Those who enjoy Brooklyn’s serenity should watch out – it might soon end. The Corcoran Group predicts that the home of Coney Island, the Brooklyn Bridge, and Junior’s cheesecake will see 35,000 new condominiums built in the next three years.

By 2007, the real estate firm estimates thousands of apartment buildings will crowd the borough, with the bulk gathering at the Williamsburg and Greenpoint waterfront. The firm’s development group spent months deriving this figure using an adhoc method of driving through the neighborhood, searching out construction sites, reading building permits, and researching the city’s Department of Building’s Web site. It also estimated building densities that could be constructed over time on empty lots by looking at the zoning.

“I went block by block reading building permits and marking up a zoning map in my car,” the director of development sales for Corcoran, Eric Brody, said. “We don’t want to release the report to the public because it is proprietary, and we hope we will be hired because of its information,” he added.

Despite the report’s secrecy, the Corcoran Group made a PowerPoint presentation of its findings to a group of developers, agents, and politicians at the Brooklyn Borough Hall earlier this month at a meeting hosted by Brooklyn Borough President Marty Markowitz.

Because of the Veterans Day holiday, Mr. Markowitz was unavailable for comment.

The first batch of apartments is the nearly 20,000 units to be built in Greenpoint and Williamsburg within the next three years, including 246 Withers St., the Schaefer Landing’s development, and the Gretsch Building. Some of the buildings have already sold out, and agents, including those at the Corcoran Group, have been overwhelmed by demand as the buyers’ profiles change from hipsters and artists looking for cheap rents to families in search of luxury living on the water.

The waterside developments are selling for an average of $650 to $800 a square foot while near Bedford Avenue, the main commercial artery that runs through the area, real estate is selling for $550 to $800 a square foot, Mr. Brody said.

The area of Park Slope on Fourth Avenue between Warren and 15th Street, known as the Fourth Street Corridor, will also experience a building boom, with Mr. Brody and his team estimating some 3,000 apartments built in the next three years. The city’s Department of City Planning intends to upzone the area to allow for buildings with more than 100 apartments, even as it plans to downzone the rest of Park Slope to preserve its historic character. Already, a building at the corner of Fourth Avenue and Fifth Street with roughly 150 units is under construction, Mr. Brody said. However, some environmental problems could delay construction in the neighborhood, Mr. Brody added.

With the Department of City Planning rezoning the area for residential development, a new Brooklyn Bridge Park, and the likely conversion of the Watchtower Bible and Tract Society building into condos, Downtown Brooklyn and the Atlantic Avenue corridor are other areas ripe for development, with the likelihood of up to 9,000 new residential units by 2007, Mr. Brody said.

Red Hook, with the opening of the Ikea furniture store and the Fairway Market, will also see an influx of over 1,000 apartments by 2007, while Vinegar Hill and DUMBO will receive 1,410 units, according to the Corcoran report.

In the long term, Mr. Brody expects the area surrounding the Gowanus Canal to be developed, although much of that neighborhood remains zoned for manufacturing. The area from Third Avenue and Nevins Street to Red Hook “is a long-term investment for a developer willing to buy now and hold it for the long haul,” Mr. Brody said. “Most developers think in the short term, with a mentality of buy, build, sell, so it is not easy to convince them to buy these plots yet,” Mr. Brody said.

Despite the lack of investor interest, the surrounding areas have been closing in. An old church and some parking lots along Atlantic Avenue have been converted into a residential development, and the fashionable Carroll Gardens neighborhood has already spread toward the Gowanus Canal with some development along Baltic Street, “so it is happening whether the developers are ready for it or not,” Mr. Brody said.

“Some residents are nervous about all this development, but it is all good news for property value because developers are not going to glut the market, so prices will only increase,” Mr. Brody said.