Tregrug Barn, including attached stable and cart-shed

Tregrug Barn, including the attached stable and cart-shed, is a Grade II listed building constructed from local red sandstone rubble with Welsh slate roofs. The barn is a tall rectangular structure oriented north-south, parallel to the road, and features a lower cowshed attached to the north gable. A cart shed projects forward from the right side of the road elevation. The barn has two tall slit vents on either side of the opposing cart doors. It has a steeply pitched roof with a slight bellcast and a catslide roof over the cart shed. There is a tall slit vent on the right-hand gable, while the rear elevation mirrors the front but lacks the cart shed. A short slit vent is located on the left-hand gable above the cowshed roof. The cowshed includes three square-headed doors facing the road and has a shallower roof slope.

Inside, there is a timber tallet at the north end and an open hay-store at the south end, featuring splayed reveals for the vents. The barn has a paved threshing floor and a nine-bay roof that appears to include elements from the 15th or 16th century, such as an arch-braced collar beam with double collars, large principal rafters, purlins, and secondary rafters. Although only three of the arch-braced trusses remain, there are mortices indicating the presence of missing trusses, suggesting that the original design may have included a pitched barrel vault. This roof type is typically found in domestic halls and is believed to have been relocated from Llangybi Castle, which was demolished in the late 17th century.