Cochwillan Hall was built not earlier than 1450. It is a stone, hall-type house, with 2 moulded hammer-beam roof-trusses above a central hall, and 2 timber-framed partitions, against the 2 storey portion at each end.
The house was probably built by William ap Gruffydd (H. VII-Sheriff of Caernarvonshire), and was the residence of John Williams, 1582-1650, Archbishop of York.