He was born in Kristiania as a son of wholesaler Oluf Christian Carl Sundt (1834–1891) and his wife Lydia Jeanette Dahl (1843–1891).
[1] After finishing Kristiania Commerce School, Sundt started a business career.
He was a board member of Greaker Cellulosefabrik, M. & H. Ingier, Oslo Smørfabrik, Aug. Pellerin Fils & Co., Oslo Sparebank, Den norske Naglefabrik,[1][5] and Det norske Myrselskap.
[9] From 1917 he lived at Gamle Madserud allé 37, in a mansion designed by Christian von Munthe af Morgenstierne and still known as "Sundtvillaen".
[10] In 1908 he established the architectural award Sundts premie for fremragende arkitektur.