Trevor Old Mill

Trevor Old Mill is a tall, four-storey tower-like building with a single-storey lean-to extension on the southeast side. It is constructed of rubble stone with squared quoins and features segmental arches made of stone voussoirs for its windows and blocked openings. The building has a gabled slate roof with a central projecting gablet above the hoist on the northeast elevation, and a stone chimney stack at the northwest corner.

The main front, facing northeast, has a three-window range with a central doorway that includes a modern porch hood and six-pane double casement windows. The first floor features a central window flanked by blocked openings, while the second floor has two casement windows. The third floor is notable for its central cantilevered metal balcony supported by wooden brackets, a modern hoist door with an iron plaque embossed with '1848' above, and two additional casement windows. There are four iron tie-rod bosses on this elevation. The northwest and southeast elevations each have two windows, with the northwest elevation also displaying six iron tie-rod bosses. The southwest elevation features two randomly placed casement windows on the upper floors and an arched opening above the water-wheel axle at ground floor level.

The mill is equipped with a large diameter iron pitchback water-wheel that has twelve paired timber spokes and a wooden axle, along with an iron cogged external pit-wheel. The masonry wheel pit is recessed below ground level. An iron supply tank is supported on an iron half-trestle frame, and an iron supply pipe is held up by a timber frame at the water-wheel end, which is further supported by a freestanding rubble stone pier.

Inside, the mill has been modernised but still retains its timber main shaft and iron spur wheel at ground floor level. There is a dog-leg stone staircase leading down to a sub-rectangular basement that contains the main shaft and an iron cog-wheel.