"Preservation is better than restoration, restoration is better than reconstruction," architect Francis Don Lethbridge admonished Washingtonians for 30 years.

Saturday, it seemed as though everyone who had ever saved an old building, or wanted to, gathered to honor him in the rose-filled garden of the Columbia Historical Society's Christian Heurich Mansion.

Lethbridge was the first recipient of the society's Renchard Prize, honoring Washington preservationists Stellita and George Renchard, who both died in an automobile accident in January 1982. The Renchards' daughter, Roberta Renchard Freer, and sons Randolph and Ronald Renchard looked on while James Goode, award chairman, listed Lethbridge's good works.

Lethbridge organized the first Joint Committee on Landmarks of the National Capital in 1964, served as its chairman for 11 years and as a member until 1979, and compiled the first list of Washington landmarks. He is co-author of the "Guide to the Architecture of Washington." And he has been architect for the restoration of many historic structures, including four he has owned.

Goode suggested Lethbridge apply the $500 prize money toward restoring Mary and Don Lethbridge's 120-year-old house on Capitol Hill. "There are always cost overruns," said Goode.

Not all the conversation was congratulatory. Charles Atherton, secretary of the city's Fine Arts Commission, and Charles Robinson, president of the Dupont Circle Conservancy, worried about the Joint Landmarks Committee losing its place as guardian angel of Washington's great old buildings.

Recently, the National Park Service suspended the D.C. Office of Historic Preservation because of long- standing budgetary and staffing problems. In response, Mayor Marion Barry has nominated members (who must be confirmed by the City Council) to a new Historic Preservation Review Board, which is to assume most of the workload of the Landmarks Committee. Some observers were concerned that the board is more committed to development than preservation.

"We'll just have to keep an eye on them," said Lethbridge. "In the long haul, I'm optimistic that the District can't ignore the need for preservation. But I think the problem now is that buildings are preserved only to be slowly destroyed--such as Union Station. Seeing a building isn't demolished is only the beginning. But we came a long way in the '60s and '70s."

Lethbridge said that before the Landmark Committee, most people thought historic buildings had to have a federal front or classic revival pillars to be worth saving. "We rediscovered and gave landmark status to many fascinating later buildings such as the Old Executive Office Building, the Patent Office (now the Janus-faced National Portrait Gallery and the National Museum of American Art) and Washington's original city hall.

Lethbridge has been called "the dean of the Washington post-post-graduate school of architecture" because principals in 14 local architectural firms had their first jobs with his former firm, which designed the Holmes Run and Pine Springs communities in Fairfax in 1952; Carderock Springs, Md. in 1966; and Tiber Island-Carrollsburg Square, in Southwest Washington, in 1966.

Lethbridge now has his own firm and is currently working on two American consulates in Italy and the American embassy in Peru, as well as several houses. Recently he designed the Hammer Auditorium in the Corcoran Gallery of Art, and converted the old Pan American Union residence into the Museum of Modern Art of Latin America.

The 1880 Christian Heurich Mansion is being restored, as Jan Evans, a descendant of its first owner, pointed out Saturday. Perry Fisher, society director, said that for three days before the party Douglas Sprunt and other members of the New Scotland Garden Club carted out boards, pipes and debris to clean up the Victorian garden. The garden showed its appreciation by blooming lavishly for the party.