He started his professional career working in the offices of Magnus Poulsson. He acted as a staff architect for Norsk Hydro in Rjukan, but returned to his own practice in Oslo in 1930. In the years 1935-36 he collaborated with the Czech architect Jan Reiner, who was a former assistant to Le Corbusier (1932–35). Bang's work included a number of residential buildings and institutional houses. Many consider Samfunnshuset i Oslo (the community building for the labor movement) to be his major work. He was a prominent advocate of Functionalism.