Residents of Capitol Hill have appealed a decision by the D.C. Board of Zoning Adjustment that they say sets a precedent for conversion of carriage houses from garages to other uses.

In a joint petition, the Capitol Hill Restoration Society and the Stanton Park Neighborhood Association this week asked the D.C. Court of Appeals to review the zoning board's decision to allow conversion of a carriage house at 642 E. Capitol St. NE from a garage to an apartment building. The zoning board voted 3 to 0 last December to approve the variances needed for the conversion.

While other carriage houses in the city have been converted before, zoning attorneys say that in the past such conversions have been allowed only for carriage houses that were on separate lots.

The zoning board's December decision was the first allowing conversion of a carriage house that sits on a lot dominated by a principal residence. Real estate agents have estimated there are 300 to 400 carriage houses on Capitol Hill that share lots with larger buildings and could now be converted under the zoning board's new precedent, as well as perhaps a hundred more in other neighborhoods in the city, such as Dupont Circle.

In their petition, the residents said that the zoning adjustment board acted "arbitrarily, capriciously, abused its discretion" and acted beyond its statutory authority when it approved the variances. The residents also said that the applicant, Historic D.C. Property Group Limited Partnership IV, failed to show exceptional and undue hardship or practical difficulty in requesting the variances, as required by law.

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

The zoning adjustment board, in making its decision on the carriage house, said the application was unique in terms of the size of the carriage house and the historic character of the building. BZA Chairwoman Carrie L. Thornhill said the variances should be granted to allow the conversion because "the city needs more housing."

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.

"They are completely ignoring the case law and their own zoning rules about how they should go about granting variances," said Lawrence A. Monoco Jr., attorney for the petitioners and president of the Capitol Hill Restoration Society.

Jacques DePuy, a lawyer representing the owner of the carriage house, said his client was disappointed with the citizens groups' petition for review.

"He is abiding by the legal process in seeking the authority to convert the carriage house," DuPuy said. "He is very unhappy about being pulled into court and all the expense."

Weissberg Corp. of Rosslyn bought two shopping centers in Warrenton, Va., for $14.9 million in January, and now plans to upgrade the facilities to encourage more expensive retailers to locate there for the expanding residential communities in Fauquier County.

The property, at the intersection of routes 17 and 29/211, includes the east and west plazas of the Northern Virginia Shopping Centers and 35 acres of undeveloped land zoned for commercial use. The two plazas have 50 stores and 250,000 square feet of commercial space. Weissberg plans to develop office buildings on the adjacent land.

The seller was the family of the late Dr. Aaron Gerber, who assembled the property over a number of years and built the west plaza in 1960 and the east plaza in 1979. The land represents one-third of the commercially zoned land in Warrenton.

"Our plans for modernization and renovation will make these centers more vital and appealing to the Washington metropolitan area residents who are relocating to areas of Fauquier County," said Weissberg President R. Lide Glenn. "We hope to transplant the success that we have had in Fairfax and Loudoun County shopping centers . . . to this area."

Baltimore County hired a private investigator to obtain the prices of condominiums at three developments, even though the prices were available from real estate agents, officials say.

Private Investigator Francis Alessi said he was hired by the People's Counsel Office to determine the selling price, density, sales rates and general appearance of two condominiums in the county and one in the city.

Deputy People's Counsel Peter Zimmerman said his office had not yet received a bill from the private eye.

The item became public during a hearing on a zoning-reclassification petition brought by seven property owners near the Bonnie View Golf Course who want the area zoned for higher density.

The property owners said they cannot develop the 32-acre tract without the zoning change because development costs are too high.