A bawn is the defensive enclosure wall surrounding a tower house, and in this case the seventeenth-century structure was built directly against the external face of that wall, making the bawn itself one of the house's defining architectural neighbours. What survives today is poorly preserved, but enough remains to read the original intention: a simple two-storey rectangle, roughly nine metres north to south and just over four metres wide, with a projecting chimney stack on the north gable.

The construction details that survive are quietly revealing. The original fireplace was framed with a large wooden lintel, with cut-stone voussoirs, the wedge-shaped blocks that form an arch, arranged as a relieving arch above it to distribute the weight of the masonry overhead. The floors were carried on substantial east-west beams slotted into beam-holes in the walls, with smaller north-south beams laid across them, a straightforward but sturdy arrangement typical of domestic building of the period. Sometime in the eighteenth century, additions were made to the north, east, and west walls, and those alterations have since obscured much of the original ground plan. The attached five-bay house to the east, dating to the early or mid-eighteenth century, is also two storeys, with gable-ended chimneys and a plain flat-headed doorcase, representing a more formal domestic sensibility than the rougher seventeenth-century range beside it. Together the two structures chart roughly a century of gradual settlement around Lackeen tower house, each phase building on or against what came before.