Trevillyn Farmhouse

Trevillyn Farmhouse is a granite farmhouse dating to the mid- to late 17th century, with significant alterations and additions made in the mid-19th century and later 20th-century changes. The original structure is built of granite rubble with large granite quoins, and has a slate roof with crested ridge tiles and gable ends. It features gable end stacks, one rendered on the left and another with a granite ashlar shaft and cornice on the right.

The original plan consisted of two rooms: a larger parlour to the left and a smaller hall/kitchen to the right, each heated by its own gable end stack. A stair tower was added to the rear right of the kitchen. In the mid-19th century, a straight stair was inserted along the rear outer wall of the upper end room to the left, and two further room wings were added to the rear, each with a single-room plan and gable ends. A single-storey scullery/wash-house addition, heated by a gable end stack, was built to the rear right.

The front elevation has two storeys and three windows. A gabled and glazed porch with a 4-panelled door is present on the ground floor; the former position of a door is visible in the stonework slightly left of centre. There are 3-light casement windows to the right and left, the left window featuring a chamfered granite lintel, and the right window with a plain lintel. Three gabled dormers are above, each containing a 6-pane sash window. The roof level was raised in the mid-19th century.

The left side has a mid- to late 19th-century lean-to addition of one storey with an attic, featuring a 20th-century French window and a 2-light casement above. The right side has an external stack with an oven at the base and a pitched roof. A single-light window is on the first floor to the left. The stair tower has a hipped roof and two 20th-century blockwork buttresses, with a narrow single light window at ground floor level.

The gabled rear wing attached to the kitchen has a 2-light casement window at ground floor and a 6-pane sash at first floor on the outer side. An attached single-storey outhouse to the right has a door and a 4-pane light on the left side, and a further single-storey rubble addition with a door in the front gable end and a corrugated asbestos roof. This addition forms a 2-span roof and incorporates a 2-light casement and a rendered 20th-century addition to the inner side. The wing to the rear of the parlour, also two storeys, has a 2-light casement window in the gable end at both ground and first floor. The two gable ends form a valley with a central 2-light casement at first floor.

Inside, the kitchen to the front right has a heavy flat chamfered granite lintel to the fireplace, with plain granite jambs. An oven is located to the rear left, and a wall recess is to the right, covered by a timber lintel. A rear wall features an internal window with a timber lintel, possibly originally a doorway to the stair tower. The partition wall between the kitchen and the cross passage has been removed. The parlour to the left has a small fireplace with chamfered granite lintel and jambs, with a smaller granite fireplace inserted within. The stair tower contains a cambered timber lintel set low, the original function of which is unclear.