The small chapel, built by the Geoghegan family onto the southern wall of a medieval church, contains an inscription recording the death of Doctor Owen Geoghegan on 26th May 1778, aged 72, along with a request for mercy on the souls of his family interred alongside him. The slab has been incorporated directly into the east wall of the chapel interior, which gives the whole structure a layered, improvised quality, stone repurposed and repositioned across generations.

The Geoghegans were already associated with this land long before Owen's death. The Down Survey, a mid-seventeenth-century mapping project commissioned to document land ownership across Ireland, recorded the church on the lands of one Thomas Geoghegan, described in the characteristic language of the period as an 'Irish Papist' holding 271 acres in 'Killcrumriagh'. That survey, dating to between 1653 and 1659, shows the church as a rectangular building with what appears to be a residential structure or bell-tower at its eastern end. By 1837, when the first Ordnance Survey six-inch maps were produced, the church was depicted ivy-covered, with the Geoghegan mortuary chapel visible at the east end of the southern wall and a second mortuary chapel standing a few metres to the west. The site sits atop a low hillock in gently rolling countryside, with a post-1700 corn mill at Ballynabarna lying roughly 110 metres to the north-north-east and a mill race or stream about 70 metres to the east.

The fabric of the chapel itself is rough rubble construction, its walls standing around two metres high. A small window in the south wall, composed of two cut stone slabs with a round-headed top and measuring roughly 50 centimetres by 40 centimetres, appears to have been lifted from the medieval church and inserted secondhand into the chapel wall. A round-headed doorway in the east wall is damaged on the outside but retains a well-preserved stone arch internally. When examined in 1983 the entire chapel was badly overgrown with nettles and weeds, making close inspection difficult, and there is little reason to suppose conditions have improved greatly since.