The castle sits just 20 metres from the stream below, a strategic position that would have offered both a water source and natural defence. Though the land belonged to Garret FitzGerald of Dromana in 1641, curiously no castle appears in records from that time; only a court gets a mention. By 1778, when cartographers Taylor and Skinner were mapping Ireland's roads, they marked it as already in ruins.

What remains today hints at what must have been an impressive fortified tower house. The southern wall has survived remarkably well, stretching nearly 14 metres in length and measuring 1.7 metres thick; substantial enough to withstand both siege and centuries of weather. Its base-batter, a defensive feature where the wall thickens towards the ground to deflect projectiles and prevent undermining, remains clearly visible. The main entrance, 1.3 metres wide, pierces the centre of this wall, whilst the western end once housed a newel staircase, now largely destroyed but still showing evidence of at least one window opening fitted with gun-loops for defence.

The castle originally rose at least four storeys high, with a stone vault running east to west over the first floor; a common feature in Irish tower houses that provided both structural strength and fire protection for the upper levels. These architectural details suggest Ballyheeny was built sometime in the late medieval or early modern period, typical of the fortified homes constructed by Anglo-Norman and Gaelic Irish families throughout Waterford during turbulent centuries when defence was paramount to survival.