Two major Northern Virginia home building firms have started their own office buildings. Miller & Smith Inc. is building a three-story 21,000 square-foot building at Poplar Place and Elm Street in McLean. Edward R. Carr & Associates has started a three-story, 60,000-square-foot office building at 7535 Little River Turnpike in Annandale.

Richard G. Hines has been promoted to assistant vice president and general superintendent of residential construction of Kettler Brothers Inc. A native of Maryland, he has been with the firm for 20 years, most recently as coordinator of residential construction at Montgomery Village.

Connecticut General Life Insurance Co. has committed $16 million in permanent financing on a seven-story office building being built on Thomas Jefferson Street NW, south of M Street in Georgetown. James W. Rouse & Co. Inc. arranged the financing for Georgetown-Jefferson Associates, a limited partnership that is developing the 185,000-square-foot building.

The Montgomery County Board of Realtors will hold a seminar on financing of residential property on Sept. 12 at Indian Spring Country Club.

The Northern Virginia Board of Realtors recently named Donald R. Childress, a past president, as Realtor of 1979. Childress heads his own firm, Aries Real Estate Corp.

The National Association of Mutual Savings Banks will hold a mortgage conference at the Hyatt Regency Sept. 12-14.

Hallmark Development Co. Inc. has sold 26 lots in the first section of North River Forest, a two-acre-lot community near Annapolis.