T-Shaped Range to rear of Pengwern Hall (including Vaulted Undercroft)

2-storeys. Comprises a short medieval C13/C14 cross range (containing the undercroft) linking the main house with its parallel agricultural range which is probably C17. It is conceivable that the medieval part was built by Lord Iorwerth of Pengwern when he was Seneschal to Prince Madog (ruler of northern Powys) in early C13; later alterations probably contemporary with the C17 building. The agricultural range is distinctive for the reused Gothic feature, presumably from Valle Crucis Abbey and probably inserted contemporary with the ca 1770 remodelling by Sir Roger Mostyn. Rubble construction with undulating slate roofs. Red brick chimney stack to the medieval part; some of the NW side of which is concealed by the kitchen range of the house. Brick stairs with stone treads rises to boarded door with chamfered freestone surround. The SE side overlooking the garden has 2-narrow splayed openings and a larger one (former doorway) with inserted brick buttress to right; staircase removed. Small casement window below to left. At right angles is the agricultural range; the garden facing front of which has freestone surrounds to all windows; that to 1st floor is sub-medieval with mullions removed. The gable end with stone parapet has had a C14 3-light window inserted over a smaller opening; cusped ogee lights and one mullion partly replaced in timber. One stone to right is intailled R C D. At the other side of the cross range there is a 2-bay rubble front with diamond shaped ventilators and brick cambered arches to stable doorways and window. The rear elevation has a cusped lancet window beside a 1st floor boarded door; further to NW is a 2-light sub-medieval window with mullion removed. Later brick openings below. Long barn range stepped down to NW. Stone gate piers at SE corner.

Within the cross range is the 9-bay barrel vaulted undercroft with pointed and chamfered stone ribs. Stone flagged floor and stop chamfered jambs to the doorway. Springers above indicate that the upper was once similarly vaulted; now with trenched purlin trusses. 6-bay roof to the other range, with overlapping purlins.