H. S. Bogan Jr. said the three-story building he owns at 308 East Capitol St. is a condominium.

The certificate of occupancy on file with the D.C. government says the building is supposed to contain rental apartments.

But on a recent typical morning, business-suited, white-collar professionals carrying briefcases arrived at the building to start their work days instead of leaving it for jobs elsewhere. As it turns out, the brick building at 308 East Capitol is being used as offices by several businesses, according to two Capitol Hill real estate agents.

When asked about the offices in his building, Bogan said, "I cannot discuss that with you."

All over Washington -- but particularly on Capitol Hill, in Georgetown and around Dupont Circle -- owners of residentially zoned buildings are renting space to companies and associations for use as offices. Businesses rent the residential space, according to neighborhood residents and real estate agents familiar with the problem, because they can get such space for about half the cost of renting commercial office space.

They also do it, say the residents, because the D.C. government has thus far been unwilling to crack down on such office uses.

"Two years ago, the Residential Action Coalition submitted a list of over 100 such zoning violations to the city," said Anne Sellin, a member of the coalition's zoning committee. "The city acted on only one, a porno business that was too close to a special-use zone."

On Capitol Hill, a group of developers has compiled a list of what it says are at least 150 cases of office use of residential space, some of which it has been complaining to the city about for years. The developers put together the list by locating Capitol Hill associations and businesses listed in the Yellow Pages on the city's zoning map to see how many were outside commercially zoned areas.

"The lack of enforcement makes a mockery of the zoning code," said William Frank Reed, a D.C. attorney and local developer. "The city spends an immense amount of money on developing a comprehensive plan and zoning maps, but when they don't enforce it, the people say the hell with it and rent residential apartments."

Stephen McCarthy, zoning enforcement chief for the city, said he could not discuss specific cases, including the office space in the residentially zoned building at 308 East Capitol St. The D.C. Office of Consumer and Regulatory Affairs said it is unable to compile a list of the number of zoning violations prosecuted by the city in the past five years because the office does not have an automated records system.

Residents on Capitol Hill, who have been badgering the city about such problems for as long as 10 years, said they doubted whether the city had prosecuted more than a handful of violators. The few cases they are aware of are instances in which citizen groups pushed the city to correct a violation, one of which took five years.

Reed, who recently developed a small office building at 317 Massachusetts Ave. NE, said that he has had trouble finding any tenants for his building, primarily because tenants can easily find space in residential buildings to lease for half what he is charging for space in his building.

Reed said he would lower his rents, but that with the cost of construction and borrowing money, he has found it impossible to do so.

Larry Monaco, president of the Capitol Hill Restoration Society, said that the problem of office encroachment has been present for years but has worsened in the last two years, as rents for properly zoned offices have increased.

"It undermines the residential fabric of the community and drives up residential rental rates," Monaco said. "It also undermines commercial property in the area, because the illegal buildings rent for so much less."

One Capitol Hill real estate agent, who asked not to be named, said that he estimates properly zoned commercial office space rents for between $18 and $22 a square foot on the Hill. Office space in residential buildings, however, usually rents for about $9 a square foot.

"It's more than the owner would get from renting it as residential," said the source. "They don't seek variances to make it legal because then they would have to conform with fire codes and things. Since the city doesn't enforce the zoning code, why should they jump through all those hoops?"

Developers who do jump through the hoops to build office space in commercial zones, however, say they are angry that the city is so tough on them and so lax with the owners of residential buildings who rent them as offices.

"The city was very efficient about raising my taxes to reflect the new use for my building at 317 Massachusetts Ave., even before I had a single tenant," Reed said. "I'd like to see the same degree of efficiency in enforcing the zoning code so I could get some tenants."

Richard Wolf, chairman of the planning committee of the Capitol Hill Restoration Society, said that wherever commercial and residential uses exist "cheek-by-jowl," as they do in many areas of Washington, the problem will exist. He also said that continued illegal use creates an atmosphere of commercial uses in residentially zoned neighborhoods, which some citizen groups fear could produce pressure to have some areas rezoned to commercial.

In the Logan Circle area, resident Thomas Lodge said he notified the city about an improper use 12 months ago but that the city has never visited the building.

"It's happening everywhere on the periphery of downtown," Lodge said. "At lunch, the office workers come sit on the steps of the houses to eat their lunches, because they don't feel safe in the parks and there's no place else for them to go because this is a residential area."

A bill passed by the D.C. City Council last spring, which will become law sometime during the next month unless Congress moves to block it, allows the city to prosecute zoning violations as civil instead of criminal activities, a change the city says will make it much easier to move on improper office uses.

The bill does not, however, "decriminalize" the zoning code, but instead allows the city to choose either civil or criminal prosecution for zoning violations.

Criminal prosecution, city officials say, requires a ponderous legal procedure, including taking the case through the crowded court system. Civil prosecution will allow the city to issue citations and levy fines through a hearing administrator rather than the courts.

Those calling for more enforcement said they were hopeful that with the change in the law the city would have to act on more complaints, but questioned whether there would be enough enforcement workers to do an adequate job.

"It you don't have the enforcement people, it will just be chaos," said Wolf. "There are so many places where this is happening, it's going to take them months to put it together, even if they get a full staff."

Some residents, however, say they think the city should still prosecute some zoning violations as criminal cases, to let owners of residential buildings who lease office space know the city is serious about the problem.

"This kind of thing feeds on itself," Wolf said. "If the city would move against just one violator, 25 others would stop doing it. People need to know the city will prosecute, or else they'll continue to do it."