Thomas Dadford probably originated from Stewponey or Stourton, Staffordshire, near Stourbridge.
He started as one of James Brindley's many pupil-assistants, in which capacity he worked on the Staffordshire and Worcestershire Canal and the Birmingham Canal Navigations.
He worked on many canal projects, including the Neath and the Aberdare, in many of which he was also a shareholder.
Until 1794, with his son and Thomas Sheasby, he was engineer and contractor on the Glamorganshire Canal, until they had a row with the company and were arrested for alleged overpayments.
His last canal was the Montgomeryshire, where he succeeded his son John as engineer in July 1797.