Sennhauser was born in Switzerland but raised in Italy where he studied for two years at the Royal Academy in Venice before immigrating to the United States in 1928. In New York he studied at the Cooper Union School from 1930 to 1933. He was a teacher at the Leonardo da Vinci Art School and Contemporary School of Art in New York before taking a job at the Solomon R. Guggenheim Foundation in 1943. It was around this time that his paintings began to lean towards abstraction and away from the more representational urban street scenes of his early career. After two years at the Guggenheim he left and began work in art restoration and became increasingly active in such organizations as American Abstract Artists and the Federation of Modern Painters and Sculptors. Like many of the Abstract Expressionist painters of his time Sennhauser eventually returned to more figurative works in the 1960's. These works were more fluid than the strong geometrical feel of his works from the late 1930's through 1950's.