Archaeological surveys conducted by Ua Cróinín and Breen in 2005 uncovered traces of what appears to be a bawn wall, positioned roughly 15 metres west of the main structure. These linear stone remnants represent part of the defensive perimeter that would have once enclosed the tower house grounds, providing an outer layer of protection for the inhabitants and their livestock.

What makes this site particularly intriguing is a feature spotted through satellite imagery. Digital Globe images from 2011 to 2013 reveal what archaeologists believe to be a rock-cut fosse; essentially a defensive ditch carved directly into the bedrock between the bawn wall and the tower house. This type of dual defence system was relatively sophisticated for its time, creating multiple obstacles for any would-be attackers attempting to reach the main tower.

The combination of tower house, bawn wall, and fosse at Derryowen offers a glimpse into how seriously medieval Irish families took their security. Rather than relying on a single fortified structure, they created layered defences that would have made any assault considerably more difficult. While much of the original construction has been lost to time, these archaeological traces help us understand how people lived, defended themselves, and adapted to the political uncertainties of medieval Ireland.