The D.C. Board of Zoning Adjustment voted this week to allow a developer to refurbish a Capitol Hill carriage house facing an alley and rent it as an apartment, possibly setting a precedent that could lead to conversion of many of the 300 to 400 carriage houses on Capitol Hill.

While other carriage houses in the city have been converted from garages to other uses, zoning attorneys and citizens groups say they believe this is the first time a carriage house sharing a lot with a principal residence has been granted zoning variances that will allow it to be used as a dwelling.

The city planning office and council member John Ray had recommended that the board reject the proposal, saying that to allow conversion of carriage houses into apartments would increase the population density and create parking and safety problems in older neighborhoods.

While the board's 3-to-0 vote directly affects only one carriage house, at 642 E. Capitol St. NE, BZA members said they knew the decision could set a precedent and lead to a flood of similar requests from owners eager to redevelop their carriage houses on Capitol Hill, as well as those in other neighborhoods in the city.

The BZA, which granted four variances under the zoning code to allow the carriage house to be used as an apartment, said it did so because "the city needs more housing," in the words of BZA Chairwoman Carrie L. Thornhill.

"Because of the dwindling housing stock in the city, use of carriage houses for housing should take precedence over concerns about parking," she said.

Capitol Hill residents who protested the proposal said, however, that they will ask the BZA to reconsider its decision based on their belief that the panel improperly ignored "its own rules and the law" by approving the variances. If that action is unsuccessful, the residents said they would consider appealing the ruling to the D.C. Court of Appeals.

In a 1972 ruling, the D.C. Court of Appeals said that the BZA could only allow variances in cases where there were "unique circumstances peculiar to the applicant's property and not to the general conditions in the neighborhood."

The BZA, in making its decision, said the E. Capitol Street application was unique in terms of the size of the carriage house and the historic character of the building.

Residents of the area said, however, that there are at least five carriage houses of the exact same size in the immediate vicinity, as well as numerous others of similar size. In addition, they said that all the carriage houses on the Hill date from the same turn-of-the-century period and are protected as part of the Capitol Hill Historic District.

Larry Monaco, president of the Capitol Hill Restoration Society, called the BZA action "outrageous," and said the society probably would support an appeal of the decision.

"They are completely ignoring the case law and their own zoning rules about how they should go about granting variances," Monaco said.

Brad Snell, one citizen fighting to block the conversion of the carriage house, said, "The BZA made a zoning commission decision on this case. It was total usurpation of the zoning powers of the zoning commission and the D.C. City Council." Snell said the citizens would petition the BZA for a re-hearing of the case, and possibly appeal it to the D.C. Court of Appeals.

Fred L. Greene, director of the city planning office, said he was "concerned" about density in areas like Capitol Hill, but that the BZA was justified in considering the housing crunch in the city because the BZA needed a policy "framework" from which it could make decisions.

Carriage houses generally are two-story brick garages built behind row houses at the beginning of the 20th century as shelter for carriages and horses. The second stories usually were used as haylofts.

The D.C. zoning code prohibits use of carriage houses that do not sit on their own separate lots as residences through a series of restrictions on lot density and minimum size requirements for front and back yards.

BZA members Patricia N. Mathews, Charles R. Norris and Thornhill approved four variances to the zoning code that will allow the Historic D.C. Property Group Limited Partnership, IV to rehabilitate the E. Capitol Street carriage house into a luxury apartment. BZA member William F. McIntosh abstained from the vote.

The BZA, on a 4-to-1 vote two years ago, rejected a similar petition for a carriage house conversion in the same block. Thornhill was the single supporter of the previous case.

"My view is that in great degree the facts are the same between this case and the previous case," Thornhill said just prior to the vote.

Mathews said that because of the city's general policy of helping create more housing, the BZA "is obliged to take a fresh look at using carriage houses for housing."

Citizen groups protesting the conversion presented a petition with signatures of 75 nearby residents asking the board to reject the proposal. Advisory Neighborhood Commission 6A supported the proposal, but with the condition that the residents in the carriage house and the principal residence on the lot be prevented from parking in the alley.

Parking in the alley, and the possibility that cars could limit emergency vehicle access to the alleys, was a major concern for many of the persons urging the board to reject the proposal, along with concern that allowing conversions of carriage houses could create a parking crunch on the public streets of the Hill.

Robert J. Hummer, a principal of the partnership that owns and rents the property, said the owners were "pleased" by the outcome and would be starting reconstruction of the carriage house as soon as possible.