The building is substantial, running roughly eighteen metres north to south and five and a half metres east to west internally, with two fireplaces and a gable chimney surviving at its southern end. Details like these, a chimney still standing, hearths still legible in the stonework, are what allow a ruined structure to hint at domesticity rather than simply decay.

The building is described as a later addition relative to the tower house it accompanies, placed immediately to the north-north-west of the older structure. Tower houses were the dominant form of fortified residence across late medieval Ireland, typically built between the fourteenth and sixteenth centuries by Gaelic lords and Norman settlers alike. The residential range beside a tower house often served as expanded domestic quarters, providing the kind of ground-floor living space that a narrow tower could not easily offer. At Kilkeeran, the positioning close to the north end of the tower suggests the two structures functioned as a compound of sorts, the tower providing defence or status, the adjacent building providing everyday comfort. Lavelle's 1994 record remains the primary description of the structure.