What makes the surviving remains at Ballynakill quietly remarkable is that the two buildings are not really separate stories at all. They are the opening chapters of a single, layered structure that accumulated over roughly a century, each generation folding the previous one inside the next.

The oldest surviving fabric is sandstone rubble, randomly coursed, forming most of the south-east gable and a fragment of the south-west wall of a seventeenth-century house. The gable, some 5.5 metres long, retains its steep roof profile and a large chimney that once projected beyond the wall face. At some point in the late seventeenth or early eighteenth century, a second block was added to the south-west wall of this house, also featuring a pronounced projecting chimney. These two elements together formed what builders would have called a two-pile house. The eighteenth century brought the most ambitious intervention: a new house was constructed around and between these earlier structures, drawing the two-pile house and the old tower house into a single H-plan composition. The later building is ornamented with ovals and lozenges in the artisan-mannerist style, a decorative mode popular in Ireland during the late seventeenth and early eighteenth centuries that applied classical motifs in a somewhat free and vigorous manner. The south-east block of this final phase presents five bays and two storeys behind a blank parapet, with long rectangular windows; the central block rose to three storeys. The seventeenth-century gable was not demolished but absorbed, new floors inserted around it to create three storeys and an attic from what had been an older, simpler shell.

The site sits on a gradual west-facing slope in undulating pastureland, and the building as it now stands reflects that long process of accumulation rather than any single moment of construction. Reading the walls in sequence, from the rubble sandstone of the earliest gable to the mannered ornament of the Georgian facade, amounts to a compressed account of how an Irish landholding household rebuilt itself across several generations.