Dyfi Furnace is a fine example of a mid-18th century charcoal iron-furnace. The restored site is a hybrid; the flue is from its early days as an early eighteenth century iron furnace, and the thirty foot (9.14 m) diameter overshot waterwheel is from its later use as a sawmill. It is thought that it was a fulling mill at one time.
The original wheel which drove the bellows was enclosed in a small building and the site of the casting house would have been an open structure. There is an eighteenth century charcoal barn nearby at Grid Reference SN 6849 9510.
Pig-iron produced by the furnace would have been transported to the Midlands with a small amount used by local forges. The blast furnace went out of use in 1810.
During excavation work in the 1980's, evidence was found pointing to the possibility that the furnace was built on the site of a 17th century silver and lead works. It is thought that the Royal Mint in Aberystwyth Castle at the time, was secretly switched to the Furnace site during the Civil War of 1642-48.