This substantial defensive wall, which once enclosed the grounds of a tower house, stretches nearly 36 metres along what is now the boundary with the public road. Built with thick stone walls measuring up to 1.6 metres in depth and reaching heights of 3.4 metres, this imposing structure would have provided crucial protection for the castle's inhabitants and their livestock during troubled times.

The Civil Survey of 1654-6 offers a glimpse into Grallagh's past, describing the lands as having 'a good castle on them with a bawne & some few Tents. & Cabbins', with Thomas Butler of Kilconnel listed as the proprietor in 1640. The surviving eastern section of the bawn wall runs north to south, positioned strategically at distances of 11.4 metres from the tower house's eastern corner and 19.2 metres from its northern angle. Today, a modern concrete and stone wall separates the original tower house from a later farmhouse that sits to the southwest, whilst the historic bawn continues to define the landscape.

What makes this bawn particularly fascinating are its seven reconstructed gun loops, including two double loops, which pierce the wall at varying heights between 0.35 and 0.65 metres above ground level. These defensive features, with their flat-arched embrasures and wide internal splays, would have allowed defenders to cover multiple angles of approach whilst remaining protected behind the wall's substantial bulk. The internal embrasures vary considerably in width from 0.47 to 1.7 metres, with spacing between them ranging from 1.55 to 2.78 metres; evidence of practical defensive planning rather than rigid uniformity. Though the southernmost loop has been blocked up internally, the remaining openings still speak to the bawn's original purpose as a formidable defensive structure in the wet, undulating pastureland of South Tipperary.