Seibert was born in
Seattle, Washington on September 27, 1927, to Lt. Commander Edward C. and Elizabeth Seibert. His naval officer father was a civil engineer, and designed naval bases in the years prior to
World War II. The family was stationed in Hawaii during Seibert's adolescence. His parents were artists and intellectuals. He was home-schooled and was raised speaking Chaucerian English. In 1942, when his father retired from the service, the family moved to Sarasota, Florida. One of the interests that Seibert inherited from his father was sailing. They shared their interest in sailing together, and Seibert followed his father into the U.S. Navy during and shortly after World War II. Post-war, he attended
Stanford University to study art, but transferred to the
University of Florida to study architecture. As a new graduate, Seibert apprenticed in the office of architect
Paul Rudolph in Sarasota. There, he was exposed to Rudolph's design philosophy and architectural approach. Seibert once recalled Rudolph jotting a harsh remark on one of his early drawings. Seibert acknowledged that while such criticism was painful, he became a far better architect because of it. He and Rudolph ultimately became close friends. One of Seibert's first architectural projects was for
Philip Hanson Hiss III, a Sarasota real estate developer (Hiss Studio, designed in 1953). It was one of the first homes in Florida designed to accommodate air conditioning. Seibert's house, located on an inlet of
Siesta Key, was a small-scale crucible for his future designs, featuring many of the same elements. Both the Seibert House and Hiss Studio were recognized by the
American Institute of Architects as examples of extraordinary design, earning the 25 year
AIA Test of Time Award. In 1955, Seibert opened his own architecture firm, Seibert Architects. There he met some of his 'Sarasota School' peers, such as
Gene Leedy and
Victor Lundy. Their shared vision of 'clarity of concept (geometry)' and 'honest use of materials' helped define the modern movement known as the
Sarasota School of Architecture. Over the next forty years, Seibert designed hundreds of structures, both residential and commercial, along Sarasota's gulf coast. His work with Arvida Development Corporation on
Longboat Key resulted in the construction of buildings such as Far Horizons, Avenue of the Flowers, Beachplace Condominiums, Bayport Beach and Tennis Club, Inn on the Beach, and Sunset Place. At one point, Longboat Key city officials were certain that Seibert was involved in eighty percent of the development of the island. Other local work includes the Bay Plaza Condominium and additions to the
Field Club in Sarasota, Craig Residence, Mitchell House, Godfrey House, Dickerson Residence, 339-361 St. Armands Circle (Shopping District), Siesta Key Beach Pavilion, as well as the Siesta Key home of author
John D. MacDonald. Examples of his coastal work also extend beyond Florida to Georgia (Skidaway Island), South Carolina (Seabrook Island), Hawaii, the Caribbean, and Australia (Lilian Bosch Residence). ==Notable career achievements==