The town of Chevy Chase, a prosperous enclave in Montgomery County, voted unanimously last night to adopt a six-month moratorium on the demolition of houses, construction of homes and large-scale renovations.

Even as builders prepared lawsuits to challenge it, the town's five-member council adopted the measure to allow time to consider ways it might control "mansionization" and its effects in the 1,032-home neighborhood where Cape Cods, colonials and the occasional 1970s-era rambler are rapidly being replaced by houses two or three times as large.

"It's important to send a signal to developers that a lot of people in town don't want these big mansions built," said Mayor William H. Hudnut, a former mayor of Indianapolis and an urban planning expert.

While communities across the Washington region are experiencing the same pressures from development and the real estate market, Chevy Chase is among a few jurisdictions to impose such a moratorium in recent years.

The measure includes an exemption for economic hardship and accidents such as a fire and excludes smaller additions. It would not affect projects for which town building permits have been issued.

There is only one application in the town's pipeline that would be affected, involving a tear-down and the construction of two homes. But builders say many more plans in more preliminary stages could be stalled.

"$160,000. That is the additional cost we anticipate we will incur by waiting for the moratorium to run its course," said Douglas Monsein, a builder who is under contract now to tear down one house and build another. "I'm empathetic to residents' concerns, but I think this moratorium is a poorly thought-out overreaction to issues that could be resolved."

Monsein said he plans to file a lawsuit today.

At last night's hearing, some residents and builders criticized the proposal as a blatant violation of their property rights and an attempt to regulate taste, but about 100 residents applauded the vote as a victory of community interests over developers' profits.

"The best way to protect our own property values is to retain the distinct character of Chevy Chase and not turn into another Potomac," Richard Ashford said.

In Montgomery County, officials are debating whether to change the way residential building heights are calculated and whether to reduce the maximum height from 35 to 30 feet in the southern part of the county. Arlington County officials are considering legislation to reduce the amount of lot that can be covered by houses, driveways and other structures.

According to Chevy Chase town records, 55 houses have been demolished since 1997. Many more have been substantially renovated, and it is difficult these days to find any block that does not have at least one house under construction, wrapped in silvery Tyvek with a porta-potty on the front lawn. Some blocks have been almost completely rebuilt.

Town residents have complained that the new houses hulk over their older neighbors, create drainage problems, force the removal of mature trees, and, in general, ruin the "special character" of the neighborhood -- an elusive quality that has to do with shade, scale and what one resident described as a certain "shabby chic."

Builders, and some new residents, argue that houses being torn down are often moldy, antiquated eyesores that are too small to be useful and that the new, larger homes -- which range from 3,000 to 7,000 square feet -- are improving the neighborhood as they increase its real estate values.

With the moratorium adopted, the town no longer will accept permit applications involving demolitions or substantial tear-downs, defined as projects that would demolish more than 50 percent of the exterior walls of a house. For six months, the town will not accept applications for substantial renovations, either, defined as additions whose footprints exceed 500 square feet.

During that time, the town will not permit removal of trees greater than 48 inches in circumference unless they are hazardous or diseased. The moratorium also increases the fine for cutting down such trees without permission from $250 to $1,000.

A newly built home towers over its neighbor on Walsh Street in Chevy Chase. Builders defend the new homes, saying they increase property values.