The D.C. Court of Appeals yesterday at least temporarily blocked the sale of the Tregaron estate in Northwest Washington, extending the history of family controversy surrounding the proposed sale.

In June, D.C. Superior Court judge Milton D. Lorman, weary of listening to squabbling heirs who couldn't decide how to sell the magnificant 20.7-acre estate on Macomb Street NW, ordered it sold for $4.6 million to the Washington International School and a developer.

Three heirs of Washington lawyer Joseph E. Davies who objected to the sale filed an appeal of Korman's order. Korman recently ruled that the sale could be halted pending the appeal if the objecting heirs posted a $5,566,000 bond, according to Scott Blake Harris, a lawyer of former Maryland Sen. Joseph D. Tydings, an heir who supported the sale.

Harris, who said an appeal might take a year and a half, said the objectors went to the appeals court yesterday to argue against the bond requirement. He said that he will argue early next week in favor of the bond, and that he expects a ruling on the issue soon thereafter. Nicholas Addams, the lawyer for the objecting heirs, could not be reached immediately.

Harris said the purpose of the bond requirement is to protect those supporting the sale from damages that might be suffered during the litigation of the appeal.

The proposed sale attracted attention both as a focus of family controversy among the Davies heirs and because the estate is one of the last major pieces of underveloped Washington land. The sale would allow the school to continue using the mansion on the property it now leases while the developer builds expensive homes on the surrounding terrain.