Blaenavon Ironworks began production in 1789 with 3 furnaces. Two more furnaces were built c1810. The original partnership, led by the Hill family, sold the works in 1836 to the Blaenavon Iron and Coal Co. Initial investment at the site included the construction of a water balance lift for conveyance of pig iron from the site, but further investment did not occur until the 1850s. A new blast engine was built, and a new furnace was blown in during 1861. Investment was also made on a new site kown as Forgeside. By 1900 only one furnace remained in blast, but this was blown out in 1904. Thereafter the site was used by small-scale engineering companies until it became a guardianship monument in 1974.

The shed was built in the mid C20 when the site was used as engineering workshops. A brick shed with monopitched slate roof. The entrance is in a projection against the W end wall with boarded door. The N side has a 3-light casement window under a lintel, the W end wall a 6-pane horned sash window. The rear has an iron-barred 2-light casement.
R Hayman, Hayman & Horton, 6/1/2003