After completing his training he returned to Eindhoven, and then on 24 September 1946, was part of an engineering battalion stationed in Indonesia to restore infrastructure in West Java.
[1] In 1950, he emigrated to Australia and was involved in the Snowy Mountains Scheme between 1950 and 1952, followed by work on Singapore plantations where he married a second time to June Sullivan and his second son was born.
He was prominent in the reconstruction of bridges in Indonesia after World War Two, innovative concrete structural designs in Australia, and his late life involvement in engineering heritage conservation.
[4] In 1971 he designed the concrete structure for the South Lawn car park at Melbourne University, described as ...saucer-shaped flowerpots on columns, interconnected to form arches.
[7] In 1982 Van der Molen was awarded a master's degree in civil engineering from the University of Melbourne and becoming senior lecturer in concrete design and technology and expert in timber structures.