Tregonning Mill

Tregonning Mill is a miller's house, mill, and associated outbuildings dating from the early to mid-19th century. The construction uses granite rubble walls with granite dressings. The mill and outbuildings are roofed with gilled scantle slate, with gable ends, while the houses have replacement asbestos slate roofs. Brick chimneys rise from the gable ends and over the party wall of the houses, with one chimney extending above the mill's taller gable.

The building layout is a double-depth plan for the houses, and the mill is of the same depth, appearing integral to the house on its right. The outbuildings on the left are shallower. The mill and part of the adjoining house are likely the oldest sections, with the house plan subsequently deepened, followed by the addition of a house at the right-hand end and single-story outbuildings on the left. The mill was probably heightened when the first house was remodeled. Both houses feature two rooms at the front, flanking a central cross passage, with stairs and service rooms at the rear. A breast shot wheel and original machinery remain.

On the south-east front, the mill has a two-window facade with a central doorway and a loading doorway above. Originally symmetrical, the left-hand window opening was enlarged in the 19th century to create a tall doorway. Original divided ledge doors and windows survive, with a possible original 12-pane 2-light casement window on the first floor. Cast-iron ogee guttering runs under the eaves. A gabled dormer, clad in corrugated iron and featuring a wooden hoisting boom formerly used to lift sacks of grain to hoppers in the attic floor, is also present. The houses exhibit similar symmetrical three-window fronts with central doorways. One right-hand house has a blocked window above its doorway and contains an old ledged door and late 19th-century horned sash windows. The other house has similar 20th-century windows. The outbuildings, likely originally stables and waggon sheds, have irregularly placed window and doorway openings, with some late 19th-century windows and doors. The mill wheel has an iron hub, segments, wooden spokes, and buckets.

The mill interior, the only area inspected, contains 19th-century floors, roof structure, and machinery, including two pairs of stones on the first floor. The attic floor features hoppers on either side of a central working floor. The mill was in operation until recently and retains well-preserved machinery.