What began as a thirteenth or fourteenth century hall-keep underwent a dramatic transformation in the fifteenth or sixteenth centuries, when it was converted into a tower house; a change that reflects the shifting defensive needs and architectural fashions of medieval Ireland. The Civil Survey of 1654-6 paints a vivid picture of the manor in its heyday, recording not just the old castle but also six thatched houses and fourteen cottages, along with the legal privileges of a manor court that belonged to John Cantwell of Kilkenny.

The castle’s architectural evolution can be read like a historical document carved in limestone. The original hall-keep was a long, rectangular structure measuring approximately 11 metres north to south and 15 metres east to west, built from roughly coursed limestone rubble with walls over a metre thick. Initially only two storeys high with wooden floors supported by large timbers, the building was later raised to four storeys during its conversion to a tower house. This transformation involved significant alterations: earlier windows were modified, partial vaults were inserted over the ground floor in the southeast and southwest corners, and a large fireplace was added at ground level with its chimney stack projecting from the north wall, cutting across an earlier window.

Evidence of the castle’s defensive features remains visible throughout the structure. The south wall preserves traces of a crenellated parapet at wall-walk level, whilst an angle tower once rose above the parapet at the southwest corner, constructed using wicker centring techniques. Fourteenth century arcading with sloping stones at the east end of the north wall served to drain the roof, with a later series of drainage holes added when the roof was modified. A bawn wall, featuring a pronounced base-batter on its southern portion, extends from the northeast angle around the south side of the castle, providing an outer line of defence for this strategically positioned stronghold overlooking the waters of Lough Derg.