William Arthur Purnell was born on 5 January 1878 at Geelong, Victoria, the second child and eldest son of eight children. He was called ‘Arthur’ so as not to be confused with either his father William Purnell Jnr or his grandfather William Purnell Snr. Purnell grew up and was educated in Geelong. He attended McManus Preparatory School, Flinders School (now Matthew Flinders Girls Secondary College), Geelong College, where he developed a keen interest in sport, Gordon College (now Deakin University), where he studied architecture, and the Geelong School of Arts, where he studied drawing.

Purnell’s father, William Purnell Jnr, was an architect/builder with Purnell & Sons, a prosperous Geelong building firm established in 1876 by Arthur’s grandfather William Purnell Snr. In 1895 Purnell joined Purnell & Sons as a draughtsman. After passing the prerequisite Geelong and Melbourne exams, Purnell passed the Victorian government exams in architecture, building construction and perspective drawing in 1896. He won prizes for his drawings at several local arts and crafts exhibitions, as well as the Paris Exposition. After studying under C.A. Heyward, a government architect, Purnell gained certificates for theory and practice in advanced trade classes from the Victorian Education Department.

Purnell married Jane Farrell in 1908. Her parents were pastoralists from Lake Monemia near Streatham, Victoria. The Purnells had one daughter, Joan. Arthur Purnell died on 29 June 1964 aged 86.