In the late 1950s he became a partner in Treadwell and Wild. The 1958 Hazelcourt Flats in Claremont Grove is an example of their work from this period. Another of Treadwell's successful collaborations was the Willeston Galleries in Manners St with H. H. Geddes. He chaired a SANZ committee on drawing office standards and was actively involved revising the syllabus for architecture drafting courses for the Technicians Certification Authority of New Zealand. More recently he and his daughter Sarah recreated his mural in the Takapuna "Experimental House" by Group Construction for the 1950s show at Auckland City Art Gallery in 1992.