1. Blaenavon Ironworks began production in 1789 and Stack Square was built between 1789-92 to house part of its workforce. It is a U-shaped block of which the south row is known as Engine Row, with a truck shop at the south-west corner. It was originally known as Shop Square but acquired its more recent name when a boiler stack was built in the middle of the square in 1853.

The 2 rows that make up Stack Square incorporate houses of different sizes and status. The east row comprises 5 single-fronted 2-storey houses in reflected pairs, of rubble stone and slate roof. Windows have brick segmental heads and restored 4-pane horned sash windows. At the left end is a lintelled doorway to a separate unit in the angle between the east and north rows, which has a now roofless 2-storey lean-to at the rear. The north row (similar to Engine Row) comprises 4 double-fronted houses of rubble stone and slate roof with later brick stacks. Openings in the lower storey have brick segmental heads replaced small-pane glazing, and all formerly had split boarded doors. Upper-storey windows are beneath the wall plate.

At the rear of the north row is a passage retaining original stone steps at the east end. It has arches across the passage providing buttressing to a retaining wall behind the house. 3 of the house have steps down to narrow back doors, while the north end house has only a small-pane window in the lower storey. The upper storey has a single replaced small-pane window in each house. The rear of the east row has a 2-light replaced casement in the upper storey of each house. The house at the north end has a blocked doorway inserted at intermediate level, while the remainder have segmental-headed 2-light lower storey windows and the house 2nd from the south has an inserted back door. The east row has 2-unit interiors. In the north row the first floors and wooden stairs have been removed, but original fireplaces are retained.

Additional information in Jeremy Lowe database of workers housing, ref 71, 82, 81
R Hayman, Hayman & Horton, 10/12/2002

2. Stack Square was photographed during Royal Commission aerial reconnaissance during filming of the BBC Wales documentary 'Coal House' on 10th October 2008, yielding aerial images showing the square set-dressed as it might have appeared during the Second World War.
T. Driver, RCAHMW, 3rd September 2009