Archaeological monitoring during the restoration revealed that the rear portion of the house contained masonry belonging to an entirely separate phase of construction, one that predated the Georgian fabric surrounding it by perhaps a century or more.

The earlier structure, identified only at ground-floor level, measured approximately 12.8 metres long by 7.75 metres wide, and the archaeology suggests it may represent a fortified house, a type of defended domestic building common in Ireland during the 16th and 17th centuries, when political instability made a degree of fortification a practical consideration even for relatively modest gentry residences. The building had not been demolished and replaced; instead, it had been incorporated, its walls and footprint swallowed up when the more comfortable and fashionable 18th-century house was built around and over it. The later builders, in effect, used the older structure as a foundation and armature rather than clearing it away entirely.