Trethill House

Trethill House is a house dating to circa 1830, with later 19th-century additions. It is constructed of rendered and lined rubble, with a hipped slate roof, deep eaves supported by brackets, and brick ridge stacks. The house has a double-depth plan, with a central entrance leading to an entrance hall and longitudinal corridor. To the rear are two principal rooms facing the garden, with a stair hall to the right of the entrance hall, and a lower, two-storey service wing to the right.

The front facade is symmetrical with three bays, the central bay broken forward beneath a hipped roof. It features double panelled doors with an overlight and sidelights, flanked by pilasters and a cornice. A 12-pane sash window sits above the entrance, within a moulded architrave with apron. Each bay to the right and left has a blind window at ground floor, also within a moulded architrave, and a 15-pane sash window at first floor, with an architrave resting on a cill band course. The two-storey service wing on the right has an end bay slightly broken forward, with blocked windows in a bow front. A single-storey bay at the front has a 12-pane sash window at ground floor, with a cornice on consoles, and two 20th-century sash windows at first floor.

The left side features a 12-pane sash window at ground and first floor to the right, and a canted bay to the left with margin-glazed sashes and a balcony above, likely dating from the later 19th century, with a 12-pane sash window above it. The rear of the house, which faces the garden, has a 12-pane sash window with sidelights and a cornice to the left and right, a central blind recess, all with architraves, while the first floor has three triple windows and a central single window, all with round heads and pilasters, and 8-pane sashes, set within a band course. The service wing on the left has an end bay broken forward with 12-pane sashes at ground floor and 6-pane sashes at first floor, and a ridge stack.

Inside, the principal rooms have moulded plaster cornices and marble fireplaces. An open-well staircase has paired turned balusters and a wreathed handrail. To the end right of the main range are rooms formerly used as a kitchen and a gun room.