The only undeveloped site on the section of Connecticut Avenue between K Street and Dupont Circle will soon have a 118-foot office building with a shopping arcade, under a planned unit development approved by the D.C. Zoning Commission last week.

The white marble building, which will house the International Association of Machinists, will be built on what is now a parking lot and will be connected to the present machinists headquarters at Connecticut Avenue and N Street NW.

Plans for the building, by architect Vlastimill Koubek, also must be approved by the Joint Committee on Landmarks, since the site is in the Dupont Circle Historic District.

Without Zoning Commission approval, the developer could build only a 90-foot high building in the site. Under the planned unit development process, however, extra height may be allowed in exchange for "public amenities." In this case, that would include a shopping arcade, a pedestrian passageway through the building from Connecticut Avenue to 19th Street and an 8,000-square-foot park at the corner of 19th and N streets.

In other business last week, the Zoning Commission declined to take action, pending a study by its staff, on a request by the Adams-Morgan Advisory Neighborhood Commission for an emergency order barring the conversion of apartment buildings in mixed-use commercial zones to hotel and office uses.

According to the ANC, several apartment buildings in the 18th Street and Columbia Road NW area will be converted unless the commission acts quickly. The zoning commission is expected to consider the ANC request again at a special meeting Sept. 27.

Last month the Zoning Commission issued an emergency order barring the conversion of residential buildings in residential zones to hotel use.

The question of permanent, new zoning regulations for hotels was on the commission's agenda last week, but action was deferred until the November meeting.

The commission also deferred action on new rules for planned unit developments until its October meeting.