At Ballinaclogh, groundwork exposed a burnt mound, one of the most common yet least understood monument types in the Irish archaeological record. These are roughly crescent-shaped accumulations of fire-cracked stone and charcoal-rich soil, found in their thousands across Ireland and Britain, typically beside water. Their purpose is still debated: cooking sites, saunas, industrial processing areas, or some combination of all three have all been proposed.

When archaeologist Goorik Dehaene excavated the site, the overall area investigated measured twenty metres by twenty metres. Within that, a burnt spread covering roughly 5.6 metres by 5.2 metres was uncovered alongside an oval pit measuring approximately five metres north to south, 1.5 metres wide, and 0.34 metres deep. The pit is the kind of feature that sits at the centre of the debate about burnt mounds: troughs like this, sometimes timber-lined, are thought to have been filled with water and heated using stones taken from a fire, the stones cracking and blackening in the process and eventually being discarded into the characteristic mound. Notably, the burnt spread continued westwards beyond the edge of the excavation, meaning the full extent of the deposit was never uncovered.