Builth never became one of the showpiece Edwardian castles. Edward treated the destroyed predecessor as a blank slate and began work in May 1277, but construction stopped unfinished in August 1282 because money ran short. The likely reason for abandoning further work was that Llywelyn ap Gruffudd had been killed and Edward no longer felt the same need to pay for a stronger castle. Existing earthworks kept the cost below 1,700 pounds, making Builth comparatively cheap. The decision to stop followed the changing threat and available money, while the inherited earthworks had already limited the cost.
Chapter · 3:19-4:22
Edward I's cheap unfinished rebuild
Edward I's rebuild treats Builth as a blank slate, reuses the earthworks to limit cost, and remains unfinished when the wider Welsh threat changes.