James Davidson Hossack was born in Banff, Banffshire, Scotland on 16 September 1892. He trained as an architect in the Architectural Department of the Pretoria Works Department in Pretoria, South Africa and at the Atelier Gromort in Paris. He then moved to London, England where he worked in the offices of E. Guy Dawber (1861-1938) and Mèwes & Davis.
In the early 1920s Hossack was in partnership with Thomas Penberthy Bennett (1887-1980) in the architectural practice Bennett & Hossack. In the late 1930s he was associated with the London architectural practice A. Marshall Mackenzie, possibly as a partner,
Whilst a student in South Africa, he received several prizes for designs, awarded by Herbert Baker to students of the Transvaal Society of Architects.
Hossack was elected an Associate of the Royal Institute of British Architects (ARIBA) in 1920) and a Fellow of the Royal Institute of British Architects (FRIBA) in 1932.
He died in Otford, Kent on 21 February 1975