Measuring roughly three metres east to west, with a flat western edge running about four metres north to south, the spread consists of heat-shattered stones and soil darkened by charcoal, the characteristic signature of a burnt mound.

Burnt mounds are among the most frequently recorded prehistoric monument types in Ireland, yet they remain largely unfamiliar outside archaeological circles. They are thought to date primarily from the Bronze Age and are generally interpreted as the debris left by a process of repeatedly heating stones in fire and then plunging them into a water-filled trough, either for cooking, bathing, or some form of industrial preparation such as textile working. The stones, unable to withstand the repeated thermal shock, fracture and accumulate over time into the distinctive mound or spread visible today. The example at Ardagh came to notice not through formal excavation but through land clearance works, after which local information recorded what had been disturbed in the rough pasture. That kind of accidental discovery is not unusual for this monument type, many of which survive only partially, their full extent obscured by later agricultural activity or, as here, by clearance.