The mood was subdued one recent evening when about 100 representatives from Arlington's various neighborhood associations gathered in a hospital auditorium to discuss one of the county's most controversial development proposals in years.

With little debate, the Arlington County Civic Federation voted to oppose the county's latest proposal to limit the size of large-scale homes, or so-called McMansions, cropping up in neighborhoods. The resounding "no" vote from one of Arlington's most powerful civic organizations reflects the dissatisfaction that many residents feel about the proposal to regulate home size, said Martha Moore, an activist who helped to analyze the proposal for the federation, which represents 83 civic groups. Views range from residents who think the county should not further limit home sizes to those who think restrictions should be tighter, Moore said.

Given the wide variety of opinions among residents and the development community, county officials are expecting an intense public debate when the County Board takes up the matter next month after years of study, proposals and counterproposals, board Chairman Jay Fisette (D) said.

"We're doing this in response to citizens' concerns," Fisette said. "They have been petitioning us to address the increase in oversized homes, the loss of trees and the impact [those homes have] on the character of their neighborhoods. This is not unique to Arlington, but the dilemma is real here."

In recent years, the demand for bigger, new homes and the lack of land for building in close-in Arlington has contributed to a boom in "infill" development, where smaller, older houses are razed for new construction.

Some residents in brick or wood bungalows who suddenly have found themselves living next to mega-houses have long complained that the larger structures block their light, create storm runoff problems and reduce property values.

The county even created a slide show of some of the worst offenders. Many of those homes have become known by such nicknames as "the Sycamore Street house" or "the Hacienda house."

News that a 12,500-square-foot house was planned just feet from their bungalow in Lyon Park "turned our lives upside down," said Karen Tober, 47, an Internal Revenue Service employee.

The house, in the 3100 block of Pershing Drive, often is cited by county officials as an example of the kind of structure that the proposed regulations are meant to prevent.

When completed, the five-bedroom, eight-bathroom house will have a basement ballroom with bar, indoor swimming pool, hot tub and library. The house, being built by restaurateur Yogi Dumera, will be more than four times the size of the average house on the block, county planners said.

"The people moving in seem like really nice people, but the house is too big," Fisette said. "It's out of scale for the neighborhood. It doesn't belong here."

But Dumera said that the home is his dream house, the culmination of nine years of planning for "spacious rooms" for himself, his wife and four children. The house is allowable under zoning conditions.

"I'm within my rights and doing what I need to do," he said. "I'm not disturbing anybody." He said he made an effort to speak with neighbors about their concerns but heard only from the Tobers. He eventually bought their home from them; they moved a short distance away.

Developers -- led by builder Terry Showman -- have vigorously opposed the county's proposal through newspaper ads and fliers, as have many residents who fear that tighter restrictions could hurt property value.

Many residents said they have been confused by three versions of limits that the county has proposed just this year.

"It's ridiculous and very complicated," said Francoise Adams, a retiree who lives in a small, three-bedroom ranch house in North Arlington.

Adams recently wrote a letter to the County Board opposing the plan, which she said she fears will diminish the value of her property by limiting the size of future construction on her lot. She estimates that if she or a future owner wanted to raze her house and rebuild on the same lot, under the proposed guidelines, the new home, driveway and outbuildings could cover only 4,500 square feet of the lot, compared with 5,800 square feet now.

Do county officials "think Arlington residents are stupid enough not to realize this so-called 'third option' is as bad as all the previous ones?" Adams wrote.

The most recent proposal from county staff members is that Arlington restrict the amount of land that a main building, driveway and outbuildings could occupy on a lot, according to a sliding scale based on lot size. The restrictions, however, would apply only to new homes and substantial renovations that involve tearing down more than half the exterior walls. The sliding scale ranges from 56 percent for lots smaller than 5,000 square feet to 35 percent or 8,000 square feet -- whichever is larger -- for lots of at least 20,000 square feet. The majority of homeowners would be restricted to building homes that would occupy around 2,100 square feet or 35 percent of their lots, whichever is larger.

If the County Board approves the proposal, Arlington will be the first major jurisdiction in the region to have such restrictions. Officials in Fairfax and Montgomery counties have studied the issue but, like Arlington, have been slow to enact limits. The Chevy Chase Town Council passed a six-month moratorium on new construction in August, aimed at controlling McMansions. A local builder recently challenged the move in court -- and won.

Longtime supporters of limits in Arlington emphasize that if nothing is done, residents will see more and more big houses mushrooming.

Under current guidelines -- which allow the main building, garage and driveway of a home to cover 56 percent of a lot -- "there is potential for great mischief to be done," said Robert Swennes, vice chairman of the county's Neighborhood Conservation Advisory Committee, which supports the limits.

Few homes in Arlington have reached that mark, "but a few developers have pushed that limit in recent years, and the adverse results are apparent to pretty much everyone," Swennes said.

The goal, Swennes said, "remains to eliminate for the future the most egregious examples of infill. . . . Not to eliminate infill or large houses, but to eliminate the 5 percent of infill that could potentially trigger a radical change in the character of the neighborhood in years to come, diminishing the value of adjacent properties."

The Arlington County Planning Commission is set to weigh in on the proposal Nov. 7. The County Board will discuss the plan Nov. 15, although the matter could carry over to one of two overflow meetings Nov. 16 and 29.

Fisette said the vote will go forward next month.

"We will decide it this year," he said. "There's every commitment by board members to do this."

Residents can calculate their lot coverage on the county's Web site. Go to:

Remodeled homes dwarf smaller structures in many parts of Arlington County. The county, which plans to vote on house-size restrictions next month, even created a slide show of some of the largest "offending" houses. Wayne Kubicki speaks at an Arlington Civic Federation meeting.Developer Terry Showman has led opposition to the proposal.Arlington planner Jim Snyder discusses lot-coverage issues.Residents' opinions about a proposal to restrict house sizes vary widely in Arlington County, where "McMansions" rise next to bungalows.Martha Moore of the Arlington County Civic Federation, which opposed the county's proposal.Chairman Jay Fisette (D) says the County Board is expecting intense public debate about size limits.