Tyddyn Iolyn Isaf is a small 2-storeyed house of the mid 18th century, built of local rubble stone, mostly rough cast. The house was renovated in 1932, so most of the external features, such as doors, windows and chimney are modern. Some internal features, such as some beams and panelling appear to be original and date to the mid 18th century.
Source: RCAHMW Caernarvonshire Inventory, Volume II