As a developer of commercial buildings, Ellen Sigal has a reputation for putting together unusually complex details in a unique way.

The 37-year-old businesswoman is completing her first large office building in McLean, which Mutual Benefit Life Insurance Co. and others will occupy. She also is planning a commercial-residential structure in Georgetown and is working on the financing for a nine-story, 27-unit condominium building at 25th and K streets NW.

After nearly four years in the business of visualizing projects, acquiring sites, arranging financing and working with architects, builders and leasing-management professionals, Sigal already has a reputation for knowing the numbers -- costs and square feet. But she "also adds a respect for design and aesthetics," says architect Guy Martin, who, with David Jones, designed Sigal's Georgetown and West End projects.

James R. Hunter, executive vice president of the Braedon Companies which is handling the leasing of the three-story, 72,000-square-foot building at 6833 Beverly Rd., McLean, said Sigal was the "moving force" in putting the deal together from its inception. "She acquired the site, worked with the architect (Smith, Segreti and Tepper) on design, secured the financing and works with Sigal Construction in building the project."

As head of Sigal Development Corp., Ellen Sigal occupies a well-ordered office in a fairly new Georgetown building. Her husband Gerald, head of Sigal Construction Corp., is next door. His firm does all of her construction, and handles other building and remodeling projects.

Gerald Sigal, a civil engineer, formerly directed major construction for Tishman Construction Corp. The Sigal family moved to Washington in the mid-1970s when George Sigal was in charge of the restoration and new construction at the Foundry project for Inland Steel near Georgetown's waterfront.

The Sigals both grew up in Brooklyn, met when they were 15, and have been married 17 years. Ellen Sigal went to Brooklyn College, UCLA, Louisiana State and Rutgers.

"Most of my education was in political science, economics and history." she said. "And I did a lot of research. And marrying Gerry, I also did some buying and managing for Bloomingdale's. My father was a buyer of women's clothes in New York and my mother ran a store. I grew up in retailing. My sister is a fashion designer."

But Ellen Sigal gradually was drawn into a construction-related career that paralleled that of her husband. When the family decided to stay in Washington, she helped her husband set up his new business. "At first the office was in our home," she said. "I handled the books, the phones, went to meetings and took notes."

Sigal eventually became interested and set up her own business. She has developed her own fromula to analyze a potential project, and figures construction hard costs today at $55 a square foot and indirect (soft) costs at an additional $35 to $40.

"Smaller sites, such as the one next to the Biograph in Georgetown, are more expensive," Sigal said. "I like to think that my margin for error is less than 5 percent in costing out a project. Analysis is one key. And you've got to know zoning and the market, plus interest rates and how to deal with people."

Sigal describes herself as "thorough, methodical and able to obtain information and use it." She also is a compulsive reader of everything I can."

Is it a handicap to be a woman in a field traditionally dominated by men? "Not really," she said. "It's necessary to make people respect your ability and your knowledge. That's how you gain respect and confidence.I like to get things done."

The older of their two sons sometimes helps out in the office, she said, and they are both "supportive of our careers: we make certain to spend time with them in the evenings and on, weekends."

Ellen Sigal's new $2 million building in Georgetown will combine office, commercial and residential space. The project at 2833 M. St. NW has been previewed in Progressive Architecture, which said that the "mixed-use building in a landmark context and varied program by the manipulation of symbolic elements."

The magazine also noted that the Martin-Jones design includes a "classical fragment negotiates the corner and, again reduced, acts as an entry porch to the apartments on the side elevation, a response to the federal town houses nearby."

"Architects know now that I don't like boxes," Sigal said. "I'm cost-conscious but not just looking for the cheapest. I like a building to fit in, whether it be classical or contemporary. Pleasing aesthetics are a priority."

Sigal's architectural contribution also is evident in the new three-story, brick building in McLean, according to architect Robert Calhoun Smith. "She encouraged our firm to make it interesting in a quiet way. The two-story entrance and third-floor balcony designed by partner Thomas Tepper combine to give it individuality and also make it say welcome."