Early last year, Michael Weiss began attending tenant board meetings at the Brooklyner, Avalon Fort Greene and a handful of other luxury residential towers in downtown Brooklyn. In October, Mr. Weiss, director of the MetroTech Business Improvement District, threw the group's first neighborhood block party on Bridge Street, with live music, rides and food. He is now organizing a community stoop sale on Lawrence Street that's scheduled for May.

“We've got to keep our focus on new residents,” Mr. Weiss said. “They're essential to our area's growth.”

True, but that wasn't the intention when the Department of City Planning approved a comprehensive redevelopment plan for downtown Brooklyn in 2004. What it envisioned was a commercial district full of glittering office towers. But downtown has become the borough's fastest-growing residential neighborhood, and local officials are adjusting.

“We were supposed to get the third-largest business district in the city [behind midtown and lower Manhattan],” said Robert Perris, manager for Brooklyn's Community Board 2, which includes downtown. “What we've gotten is a high-rise residential neighborhood.”

Filling up

Since 2004, the area has seen the addition of 23 residential buildings with a total of more than 4,300 units, according to the Downtown Brooklyn Partnership. They range from condominiums in the Williamsburgh Savings Bank building, a mixed-use project co-owned by basketball legend Earvin “Magic” Johnson, to rental apartments in the Brooklyner, which in 2009 became the borough's tallest building. Another 1,000 units are under construction, according to the partnership.

Many projects are filling up quickly. Dklb Bkln, a 36-story, 365-unit rental building on DeKalb Avenue where one-bedroom apartments can fetch almost $2,800, is now 97% occupied, according to a company spokesman. Similarly, only seven of 246 condos remain available at be@schermerhorn, on Schermerhorn Street; two-bedroom units there have sold for as much as $829,000.

“One of the components of a healthy downtown is having a 24/7 community with a vibrant residential sector,” said Joe Chan, president of the Downtown Brooklyn Partnership. “We're delighted.”

Not everyone is thrilled.

City Councilwoman Letitia James, who represents large sections of the downtown area, argued that the boom has excluded low- and middle-income families. She also noted that the neighborhood lacks schools, food stores and other necessary services and amenities.

“We were sold a bill of goods,” Ms. James said. The residential component should have more affordable housing, she added, but what she most wants to see is the thriving commercial center that the city initially proposed.

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