Lime kilns were once a familiar feature of the Irish rural landscape, used to burn limestone at high temperatures and produce quicklime for agricultural use, primarily to reduce soil acidity and improve pasture. Most have quietly crumbled into the hedgerows, and this one in Derrynacoulagh is no exception, though enough survives to read its original form with some clarity.

The kiln is horseshoe-shaped in plan, defined by a rubble wall with an earthen core standing roughly 1.2 metres tall and 1.2 metres thick. A break of about 1.3 metres on the south-east side marks where a recess once stood, the opening through which the burned lime would have been raked out once firing was complete, though the recess itself has long since gone. The stone-lined funnel at the centre, into which fuel and limestone were loaded from above, measures around 2 metres in diameter at the present top and tapers to approximately 1.3 metres at the base. The rear of the structure was cut directly into the hillslope, a common practical measure that allowed carts or barrows to reach the upper loading point without any great difficulty. Field walls survive to the north-west and north-east, and a scatter of large stones to the south may represent later collapse of the original fabric.