuming.

"There is certainly a lot more work to review a project like that instead of one where everything is laid out specifically in ordinance," said Charlie Loehr, director of the county Department of Park and Planning.

There have been warnings about Montgomery's increasing reliance on floating zones. In 2003, a Denver consulting firm said the county's zoning ordinance was "one of the most difficult to use and understand" it had seen.

The report by Clarion Associates also said that "there is too much negotiated development with little guidance" and that "procedures and review processes routinely employed by staff are not reflected in ordinance."

In Clarksburg Town Center, a group of residents grew upset with the developer, Newland Communities, over what they viewed as a failure to follow plans to provide grocery and other shopping. As they investigated how their neighborhood was built, they discovered that hundreds of houses were built too tall or too close to the street. 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.

The planner, who contends that she was stressed and overworked, had been given the authority to amend a site plan after it was approved by the board. Newland Communities contends the planner exercised that authority.

Some planners say the county's recent growth has hampered its ability to plan in a rational way.

"The workload never decreases for the staff," said Joe Davis, former chief of the development review section of the planning department, an offshoot of the board. "You have a reviewer asked to comment on projects that are ongoing, and they last a long time. All the while they have new projects coming in the door."

Clarion made recommendations to county officials, among them that they codify unwritten procedures used by planning staff in reviewing developments, and that they draft more specific standards to be included in zoning laws. When it came time to implement many of the recommendations, however, Davis wrote to the Planning Board that staffing shortages made that impossible. He said that a fourth of the staff positions in the 30-member development review section were vacant in fall 2002.

Council members were furious this summer to learn that staffing problems remained and said they should have been told long ago that the Park and Planning Department needed additional support. On Tuesday, Derick Berlage, chairman of the Planning Board, is expected to ask the Council for more than a dozen additional staff positions to implement the zones and enforce the site plan agreements.

Civic activists, however, say the flaws in site plan zones go beyond adequate staffing. Some wonder whether they foster inappropriately close relationships between developers and planners. When discrepancies arise, as was the case in Clarksburg, they fear the developers are, more often than not, given the benefit of the doubt.

"This is all done in a vacuum because generally the citizens have no clue what is being proposed," said Norman Knopf, an attorney for the Clarksburg Town Center Advisory Committee, which uncovered the building violations in Clarksburg. "It's a blank check for the developer to have professionals constantly addressing the situation . . . constantly lobbying."

Developers downplayed suggestions that they lobby or pressure planners but said close working relationships are formed during the creation of site plans.

"You are down there every day. You know them. You work with them. You respect them," said James A. Soltesz of Loiederman Soltesz Associates, a development engineering and planning survey firm.

But Soltesz and current and former planning officials strongly dispute suggestions that the systems gives a built-in advantage to developers.

"It's a professional planning staff, and they exercise their professional judgment and they are constantly interacting with citizens, lawyers and environmentalists," said Gus Bauman, a former county Planning Board chairman.

Nevertheless, planning officials are hoping to build additional safeguards into the system to address any appearance that developers enjoy too much access. Loehr temporarily revoked planners' ability to make staff amendments to site plans last month until he can review the practice.

And Berlage said he intends to look for ways to make sure "planners take input from everyone, not just people seeking to build."

Underlying the situation in Clarksburg is an increasingly politicized fight between county agencies over who is responsible for enforcing a key feature of site plans, the height and setback rules.

The county code indicates that it is the Department of Park and Planning, operated by the Planning Board. In the mid-1990s, the department received authority from the county and state to issue fines if the site plan agreements are violated.

The planning department says the Department of Permitting Services, overseen by County Executive Douglas M. Duncan (D), is responsible for heights and setbacks once structures are built.

The dispute will be a focus of a County Council hearing Tuesday. Until the matter is sorted out, Duncan has halted the issuance of building permits for projects that require site plans.