A lime kiln was used to burn limestone at high temperatures, reducing it to quicklime that could then be spread on fields to correct soil acidity or mixed into mortar for building. The Ballynacorra example faces west, its arched recess measuring roughly two metres in each dimension, a space large enough to have demanded serious physical labour and sustained heat. The funnel at the top, through which crushed limestone would have been loaded, is now infilled, and the recess arch that once opened to receive fuel and direct the draw has been filled with masonry, the wooden lintel that originally carried it long gone.

What survives tells you a good deal about how the kiln was operated. The stoking-hole, still evident at the base of the recess, is where workers fed fuel, typically coal or wood, to keep the fire burning hot enough to calcine the stone above. Slabs at the rear of the recess helped retain heat and direct it upward through the charge. A ramp on the south side allowed carts or barrows to reach the top of the structure so that raw limestone could be tipped directly into the funnel from above. The whole thing was built against the quarry rockface rather than freestanding, using the natural geology as a retaining wall. A stone wall now encloses the top of the kiln, though whether this was original or added later the remaining evidence does not say. Kilns of this type were common features of agricultural and industrial landscapes across Ireland from the eighteenth century onward, but relatively few survive intact enough to read in detail.