The building's kitchens contain vaulted chambers that predate the elegant façade above them, hinting at a continuity of occupation that stretches back well beyond the eighteenth century. It is the kind of detail that gets overlooked when people are busy looking at the cathedral next door.

According to William Mason's 1819 account, the present deanery stands on the same ground as its medieval predecessor, meaning this plot has housed the cathedral's senior clergy for centuries. The Georgian building that replaced the earlier structure retained, or perhaps simply built around, two vaulted kitchen chambers that appear to be of an earlier date. A vault, in this context, is an arched ceiling of masonry, used in older buildings for structural strength and to reduce fire risk in working kitchens. The larger of the two chambers has a brick vault, while the smaller has a low barrel vault, meaning a simple continuous arch running the length of the space, constructed from stone and partially infilled with brick. That combination of materials suggests the chambers were adapted or repaired at different periods rather than built in a single phase.

The deanery is a private residence and not open to the public, so the vaulted kitchens are not something a visitor can simply walk in to see. What is accessible is the wider setting: the cathedral close around St. Patrick's retains much of its historic atmosphere, and the street pattern of the Liberties neighbourhood nearby preserves something of the medieval city's grain. Those interested in the archaeology of ecclesiastical Dublin will find the area worth exploring on foot, bearing in mind that the visible fabric of the deanery itself gives little outward sign of what lies below its ground floor.