Doldowlod was purchased by the engineer James Watt of Soho, Birmingham, in 1803. The present house, originally attached to an older farmhouse shown on the 1840 Tithe map, was built by his son James Watt junior (1769-1848) in 1843-5, modelled loosely on his Birmingham residence, Aston Hall. The architect was Robert Mylne. This relatively modest house comprised an entrance hall, dining room, drawing room and library, with service rooms contained within the attached farmhouse. The old house was demolished and an extension was built by James Watt Gibson-Watt (1831-91), who inherited Doldowlod in 1874. The extension, said also to be by Robert Mylne (although the Rhayader architect Stephen Williams is a possible alternative), closely matched the materials of the 1840s house, but in a more irregular, picturesque design. Changes were also made internally. The earlier entrance hall was converted to a study and the earlier dining room became the entrance hall. Drawing room and library were combined into a single room and a new library and dining room were contained within the extension, which also housed service rooms. The 1889 Ordnance Survey shows the service end of the house extending to a service wing left detached from the main house after some of the service rooms were taken down in the late 1940s.

Source: Cadw Listed Buildings. ALH 14/01/2013