Detached outbuildings to south of Melin-y-ddol

Melin-y-ddol is a mid to late 18th-century combined corn mill and miller's house with 19th-century alterations, set in an L-shaped plan with two ranges of similar length at right angles. The east-west range, which is slightly higher, represents the mill; the north-south range is the house. The building is 3 storeys tall.

The structure is constructed of random rubble masonry using local shale of poor quality, strengthened by timber noggings, many of which have been reused. The walls are limewashed except on the west side of the house, which is rendered. The building was constructed directly off bedrock and has slate roofs. Two red brick chimneys stand on the house, one near each end and one near the centre.

An additional parallel range to the west of the mill may originally have served as a cart shed. To the south of the house stands a detached structure incorporating an oven, which once butted against the south wall of the house.

The east elevation fronts the river, with the north end closest to the water power system. Both the house and mill portions were built as one integrated elevation. The mill's gable wall contains three windows, one on each storey, set under square-headed openings with wooden frames and glazing bars, though no glass survives. The house portion includes a tripartite wooden casement window on the second floor; one iron casement window on the first floor with 12 panes; and two iron casement windows on the ground floor, each with 16 panes.

The west side features two first-floor windows to the house, both iron casements with 12 and 16 panes respectively. A doorway to the house sits just north of centre, consisting of a wooden planked door under a square head, with a modern window to its south.

The south side of the mill contains a wooden casement window at first-floor level, with a 3-pane casement on the west side and a wooden shutter on the east side, beneath which are stable doors. The west end of the mill range has stable doors and a small high-level hatch. The attached additional structure to the west has a door at its east end and cart or garage doors at its west end, which cut through an earlier opening under a segmental brick arch. The west end is in poor condition, with cement rendering.

The south gable of the house has a timber dovecote attached under the eaves, and the scar of an adjoining structure's gable, which included the oven, remains visible.

The north elevation displays rough rubble masonry with extensive signs of repair and alteration. A wooden cam shaft for a former water wheel protrudes from a small round-headed opening with voussoirs at low level. No remains of the overshot waterwheel survive, though some ruined masonry and a cobbled stone floor represent the former wheel pit. A further round-headed opening above contains a wooden planked hatch. To the west is a further pair of round-headed openings, one below the other. At the west end of the north elevation stands a large concrete trough, approximately 10 metres west of the building and fed from the same race as the mill, together with a concrete cistern above.

The trough against the north elevation contains metal valve machinery at its east end, which passes into the mill, along with sections of large-diameter metal pipe. In front or east of the trough is a pelton wheel comprising three cast iron gears, each approximately 1 metre in diameter, with 6 spokes and numerous pairs of metal cups, evidence of later electricity generation.

Further outbuildings stand to the rear of the main building.

The interior was not accessible at the time of inspection in October 1995. The building is listed as a well-preserved mill and miller's house with evidence for both water power and later electricity generation systems.