The rath at Dirtane is a univallate ringfort, meaning it has a single enclosing bank and ditch rather than the multiple concentric rings found at more elaborate examples, and centuries of agricultural levelling have left it considerably reduced. What remains is a sub-circular raised area, roughly 41.5 metres north to south and 42 metres east to west, sitting within a gently sloping pastoral field. The enclosing fosse, a ditch dug to define and defend the perimeter, survives best along the northern and eastern arc, where it still measures around 2 metres wide and half a metre deep, though much of the rest has been worn almost flush with the surrounding land.

The interior itself is barely elevated above the ground outside, which speaks to the degree of disturbance the site has experienced over time. More intriguing is an oblong mound in the north-eastern sector, roughly 2.6 metres by 16 metres, which is likely the collapsed remains of a souterrain, an underground passage or chamber of the kind commonly associated with early medieval ringforts, used variously for storage, refuge, or ventilation of below-ground spaces. What survives above ground now as a grassy mound was recorded on the Ordnance Survey map of 1842 simply as a "cave", which is a useful reminder of how folk memory and cartographic shorthand can compress complex archaeology into a single word. Immediately to the east of the main enclosure is a separate sub-rectangular raised area, approximately 18 by 25 metres and rising to 1.4 metres in height, which is thought to be connected to the fort, possibly serving as an annexe or outwork of some kind, though its precise function is not firmly established.