Plas Penmynydd is constructed of limestone rubble under a slate roof. The original house was built in 1576 although part of this section was probably partly destroyed during the seventeenth century rebuilding as few original features remain in this section. A sixteenth century stone corbel with a carved human head, used to support hall roof truss, may have originated from a different structure.

Plas Penmynydd was the home of Owain Tudur, who anglicised his name to Owen Tudor and married Queen Katherine after the death of her husband, King Henry V. Owain's grandson, after winning the Battle of Bosworth for the English throne in 1485, became King Henry VII and became the first of the Tudor monarchs.

J Hill, RCAHMW, 14 November 2003.

[Additional:] A substantial gentry house of Snowdonian type with a lateral chimney built in 1576 (datestone) and partly reconstructed in the mid-seventeenth century. Fully described with plan in RCAHMW, Anglesey Inventory (1937), pp. 130-1.

Tree-ring dating commissioned by North-West Wales tree-ring dating project in partnership with RCAHMW in 2010. Six timbers in the roof and one ground floor ceiling beam were sampled, all of which were thought to date to a known building phase of 1576. Matches were found between three timbers (two from the roof and the ceiling beam), all of which were felled in the same year, but none of the series were dated.

Full report available in NMRW. (NJR, 07/04/2011)