A cashel is a type of early Irish stone fort, typically a roughly circular enclosure defined by a dry-stone wall, and this one contains within it the ghost of a rectangular room measuring roughly 2.2 metres north to south and 1.6 metres east to west. That is a modest space by any measure, somewhere between a large cupboard and a small garden shed in modern terms, and yet the deliberate placement of the structure against the enclosure wall suggests a practical logic: the cashel wall would have served as one ready-made side of the building, reducing the labour of construction considerably.

The structure was recorded by Thomas Johnson Westropp, an antiquarian who spent decades documenting the stone forts, ringforts, and early ecclesiastical remains of the west of Ireland at the turn of the twentieth century. His plan of Caherdoon, published in 1905, captured the layout of the enclosure and noted the building's position within it. What survives today is only the foundation course, the lowest layer of stones that once defined the walls, which is often all that remains of medieval structures built without mortar in the tradition of dry-stone construction. The internal dimensions Westropp recorded suggest a single-roomed dwelling or perhaps a storage or ancillary space associated with whoever occupied or used the cashel during the medieval period.