He was a clerk for the district stipendiary magistrate until 1811. After some time in the Ministry of Finance, where he advanced to assistant secretary in 1817, he was transferred to law enforcement. He tried to become burgomaster, but instead served as Chief of Police of Christiania from 1823 to 1831.
In 1829, the so-called "Battle of the Square" took place.
Demonstrators were celebrating the Constitution of Norway, which had been outlawed by King Charles John of Sweden and Norway, and the police under Gjerdrum"s command intervented, causing a civic outrage. From 1831 to his death he was the stipendiary magistrate of Aker og Follo.
In 1845 he founded Nydalens Compagnie together with Adam Hiorth, Hans Gulbranson and Oluf North. Roll. He was a board member from 1845 to 1858.
Nydalens Compagnie developed into the largest textile company in Norway from the 1890s.