The east gable still stands to something close to its original height, along with a substantial stretch of the south wall and a short stub of the north, but the west gable and most of the north wall were already down to their foundations when surveyors visited in 1840. The walls are built of small stones and measure roughly three feet thick, and the east window retains its single rectangular light set within splayed sides, the whole covered by a segmental arch. A similar window survives near the east end of the south wall. The masonry has been re-pointed in concrete at some point, which gives the remaining stonework a slightly incongruous tidiness against the graveyard grass around it.

The church takes its name from a dedication to Saint Fergus, and documentary records stretch back to at least 1201, when it appears as Killergussa. A series of medieval transactions recorded by the antiquary Thomas Johnson Westropp traces the church passing between various hands: it was granted to the Diocese of Limerick by one Adam Keyting in 1223, then assigned by Bishop Robert to John le Persoun in 1254, and returned to the See by John Brathnach in 1296. The name itself shifts across the centuries, appearing as Kilfeargussa in 1418, Kilfarasye in 1586, and Kilfergussagh in 1615, a small reminder of how fluidly place names were recorded before standardisation. The church lies within the parish of Shanid but is physically situated in the townland of Loghill, a short distance from Glin in west Limerick.

The site sits north of centre within Kilfergus graveyard, which remains in use, so access is straightforward. The ruins are modest in scale, roughly 12.8 metres long by 6.7 metres wide in their original footprint, and it does not take long to walk around them. The east window repays a close look: the splayed embrasure, where the window opening widens inward to admit more light, is a typical feature of early medieval Irish church architecture. By 1840 a doorway was still partially visible in the south wall, set about 2.7 metres from the west gable, though by that point only about 0.9 metres of the jambs remained, built, as the surveyors noted, of rough un-hammered stone.