That is more or less the full extent of what the formal record currently tells us. It has been noted, given a classification, and assigned an indeterminate date, which in archaeological terms is a category all of its own: not medieval, not post-medieval, simply unknown. The structure exists on the landscape in a state of bureaucratic suspension, recorded but not yet described.

Derryhillagh is a small rural townland in Mayo, a county whose interior is thick with the physical residue of successive waves of settlement, clearance, and abandonment. Houses of indeterminate date in this part of Ireland can range from pre-Famine stone cottages, built without mortar and roofed with sod or thatch, to earlier structures whose walls have collapsed so thoroughly that their original form is difficult to read. The label itself, "indeterminate date", suggests that whatever survives on the ground did not yield enough diagnostic features, such as a particular construction technique, a dateable artefact, or a clearly legible floor plan, to place it confidently in any recognised period. In a landscape shaped so profoundly by nineteenth-century eviction and emigration, that ambiguity is not unusual; countless structures were built, modified, abandoned, and partially robbed for stone across generations, leaving walls that resist easy classification.