Cefn-ydfa farmhouse and adjoining ruins.

Cefn-ydfa farmhouse is a stone-rendered building with a slate roof, dating from the 17th century. It stands two storeys tall and has four bays. The wide oak front door is positioned near the center and was originally part of the service hall from the mid-17th century. Both floors feature four small-paned oak casement windows, which are irregularly placed and date from the mid-20th century, all set under timber lintels. At the rear, there is a kitchen outshut that was added in the late 19th or 20th century. The house has gable stacks and a primary off-centre stack.

To the east, a former 18th-century house remains only as low walls, ending in a substantial partly-walled bay that shows an internal fireplace and openings. This earlier structure was originally two storeys with attics, five bays, and had five gabled dormers.

Inside the current house, there are large widely spaced chamfered cross beams without end stops. The fireplace in the secondary end bay has been altered and includes two side ovens from when it served as a kitchen, with a segmental rubble arch above. This bay was opened into the main central bay around 1974. The central bay features a stone axial fireplace, with the staircase located on its north side, and has chamfered ceiling beams and subsidiary joists with pyramid stops, though these are not currently visible. Originally, this room was subdivided to create an inner room, and it now has a recently introduced 19th-century Carrara marble fireplace.