It was badly damaged in 1762, reportedly by Whiteboys, the agrarian secret society active in mid-18th-century Ireland, and had still not been repaired when a visitor noted the fact in 1837. That the doorway survived at all is partly fortunate and partly the result of Board of Works intervention in 1881, when ivy was removed, gable stones were replaced, and the wall tops were pointed and concreted over. The building itself is a long, narrow rectangle, roughly 14.6 metres east to west by 5.5 metres north to south, with antae, the projecting pilaster-like extensions of the side walls beyond the gables, at all four corners. Two clearly different styles of masonry are visible in the fabric, a physical record of the building's gradual accumulation over several centuries.

The site has its origins in a monastery founded at Cluain Caoin by a saint known as Modhíomóg or Díomán, sometime in the 6th or 7th century, whose feast days were observed on the 26th of April and the 10th of December. The eastern two thirds of the present structure predates the 11th century, while the mid-12th century saw the addition of the Romanesque west doorway and an extension of the building to the west. In the 15th century, two ogee-headed windows were inserted, one a twin-light in the east gable and one a single light in the south wall, both cut from limestone rather than the sandstone used elsewhere, making them easy to identify. By 1615, the church was recorded as a chapel without a curate, its rectory lands held as mensal property by the Archbishop of Cashel, and in the same year it was noted as simply "down." The lands attached to it had by 1634 passed through a tangle of arrangements involving Abbey Owney and various members of the Bourke family, including Geoffrey fitz Ullick Bourke and his brother Edmond, who held half a ploughland called Maddybuoy, a name still preserved in the adjoining townland boundary to the east of the graveyard.

The church sits in flat pasture just north of the R506 Murroe road in County Limerick, in the northern quadrant of a graveyard that is hemmed in closely on its north and east sides, only four metres separating the church walls from the graveyard boundary on those two sides. A post-1700 cottage stands immediately to the west. The walls survive to their full height, which makes the building unusually legible as a ruin. The original round-headed window in the north wall near the west end, with its wide splay and rolled and filleted ornament on the inner jamb, is the one that most clearly belongs to the Romanesque phase. On the south side, opposite that window, there is a curiously tall, narrow opening cut from a single stone, with a square recess passing through the wall beneath its sill, the interior and exterior openings of identical dimensions owing to the sharply sloping sill and roof of the recess. It is not a feature that announces itself, but once noticed it is difficult to explain away.