Water Wheel House between slab mills at Felin Fawr Slate Works

The Water Wheel House at Felin Fawr Slate Works is a rectangular building, oriented roughly north-south, constructed of reddish brown brick in Flemish garden wall bond. It features a gable-ended slate roof, which has collapsed at the northern end and is mostly missing slates at the southern end. The eastern wall has two surviving full-height openings with slate lintels, while the south gable end contains a tall rectangular window, although the joinery is missing. The northern gable end has also collapsed.

Inside, the building retains an overshot wheel set low in a brick-lined wheelpit. The wheel has a cast-iron frame, with only the lower wooden paddles still intact. The interior also includes drivegear and related machinery, along with an ironwork header tank and panelled angle pilasters over the northern part of the wheelpit.