Construction has been started on a $17-million, eight-story office building at 2121 K St. NW. The Oliver T. Carr Co. is handling development, leasing and management of the building named for the late Washington businessman Thomas W. McGregor. Weihe, Block, Jeffries, Strassman & Dove designed the building to have 118,000 square feet of commercial space.McGregor Properties Inc. is the owner of the building, and the general contractor is the George Hyman Construction Co.

Danac Associates Inc. has named Lawrence C. Sween and Robert L. York Jr. to handle the leasing of the Rock-Wall II office building that is nearly completed on Rockville Pike opposite the White Flint Mall. Danac Investment Inc. developed the 185,000-square-foot building that is owned by Equitable Life Assurance Society.

ADD Inc., an architecture and interior design firm based in Cambridge, Mass., has opened a Washington office at 2000 L St. NW. Michael Hickok, a project architect with ADD since 1976, will head the new office.

Courthouse Plaza II, a low-rise commercial building complex in the City of Fairfax, is expected to be ready for occupancy next month. The 100,000 square feet of rental office space was designed along colonial lines by Bucher & Meyers. Leasing, which is being handled by Shannon & Luchs, is in the range of $10.50 to $13.50 a square foot.

Dennis and Gary Berman recently purchased a tract in the White Oak area of Silver Spring as a site for a White Oak Racquetball Club that will include 12 courts, a nursery, locker rooms and parking. Wolfgang Mueller of Snider Bros. handled the land transaction. Construction is expected to be completed this fall.