The D.C. Board of Elections and Ethics yesterday ordered a public referendum on the saving of historic Rhodes Tavern after a finding that more than the legally required number of city voters signed petitions asking that it be put on the ballot.

The issue probably will come before voters at the school board election scheduled for November, an elections board aide said.

The 182-year-old tavern at 15th and F streets NW, the oldest remaining commercial building in Washington and often described as the city's first but unofficial town hall, is on the site of the Metropolitan Square office and commercial project that already has been partly erected by the Oliver T. Carr Co.

Carr's firm won the legal right almost two years ago to tear down the tavern, but a group of preservationists has continued its campaign to save the three-story structure. The nonbinding election initiative would declare a municipal policy of saving the tavern and establish a seven-member board to seek ways to accomplish that goal.

The elections board approved the test of the initiative measure last July, permitting the Citizens Committee to Save Historic Rhodes Tavern to circulate voter petitions.

Yesterday, the three-member board certified that, based on a statistical sampling, the committee had collected 18,950 valid signatures of registered voters, 4,289 more than legally needed, and that the signatures were distributed geographically in the legally required way. The petition-gatherers had sumitted more than 25,000 "raw" signatures.

The petition-effort was made a success by signatures from Wards 1, 2, 3, 4, and 5, with Ward 6 "too close to call" and Wards 7 and 8 short.

Joseph N. Grano Jr., chairman of the citizens' committee, hailed the elections board's action and said it should help efforts that would be taken to block demolition, should Carr attempt it before the election.

The Carr firm has retained one of the city's leading law firms specializing in zoning and construction matters in its fight against the preservationist effort.

Philip Carr, senior vice president of the Carr Co., said he had no comment on yesterday's board action.