These structures, found across Ireland, functioned as a kind of rudimentary sauna: a fire would be lit inside, the embers raked out, and a person would crawl in to sweat out illness or physical complaint. The entrance to this one is deliberately punishing, a low rubble-built passage of limestone just 0.75 metres high and 1.7 metres long, entered by descending three stone steps from the north-west.

The chamber itself is modest almost to the point of invisibility. Sub-circular in plan and measuring roughly 0.9 metres by 0.75 metres, with a height of just over a metre, it is built primarily of limestone but switches to brick in its upper courses, a detail that hints at repair or adaptation at some point after the original construction. It sits on a slight rise of ground, the kind of position that would have offered a degree of drainage and perhaps a view over the lough. A ringfort lies approximately 180 metres to the north-west, a reminder that this landscape was settled and organised long before the plantation trees were planted around it. The proximity of both features on demesne land associated with Clonhugh House suggests a layering of use across many centuries, the sweathouse predating the formal estate that eventually enclosed it.