It measures roughly 8.4 metres by 5.4 metres, subrectangular in plan, and is built in dry-stone construction, meaning the stones are laid without mortar, relying on their own weight and fit to hold together. A low internal wall, about 0.6 metres wide, divides the interior into two rooms. Whatever this building once housed, it was modest in scale and built to blend into the island's landscape rather than dominate it.

What makes the site particularly intriguing is what surrounds the structure. Immediately to the west sits a circular stone-lined depression, two metres wide and a metre deep, the kind of feature that could have served as a storage pit, a well, or something connected with small-scale processing or domestic use. To the northeast, a larger subrectangular area, about 13.4 metres by 10.8 metres, is enclosed by a dry-stone wall standing around 0.6 metres high. This enclosure, considerably bigger than the building itself, suggests the whole complex functioned as a small working compound of some kind, perhaps for keeping animals or managing resources from the island. The site was recorded in a 1994 archaeological survey of the Ballinrobe district, which covered the islands and shorelines of Lough Mask and Lough Carra. No firm date or function has been firmly established for the structure, and it remains one of those quietly unexplained corners of the Irish lake landscape.