Gwernhefin including Quadrangular Agricultural Complex adjoining to N

Gwernhefin is a late Georgian home farmhouse of considerable ambition, built of local slatestone rubble with roughcast to the principal elevations and slate roofs hipped to the house section. The squat brick chimneys have been rebuilt. The house stands two storeys tall with a five-bay front elevation, the left-hand bay recessed under the eaves. A two-storeyed gabled porch marks the centre of the original section, featuring plain bargeboards and stucco quoining. The porch door is an eight-panel, part-glazed example with a nine-pane sash window to the first floor above. To the left of the porch sits a 16-pane sash to the ground floor with a 12-pane sash above. To the right are two 9-pane sashes, with a smaller 12-pane sash to the left and a square 6-pane sash to the right at first-floor level. The right return, comprising two bays, is stuccoed and features a large 12-pane sash to the ground floor with its sill almost reaching ground level, an 8-pane twentieth-century French window to the right with a plain rectangular overlight, and 12-pane sashes to the upper floor.

The rear of the house is of rubble construction with asymmetrical openings and wide lintels, facing the enclosed yard. An off-centre entrance to the right has a boarded door and a three-pane rectangular overlight. A large window to the left and a smaller window to the right are set within primary openings. Four first-floor windows comprise three with two-part, multi-pane, iron-framed casements and one with a twentieth-century six-pane casement.

A quadrangular agricultural complex adjoins the house to the rear to the north. It comprises two-storey east and west ranges that adjoin the house at its north-east and north-west corners respectively, enclosing a large yard. A further range, continuing from the west range at right-angles, closes the yard at its northern end. Tall engaged gate piers mark the yard entrance between the termination of this northern range and the east range. The west range includes a further central arm that effectively divides the yard into a larger northern section and a smaller southern section. The ranges are of roughly-dressed slatestone, roughly coursed and galleted, with slated roofs partly finished with tiled ridges.

The eastern range features an extruded lean-to in the angle with the rear of the house and two cambered brick entrances with boarded doors to the left. Three ground-floor windows are present: that to the far right has two-pane sashes, while the remainder have fragmentary six-pane sashes with missing lower sections. Two loading bays serve the loft floor, with three further similar windows above. The north gable end has a boarded upper entrance with external stepped access featuring a modern rail. A slated lean-to to the east side incorporates two cart bays at the northern end.

The west range has an external stair leading to an upper entrance at the far left, at the junction with the rear of the house, with a segmental brick arch to the right giving access to the rear of the range and a small-pane cross-window above. The right-hand section, facing the yard, contains two entrances with boarded half-doors and a fragmentary sash window to the centre, with a ventilator to the left. Two large boarded loading bays serve the loft floor. The northern return of this range features a continuous lean-to with a corrugated asbestos roof facing the yard. Its north side, away from the yard, comprises a barn with a large, full-height central entrance and an adjoining section to the right with a rebuilt breeze-block upper section. Two ventilators serve the barn's east gable, with a boarded loading bay above.

The house contains plain interiors largely of the late nineteenth century. Panelled window reveals and six-panel pine doors serve the main rooms, some with overlights, and simply-moulded cornices are present throughout. The front right parlour contains a late nineteenth-century Rococo-style fireplace of pine with applied, gilded decoration and a bracketed mantelshelf. A narrow stair hall contains a straight-flight pine staircase with swept rail, stick balusters and a columnar newel, with pine-panelled understair.