The six-story L.F. Jennings Building at 4103 Chain Bridge Rd., Fairfax, has been leased by Zalco Realty Inc., a leasing firm.

Greenhorne & O'Mara, an engineering, architectural and planning firm based in Riverdale, has relocated its Northern Virginia branch to the Fairfax Mall at 10710 Lee Hwy.

Walker & Dunlop, a mortgage banking and realtor firm, has arranged a construction and permanent loan of $3.3 million for Heritage Hall, a one-story, 120-bed brick nursing home in Leesburg.

Ground has been broken in Salisbury, Md., for the second phase of that Eastern Shore city's first mid-rise condominium apartment, Canal Woods, on Tony Tank Lake. Fifty-two apartments are occupied now and 28 will be built.

Holland & Lyons, a Washington real estate and development firm, has opened an office at 2129 P St. NW.

Washington Homes Inc. is the builder of the first group of 55 houses to be started in Carrolltowne, a planned unit development in southern Carroll County, Md. Five models, priced from the $50,000 range, are open. The 190-acre site on Route 26 is east of Eldersburg.

The National Home Improvement Council has opened an office in the National Press Club Building, where Bruce Harrison is the manager. The Council, which is a trade association for home improvement contractors, has its main office in New York City.