Many aspiring architects attending his drawing school in preparation for admission to the Kunstakademiets Arkitektskole.
He was born to Peter Christian Nielsen, a master carpenter, and his wife, Ane Kirstine née Sørensen.
From 1847 to 1856, he was a regular visitor to a private school operated by G.F. Hetsch; first as an apprentice, then as an assistant.
In 1861, he married Caroline Jakobine Sørensen (1836-1878), the daughter of a master turner.
In addition to teaching, he was a regular contributor of drawings to the Illustreret Tidende, and produced a series of technically precise watercolors, depicting structural features.