That kind of architectural layering, a later domestic building grafted onto the shell or flank of a tower house, was not uncommon in Ireland during the 1600s, when the tower house form was becoming obsolete but the stone was too good to waste. What is unusual here is how completely the combined complex has vanished.

The house itself was a U-plan arrangement, a form characterised by a central block with two wings projecting forward to create a courtyard or forecourt between them. At Knockagh, that central block ran to three bays, with two-bay wings on either side, and the whole structure rose two storeys over a basement. The windows were flat-headed, as was the central doorway, and the roofline was punctuated by tall, rectangular chimney stacks. According to Mark Bence-Jones, writing in 1988, the building sat on the south-east-facing slope of a gentle rise in undulating countryside. That setting, a modest elevation in soft, rolling terrain, would have given the house a quietly commanding aspect over its surroundings without any great display of height or drama. At some point after that description was recorded, the structure was destroyed, leaving only the catalogue entry and the older tower house reference to mark that something considered worth documenting once stood here.