The remains belong to a rectangular hut, measuring roughly 8.2 metres north to south and 7 metres east to west, with walls about 0.6 metres thick. A central doorway opens on the east side, and one corner, the north-east, still retains its original internal stone facing. It is a small, quiet thing, but the precision of its construction and its proximity to a military tower make it worth a second thought.

Martello towers were built around the Irish coastline in the early nineteenth century, during the Napoleonic Wars, as a defensive measure against the threat of French invasion. Squat, circular, and built to a largely standardised design, they were garrisoned by small numbers of soldiers, and the hut at Ardagh is almost certainly connected to that military presence. A structure of this kind, positioned to the south-east of the tower on flat ground, would have served a practical purpose, perhaps as accommodation for additional personnel, a store, or a working space associated with the garrison. The survival of the internal facing on the north-east corner is a small but telling detail; it suggests the walls were finished to a reasonable standard, not merely piled up as a temporary shelter.