Born in Quebec, Caddy studied at the Royal Military Academy, Woolwich, England in 1815 to 1816. The son of a Royal Artillery officer, he joined the same regiment in 1816, and served most of his life in the military, including the military in Canada in 1842-1844. He retire from the army with the rank of captain and remained in Canada to become the first city engineer in London, Ontario (1841-1851). He took up painting upon retirement from his job as an engineer. As a watercolour artist, he painted topographical landscapes and seascapes of Ontario and the Great Lake region, as well as flower studies, animals and sepia drawings.