The outer entrance features a round-headed arch, 2.48 metres wide, built with carefully cut limestone voussoirs, though the lower jambs have been lost to time. Evidence of the gatehouse’s defensive past remains visible in the covered portcullis slot and the large hanging eyes on both the north and south inner sides, which once supported a double door secured with a drawbar. While the outer wall extends northward from this gate, the southern section has unfortunately collapsed over the centuries.

The gatehouse itself, measuring approximately 7.6 by 8.7 metres internally, showcases the evolution of medieval architecture through its various phases of construction and modification. Originally accessed through a round-headed arch on the western wall, the interior featured elegant rib vaulting with decorative elements including a capital adorned with nailhead patterns and floral motifs, whilst the northern springer rests upon a carved head that has worn with age. The building includes practical features such as wall cupboards and a window with intact jambs, sill, and evidence of glazing bars. The northern gable wall, despite extensive repair work at its centre, still stands at full height and features a large centrally placed window set within a segmental-headed embrasure, with an offset that once supported a first floor.

During the 15th century, significant alterations transformed the gatehouse’s layout and function. The original western entrance was blocked and replaced with a smaller doorway, whilst a pier was inserted beneath the central ribbed vault to support two arches; the southern arch became an inner gate whilst the northern one survives as a round-headed doorway leading to a narrow chamber with partition walls. The building’s well-cut quoins on the northwest and northeast angles demonstrate the quality of its construction, and intriguing details like the gargoyle carved as an ugly human head on the external northern wall add character to this medieval structure. A long rectangular building, measuring 23.5 metres north to south and 8.7 metres east to west, connects to the gatehouse’s southern wall, completing this fascinating architectural ensemble that tells the story of centuries of Irish monastic life.