Blaenavon Ironworks began production in 1789 and Stack Square (nprn 20853) was built between 1789-92 to house part of its workforce. It is a U-shaped block of which the S row is known as Engine Row (nprn 36837), with a truck shop at the SW corner.

A 3-storey shop of rubble stone with slate roof and reduced stack to the L side wall above the roof line of Engine Row. The main entrance is in the single-window W gable end, which has replaced small-pane windows in brick segmental openings and a split boarded door to the R. The S side, which is only 2-storey because the ground is higher, has a segmental-headed boarded door to the L and 2 small fixed windows. In the upper storey are 3 blocked windows. Of a former parallel range to the S side, only low walls and a gable end on the E side remain standing. On the N side, behind Engine Row, are small-pane windows in each storey, under a segmental head in the lower storey.

R Hayman, Hayman & Horton, 6/1/2003