He was born in Kristiania as a son of customs treasurer Thorolf Sommerfeldt (1849–1909) and Thrine Karine Sommerfelt (1856–1900).
In 1912 he married Sigrid Grøner, a daughter of district stipendiary magistrate J. C.
[1] He finished his secondary education in 1905, and graduated in engineering from Kristiania Technical School in 1909.
He was an engineer at Kværner Brug from 1909 to 1912, then in the insurance company Forsikringsaktieselskapet Norden.
He also chaired the Association of Norwegian Insurance Companies from 1941 to 1952 and Den norske Brandtarifforening from 1936 to 1957.