Washington Homes Inc. of Waldorf announced yesterday that a Washington area development and residential home builder has signaled its intent to make a formal proposal within the next 10 days to buy Washington Homes for more than $85.78 million, or $18.25 per share.

The expected offer from Preference Homes II Ltd. Partnership is the latest bid for the company and would top two offers made last month by other firms. The latest offer includes a provision for spinning off Washington Savings Bank, which is controlled by Washington Homes.

Sonny DeCesaris & Sons Development Group of Prince George's County has offered to buy Washington Homes for $84.6 million, or $18 a share. Scottish Heritage Trust PLC has offered $17 a share, or a total of $15.3 million, for 24 percent of Washington Homes.

Washington Homes is a major residential developer in this area and owns an 89 percent stake in Washington Savings Bank. The company earned $8.8 million on revenue of $89.5 million for the year ending July 31.

William J. Harnett, chairman of the board and chief executive officer, and Lawrence M. Breneman, president and chief operating officer, said the board of directors intends to evaluate the surprise offer if and when it is received. Washington Homes recently hired Thomson McKinnon Securities Inc. of New York as its investment banker to evaluate the other two bids. Washington Homes officials said yesterday that the company has requested additional information on the Sonny DeCesaris proposal.

Washington Homes has more than 4.7 million outstanding shares, as well as outstanding convertible subordinated debentures that could be converted into 1.25 million shares. Preference said its proposal to acquire the company for $18.25 per share in cash, would be extended to any of the company's outstanding convertible subordinated debentures that are converted into common stock.

Preference said its offer would include a proposal that Harnett and Breneman consider acquiring the shares of Washington Savings Bank owned by Washington Homes.