Cochwillan 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 central entrance doorway has moulded jambe and depressed arch. The Gothic mullioned windows are somewhat damaged, with one filled in. There is a wide projecting fireplace with double-ogee moulded beam above the opening. 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. Much exeptionally good work remains.

Reference in R.C.H.M. Volume I (474) and in Old Cottages of Snowdonia by Hughes and North.
(Source CADW listed buildings database)
J Hill 29.10.2003

Additional:
Plans, sections, and cutaway in 'Houses of the Welsh Countryside', figs 69-70.
Assessed but rejected for tree-ring dating 2011 as the accessible timber is relatively fast grown.
See the Centre for Advanced Welsh and Celtic Studies' on-line resource Guto'r Glyn.net poem 55 for Guto'r Glyn's poem in praise of Wiliam ap Gruffudd of Cochwillan. From the notes to Poem 55:
This is a poem of praise to Wiliam ap Gruffudd of Cochwillan in the parish of Llanllechid in Gwynedd which Guto composed when he was an old man. Wiliam's hospitality is thoroughly praised in the first 34 lines and Guto states his intention to stay in Wiliam's court for the rest of his life. It seems that the existing house at Cochwillan was built during the second half of the fifteenth century by Wiliam himself, although the poet Gwilym ap Sefnyn clearly states in a poem to Wiliam's grandfather, Rhobin ap Gruffudd, that there was a house at Cochwillan at the beginning of the century (see Williams 1997: 91). Smith (1975: 102) argues that Wiliam renovated or rebuilt the house sometime after 1485 when he was appointed sheriff of Caernarfonshire following the support he gave to Henry Tudor at Bosworth: `It is fair to surmise that Gruffydd [that is to say, Wiliam] built his great hall to support his newly exalted position in society, and he built it in the latest fashion for a great gentleman, with an outstanding hammer-beam roof, glazed windows and a side-chimney?. See RCAHM (Caernarvonshire) 134?6; Smith 1975: 100?2, 130?1, plates 26 and 27; Haslam et al. 2009: 518?20, plate 47.

RCAHMW produced an exhibition panel on houses described by Guto for use at the National Eisteddfod and other public events (2011-13), and Richard Suggett collaborated with the Canolfan's project team in the design of the Cochwillan 3-D animation, which represents a significant advance on previous computer-generated depictions of medieval houses in that it shows the building in a living cultural context with accurate reproductions of contemporary furniture. The animation was produced by the commercial graphic design company See3D, with interactive resources developed by Technoleg Taliesin providing text and translation of the poem recited and information on artefacts produced by members of the project team. It is available on YouTube as well as on the `Guto's Wales? site.

R.F. Suggett/RCAHMW/2013