Trefach Mill

Trefach Mill is a building constructed from rubble stone with a slate roof, featuring a square plan and a roof that is hipped at the northeast angle. The front of the mill is a single storey, while the rear drops steeply, revealing a basement ground floor and a loft. The west front has an elliptical arched cart entry on the right, which is framed by cut stone voussoirs. To the left of the roof hip and on the north side, there is a door and a window above.

The east front, facing the stream, has a gable on the right with a loft window in the center. To the left, there is a large elliptical arched doorway with a timber sill, leading down to an arched basement doorway that accesses the wheelpit, which houses the hub of an iron overshot wheel. Adjacent to the gable is a long pent roof that extends to the mid-height of the adjoining elliptical-arched doorway. The wall is buttressed, with one opening to the left of the buttress.

On the south end, there is one opening for the basement and one window. The deeply sunk east side features a loft floor in the northeast gable, a five-bay collar-truss roof in the west range, and a three-bay roof in the gable. There are remnants of machinery present. The mill is currently in a derelict condition, but there were proposals for renovation for domestic use in 1992.