Dowlais Works Blast Engine House

The Dowlais Works Blast Engine House is a very large industrial building constructed in red brick with yellow brick dressings, topped with a hipped roof behind a parapet. Although it appears to be two storeys with a high lower floor and an attic, it actually consists of a single open space inside. The side walls have nine bays, while the end walls have three bays, with the bays separated by piers featuring yellow brick quoins. The building stands on a rubble stone plinth and has a double yellow-brick string course beneath the upper windows, along with a similar triple course under the parapet.

The lower openings are long and arch-headed, framed by yellow brick rusticated surrounds and arches that include stone impost and key blocks. There are third-length windows in bays one, two, and nine, and a quarter-length window in bay five, which has a lintel below at mid-height over recessed walling with a yellow-brick arch and a fanlight above a narrower 20th-century door. Early photographs indicate that there was originally a tall arch under the window in bay five. Bay nine features a yellow-brick arched doorway that has been infilled with a small 20th-century door. The upper level has similar but shorter windows, and original metal glazing remains at this level, characterized by small panes and radiating bars.

On the rear northwest side, the upper windows match those at the front, but the lower bays feature blank long yellow-brick arched panels, each with two yellow-brick blank roundels above, all adorned with stone key and impost blocks. The central bay has roundels above a cast-iron portico supported by two columns on each side, topped with a corniced flat roof that resembles double-column responds. Two additional shorter columns are positioned on the flat roof, and there is a cambered-headed yellow-brick doorway within. The bays on either side of the center have only one roundel above the panel, which is asymmetrically set but mirrored on both sides.

The end elevations are similar to the main northwest front, while the southeast elevation is plain, featuring only blank yellow-brick framed panels at the upper level and two randomly placed roundel windows below. The building has not been inspected.