Omni Construction Inc. has announced that major renovations have begun on the Washington Building, located at the corner of 15th Street and New York Avenue NW.

Originally constructed in 1927, the building will be modernized to accommodate current tenants. New limestone and granite will replace the existing facade at the first level, and an 11th floor will be added.

The penthouse will be raised and repositioned on the roof, and the existing limestone and cast-stone facade will be reinstalled.

The 11-story building has 215,000 square feet of leasable office space.

The Washington Building's lobby will be enlarged, and its original brass elevator doors and wood-paneled elevator lobbies restored to their original condition. Completion of the project is expected by next fall.

The building is owned by Washington Building Limited Partnership. Shepley, Coolidge, Bullfinch and Abott of Boston were its original architects, and Keyes, Condon, Florance Architects of Washington is coordinating its redesign.

Other recent developments in commercial realty in the Washington metropolitan area:

*Centennial Development Corp. has announced the signing of the following multi-year leases at Executive III, a six-story office building located off Sunrise Valley Drive in Reston: Merrill-Lynch Realty has leased 4,200 square feet; Reston Business Center Associates has leased 19,000 square feet, and Healthcare Communications Inc. has leased 6,200 square feet. The total value of the transactions is approximately $5.4 million.

*The Stanley Martin Cos. Inc. has announced that the State National Bank has leased a total of 11,500 square feet in the old W&J Sloane Building, which will be renamed the State National Bank Building. The bank will establish its corporate headquarters and main branch office at the recently renovated, 50,000-square-foot office building, which is located at 7220 Wisconsin Ave. in Bethesda.

*The Evans Co. has announced the purchase of the SAIC Building at Tysons Corner. Located at 1710 Goodridge Dr., the building is fully leased by Science Applications International Corp., a high-tech research and development firm based in La Jolla, Cailf.