James Barnett was born in October 1827 in Almerclose, a village near Arbroath in Scotland. He was apprenticed to a builder in London in 1843 and took instruction in drawing and design under William Dyce. He studied Architecture for three years under Charles Richardson F.S.A.,F.R.I.B.A., School of Design, Somerset House, London. By 1854 he had worked for several years as a clerk of works for the Worshipful Company of Fishmongers and for a short time, in the same capacity, with Richard Suter, a London Architect. He was also employed as a foreman of works by T. F. Mathews, an architect and surveyor.
He was married on 22nd July 1854 to Amy Gosling, daughter of a builder.
He arrived in Sydney in December 1854.
He began business as a small builder in Glebe in 1855. He was employed under Edmund Blacket in setting out Randwick Asylum for Destitute Children (now Prince of Wales Hospital) and Sydney University.
He was appointed Clerk of Works in the Colonial Architects Office in August 1860. His design for the Sydney General Post Office was accepted in July 1862.
He was promoted to Acting Colonial Architect in November 1862.
He was appointed Colonial Architect in January 1865.
He resigned in June 1890.
He was elected Fellow of the Royal Institute of British Architects in January 1891.
He died in November 1904.
Buildings attributed to James Barnett include:-
- Balmain Court House
- Bathurst Court House
- Deniliquin Court House
- Goulburn Court House
- Lands Department Building, Bridge St., Sydney
- Newcastle Court House
- Orange Court House
- Sydney G.P.O.
- Yass Court House