Corn barn at Trefarthen (S side of yard)

The corn barn at Trefarthen, located on the south side of the yard, is a five-bay structure dating from the 19th century. It features wide opposed doors at the center and is constructed with rubble walls that include two tiers of slit vents on the lateral walls, with seven vents on either side of the doors. The gable walls have three levels of slit vents, although some are partly blocked. The barn has a pitched slate roof with slate slab copings and a tapered finial with a weather-vane at the eastern end.

The central tall doors are set within a stone voussoir basket arch, and there is a pitching door above the door on the north side, along with a blocked door on the eastern gable. Inside, the roof is supported by four queen-post trusses. There is a beam intended to support a loft that formerly ran on either side of the door, but only one remains, marked with '1833' painted on it. The vents are fitted with small timber struts that once held wire bars. The area of the threshing floor between the doors is paved with stone slabs.