He first worked with his father in the north of Britain on the Stour and the Trent, but later independently, contributing to a number of canal schemes, mainly in Monmouthshire and Glamorganshire but also in Montgomeryshire and Ellesmere, before dying at the age of 40.
[1] When he died, he left no will, but his wife obtained letters of administration in her favour; and his "goods, chattels and credits" amounted to £2,000.
In 1790 he assisted his father and brother John with a survey for the fledgling Neath Canal Company.
He was criticized by that company for his lack of attendance, but still managed to be the contractor for one section in 1795 and 1796, and to inspect and report on the final route with his father in 1797.
From January 1796 he was engineer for the Monmouthshire & Brecon Canal, devoting one quarter of his time to this task, and was still acting in this capacity when he died.
[1] During his brief working life Thomas Dadford Jr. managed to achieve a great deal.