Engine Hall of former Llantrisant Colliery

The Engine Hall of the former Llantrisant Colliery is a large, two-storey building with a gabled roof, measuring 12 bays long and 2 bays wide. It is constructed of rendered brick sitting on a coursed sandstone rubble plinth, with red brick dressings. The building features lower projections at the center on both sides and has a slate roof adorned with a continuous glazed band on each side, terracotta ridge tiles, and five conical ventilators. The windows have segmental heads with deep, stepped surrounds and pronounced keystones, all made of red brick, reflecting the typical style of Powell Duffryn houses. The large windows on the main (upper) floor are metal framed, arranged in a 7 by 9 pane configuration, while the smaller ground floor windows are either 7 by 3 panes or 3 by 3 panes. An oculus on the northern gable has stressed voussoirs. Red brick pilasters separate each bay on the front, and there is a deep eaves cornice along with a string course at the main floor level. The engine hall was oriented towards the east side where the shafts were located, and the penultimate bays at either end had slots for winding cables. The eastern projection contains separate compartments for electrical gear and has a concrete cable support above it. Additionally, two blocked round-headed openings in the southern gable end previously provided access to the fan housing.

Inside, the main floor has high clearance and is exceptionally bright due to the large windows and continuous rooflights. There are two larger wells that open into the floor below, and an arcade leads to the rear projection. Pilasters run along the length of the hall, supporting a gantry for a 'Cargolift' travelling crane, which includes a driver’s cabin. The floor features red herringbone tiling and a terrazzo finish.