Thomas Power was the son of Irish Catholic immigrants who moved to Newcastle from Bathurst when he was a boy. By the time he was eighteen he was a skilled carpenter. It was said that he worked first at ship construction. Later he was a leading designer and builder of both public structures and private homes, many of which are still standing. Miramichi Catholic churches which he is credited with erecting, and may also have designed in some cases, include the original St Mary's, Newcastle (1874), the Most Pure Heart of Mary, Barnaby River (1884), St Raphael's, Blackville (1892) (which was built from a design supplied by Patrick Troy), and St Samuel's, Douglastown (1901). Catholic churches which he is credited with both designing and building include St Thomas, Red Bank (1907); St James, Sevogle (1911), and St Joachim's, Eel Ground (1915). He also built Catholic churches at Tracadie and Bathurst, and although he was no longer active as a builder he "donated" the plans for St Stephen's Presbyterian Church at Sunny Corner (1930).
Newcastle buildings erected by Power include St Mary's Rectory (1884), the former St Mary's Convent and Academy (1895), and the former Newcastle Fire Hall (1898). He designed the Miramichi Hotel (1904), and although he did not build it, he did some of the finish work on it. He was not the contractor for the Harkins Academy annex (1909) or the County courthouse (1913), but he was engaged as the construction supervisor for both projects. He later built the Buie School (1918) and the Stothart Block (1918). Private residences erected by him included "one of the finest homes in Newcastle" for David J. Buckley (1916) and the "handsome" brick residence of G. Gilmour Stothart (1920).