Sweathouses, known in Irish as tigh alluis, were a surprisingly widespread feature of the Irish countryside, particularly in Ulster and Connacht, and were used for therapeutic sweating long before the concept of the bathhouse reached rural communities through any formal channel. The person seeking relief from rheumatism or skin ailments would heat the interior with a turf fire, rake out the embers, and then crawl inside to sweat in the residual heat before plunging into a nearby stream or pool.

The Tullynafreave example is a compact, carefully built thing. Its drystone construction uses no mortar, relying instead on the careful placement of stone upon stone, and the beehive-style corbelling draws the walls inward as they rise until two flat slabs close the roof at a height of just 1.1 metres. The interior diameter is 1.3 metres, which gives a sense of how intimate the experience would have been. The entrance faces south-east and is lintelled, meaning a single horizontal stone spans the opening, which stands only 0.6 metres high and 0.4 metres wide. You would enter on your hands and knees. The structure is partly built into the hillside at its north-western side, which would have helped retain heat. Notably, it does not appear on either the 1836 or 1876 Ordnance Survey editions, suggesting it had already fallen out of regular use or recognition by the time those maps were made. Richardson noted it in 1939.