Hi Eds
It appears Coflein believe this structure may not be as old as GAT previously supposed .... 'late medieval or earlier in date' (John Latham RCAHMW 13 November 2012).
Suggest a question mark may be required?
http://www.coflein.gov.uk/en/site/417976/details/LLYN+OGWEN%3A++MEDIEVAL+HOUSE/