Barn at Upper Dyffryn

The barn at Upper Dyffryn is a large 19th-century structure featuring a lofted stable at the northwest end. It is built of rubble stone and topped with a corrugated metal roof. The southwest elevation faces the road and includes opposing doorways that lead to the threshing floor, which is located off-centre to the right. The barn doors are also made of corrugated metal. On either side of these doors, there are ventilation slits—one at ground level and one higher up.

The long wall of the barn on the left has a square doorway that leads to the pitching loft, with a boarded door secured by strap hinges. The northeast elevation faces into the farmyard and has vent slits on each side of the threshing floor, similar to those on the southwest elevation. To the right of the threshing floor, the stable features a slatted window with a segmental arched head.

The northwest gable includes a vent slit at the gable head and a ground floor stable doorway, which has a segmental arch made of stone voussoirs. This doorway is fitted with boarded half doors that have strap hinges. The southeast gable features an upper pitching loft doorway with a segmental arched head, while below, the wall has a single vent slit at both upper and ground levels.

The barn consists of five bays and is supported by collar trusses and two tiers of purlins.