The kiln uncovered during excavations at the castle site predates the castle itself, the mill that eventually wrecked it, and every defensive earthwork on the site. It is, in the precise language of the excavation report, the earliest feature present in the Southfield. What makes it quietly remarkable is not just its age but the detail in which it survived, and what that detail tells us about the people who built it before any of the more famous archaeology arrived on top of them.

Recorded by Breen in 2012, the kiln was found spread across Trenches 5 and 9 during excavations at Carrickmines Castle (DU026-005001-). It comprised a primary bowl feature, F868, with an attached flue extending up to 2.66 metres to the north-west, and a second bowl, F675, abutting it to the west. The main bowl was carefully made: a circular drystone wall with an internal diameter of 2.50 metres, its inner faces neatly dressed, with a trapezoidal gap left in the north-west for the flue. The wall stood between 0.55 and 0.60 metres tall when excavated, and the excavators believed this was close to its original height. Above the wall, deposits of heavily oxidised clay, burnt dark red and orange by sustained heat, suggested the bowl was once topped with a clay-covered frame, possibly a wickerwork dome, a construction method in which a woven organic frame is plastered with clay to resist combustion. Multiple layers of charcoal and collapsed daub inside the bowl hint that this superstructure may have partially fallen in and been repaired more than once during the kiln's working life. Eventually the kiln was deliberately backfilled, its bowl packed with silt and then a layer of large stones, and it was already abandoned by the time a horizontal mill was built nearby. That mill, when constructed, drove its headrace straight through the kiln's remains, robbing out sections of the wall and scattering rubble into the millrace. The cobbled floor beneath both bowls appears to have been an even earlier feature, reused as the kiln's base.

The site itself lies beneath what became the M50 motorway corridor in south County Dublin, and the excavation was carried out ahead of road construction. There is nothing to see at ground level today. The kiln exists now in the archive: in Breen's detailed stratigraphic report, in the measured drawings of bowl walls and flue cuts, and in the oxidised clay deposits that recorded, layer by layer, the slow life and deliberate ending of an early medieval structure that nobody had been looking for when the digging began.