If Andrea Wenner had followed the career track pursued by most of her Columbia Business School classmates, by now she’d be climbing the ranks of a whiteshoe firm and cutting million-dollar deals over lobster thermidor at the Four Seasons.

Instead, Ms. Wenner’s office is hard to find — she occupies a corner room rented from a travel agency in a dusty Midtown building. She eats lunch either at her desk or brown-bags it in some of the Bronx’s toughest neighborhoods.

The good news these days is that these neighborhoods aren’t as tough as they used to be. If Ms. Wenner has her way, vast stretches of the Bronx, Brooklyn, and Harlem will continue a renaissance around the playgrounds that her not-for-profit organization, Out 2 Play, is building across the city.

“I was on the traditional path — I was supposed to go into real estate finance,” Ms. Wenner said as she arranged Styrofoam poster boards bearing architectural plans of current projects. “Instead I’m building playgrounds.” She credited her Entrepreneurial Greenhouse class at Columbia for inspiring her to consider a nonprofit career in the first place. She learned that starting any business requires the ability to talk to all types of people — from lawyers and financiers to the ordinary Joe on the street. That’s just what she began doing after her business school internship at a consulting firm that specializes in urban development.

One of the projects she worked on was Take the Field, a pubic/ private partnership of real estate developer Preston Robert “Bob” Tisch that works to refurbish football fields and baseball diamonds in city parks. Said Ms. Wenner: “I was living near an elementary school at the time and thought to myself, ‘Why can’t this be done on the primary school level?'”

She based her initial idea on the assumption that schools lacked enough open space to build good playgrounds for children, and asked: Why not renovate the rooftops of schools and surrounding buildings? What she discovered was that most of the city’s public elementary schools have surprising amounts of open space. “What they don’t have is the money to make these spaces into anything constructive for the students,” she says.

Although Ms. Wenner will never count out the rooftop playground option, she says she’s learned that Out 2 Play is more effective when it can act quickly in a neighborhood. Rooftop renovations are a lot more complicated, as engineering and legal concerns usually bog down such projects. In forming any organization devoted to social action and improvement, there are many learning curves, and Ms. Wenner points to her fair share. Perhaps the most significant experience for her was finding the most effective ways to bridge the gap between the public and private domains.

One of Out 2 Play’s staunchest allies is a congressman who represents the Bronx, Joel Rivera. “Once I knew I could count on funding from him, I started taking lists of possible projects to his office,” Ms. Wenner said. “From there, it was on to the architect.” The president of the Bronx, Adolfo Carrion Jr., is a sponsor of four current playground projects as well, according to Ms. Wenner. For now, Ms. Wenner is looking to hire a full-time program assistant as she starts looking into more renovation projects. Out 2 Play built 14 playgrounds this summer and has a dozen more projects under way.

Another advantage of having worked on a project that involved Mr. Tisch was that Ms. Wenner was already familiar with the group’s architect, Dan Margulies. He’s known for creating “recreation experiences” — translation for good playground designer.

“One of the best aspects of this job is going to the school’s principal and asking if he wants us to come in and revamp the playground,” Ms. Wenner said. “I haven’t met anyone who’s turned us away.”

Part of the initial success with Out 2 Play hinged on Ms. Wenner’s “Design Day,” a designation for an all-hands meeting of parents, school officials, architects, and construction executives. The school drives the design process, according to Ms. Wenner. For instance, at the Mohegan School in the Bronx, Mr. Margulies used an overall Native American design for the playground’s theme. All while listening to comments from the school’s 800 students as to what they liked best in an open space.

Of course, no construction project in New York City is ever easy, especially when it requires the nod of the local school board. But Ms. Wenner has a small army of volunteer liaisons who canvas neighborhoods and speed approval of Out 2 Play’s various projects. A new playground typically takes, from start to finish, up to eight months.

P.S. 156 in the South Bronx, for example, will soon open for the new school year to 750 students. Its new playground features a fully ramped, wheelchair-accessible play structure, tricycle track, kickball diamond, soccer, handball, and blacktop games. Until this year there was an empty asphalt lot.

Not too far down the road is P.S. 55, with 670 elementary school students, plus a middle school with 250 more. Its new playground has full-court basketball, a track, kickball diamond, handball, jungle gym equipment, and blacktop games.

Ms. Wenner’s six-person board of directors, filled with bankers and corporate executives, has the other crucial half of her organization covered: the Four Seasons power lunch set. It’s only with substantial private donations that Out 2 Play is able to create 40,000 square-foot playgrounds from scratch.

She estimates New York City has 250 public school playgrounds in need of renovation. At an average cost of $250,000, Ms. Wenner has some major league fund-raising ahead of her. She has 20 projects planned for 2008 alone.

After all this nonprofit work, might she eventually make the jump into the lucrative world of real estate finance? “I might down the line,” Ms. Wenner said. “But I’ve got plenty of time to do that. Right now I believe I’m making a difference.”