The farmbuildings to the S of Plas Tirion (NPRN 27773) include a dilapidated range that incorporates a distinctive cruck-truss with blades of boxed heart (whole tree) rather than halved timbers. The cruck and purlins are heavily smoke blackened and belonged to a medieval domestic building. This is the passage end truss of a downslope sited range which has been reconstructed beyond the lofted end bay, although some framing of uncertain date is incorporated in the stone walls. Whole-tree crucks are found among early pre-1400 crucks in England (but which have proved elusive in Wales). In the event, sampling showed that the trees were felled at the end of the fifteenth century, perhaps when large trees were not available. The cruck is associated with a later cross-beam in the passage which probably relates to an inserted floor.

Dendrochronology has therefore established an interesting and in some respects unexpectedly detailed chronology for the site:
1498 cruck-framed hall-house
1545/46 inserted beam at passage end of hall-house.
1565 Snowdonian house (= S Wing)
1626-8 Enlargement with the Snowdonian house becoming kitchen wing of the new range.