Student at the Bauhaus. He studied in the carpentry workshop between 1921 and 1925. Previously, Diekmann had studied architecture in Danzig and painting and drawing in Dresden, although he never finished either degree. From 1925-1930, he was head of the carpentry workshop at the Staatliche Bauhochschule Weimar and taught at the Kunstgewerbeschule Burg Biegichenstein in Halle from 1931 until he was fired by the Nazis in 1933. For the remainder of his life, Diekmann worked for various furniture companies, designing standardized wooden furniture and the occasional piece in tubular steel.