Great Trewern barn, mainly stone built but having a timber-frame weather-boarded front facing onto the yard, stands on a downhill sited platform to the N. of the house. The ca.1800 barn is of 4-bays seemingly with some form of animal housing under a loft in the upper bay, although here the loft floor is now removed and the front wall partly ruinous; the S. gable-end wall which is partly built into the ground has no ventilation slits at the lower level although these occur in all the other stone walls.

The threshing bay has a large doorway in each side wall and a stone flagged floor. The outward opening double doors are well carpentered and could be locked on the inside by a draw-bar; in a upper panel of the E. door was a small shutter. On each side of the threshing floor the trusses have cill beams supported on high stone plinths, that on the upper S. side having a sheep-door under the cill at the W. end; there is a similar doorway under the cill of the S. truss, but at the E. end. The two trusses facing the threshing bay and that to the S. have raking struts above the tie-beam and a central post under. Curved down-braces support the main wall posts which also act as part of the door frame. All the timbers are clearly numbered with scribed assembly marks. While the N. gable-end wall is totally built in stone, that on the S. has has a timber-frame weather-boarded gable-end truss with its tie-beam seated on the stone wall. In the lower gable-end wall the are four tiers of ventilation slits; in both sections of the E. wall there are two tiers.

The roof over the barn is supported on trenched purlins, two to each side which overlap on principal rafters of each truss, and on a narrow upright ridge-beam. The rafters are notched onto the wall-plates. Some of the roof timbers are re-used from an earlier framed building.

[Additional:] Surveyed (level 3) in 1993. Farmhouse = NPRN 81251. (RFS/2002)