Among them stands a small rectangular building that rewards closer attention precisely because it is so easy to walk past. Measuring just 11.2 metres north to south and 3.75 metres east to west, it is modest even by the spare standards of early Irish monasticism, yet its fabric and layout carry a quiet coherence.

The building is constructed of mortared limestone masonry and retains the remains of opposing doorways at the southern end of its east and west walls, an arrangement that would have allowed passage through the structure and hints at a considered relationship with whatever activity or movement the surrounding complex demanded. Flanking the doorway in the east wall are two simple rectangular windows, and niches survive in both the west and north walls; these small recessed cavities in the stonework were likely used to hold lamps, vessels, or devotional objects. The building is recorded as closely resembling another structure in the same complex, referred to as Building A, a similarity noted by the archaeologist John Waddell in 1973, suggesting the two were perhaps conceived as part of a coherent phase of construction. The complex as a whole grew up around the cult of Saint Brecan, and Teampall Bhreacáin, or Temple Brecan, sits only about two metres to the south-east of this building, close enough that the two structures would have operated in clear proximity to one another within the wider monastic enclosure.