Egryn originated as a late medieval hall house (there is as yet no conclusive dating evidence but an earliest date of 1496 has been suggested), a substantial part of which survives as the core of the present structure. Recent dendrochronology has given felling dates of 1507-10 for the hall, 1592-1622 for the insertion of the upper floor. Its early plan comprised a hall with twin inner rooms and one or more outer rooms beyond the cross passage. In the late 16th or early 17th century, a lateral fire-place was added (replacing the open hearth), and an upper floor created over the hall. Later still, the inner end was altered, with the creation of a single room downstairs. An additional bay was also added at the east. The hall survives in its entirety, with its original roof structure intact (including a louvre truss - important evidence for the former existence of an open hearth). The aisle truss dividing hall from cross passage is intact, and the dais partition also survives to full height, with two doorways indicating the original arrangement of the lower end. The site of the outer rooms is now occupied by a mid 19th century range, but the line of the cross-passage is retained in the wide entrance/stair hall which runs the length of this range. It has been assumed that the original late medieval house was always stone-walled, and a late medieval stone doorway onto the cross passage tends to corroborate this. However the present walls show no obvious signs of disturbance associated with the insertion of windows of c.1600, and it is possible that much of the external stonework may date from this later remodelling.

The origins of the name 'abbey' are obscure, but the site has been proposed as that of a late 14th century hospital, founded for the poor and travellers on the Ardudwy coast.

The site is associated with a farm complex (which includes clamp/root store NPRN 308408 and dower house NPRN 407801), and all are now in the care of the National Trust. The 'Abbey' reference, formerly part of the long-standing place-name, is now not used by the National Trust because no evidence exists of any monastic associations.

RCAHMW, 24.06.2009.