The walls, built mainly of uncoursed rubble limestone, now reach no higher than 2.5 metres at their tallest, and the east wall has vanished entirely. What remains is enough to read the plan: a nave roughly 16 metres long and a chancel of about 9 metres, both sharing the same width of nearly 7 metres. Two flat-arched, lintelled windows survive in the south wall, one in each section of the building, and the chancel example retains its red sandstone chamfered jambs, though surveyors suspect it may have been moved from its original position at some point. The crossing wall between nave and chancel still carries a pointed doorway with chamfered jambs, a small but legible piece of medieval stonework in an otherwise much-reduced shell.

The paper trail for this place is unusually detailed. Around 1240, Bishop Hubert of Limerick granted the advowson of Effyng, meaning the right to appoint its clergy, to G. de Prendergast. By 1287, Maurice de Rupefort had returned the church to Bishop Gerald, who promptly assigned it to fund two vicars at sixty shillings a year, with an obligation to say masses for de Rupefort and others. The arrangement placed the church within the patronage networks typical of Anglo-Norman ecclesiastical administration in Munster. Later records name a succession of individual clergy: John de Troye as prebendary in 1378, Richard Colman as clerk the same year, and John de Karlell as rector in 1388. By 1410 the church was formally recorded as dedicated to the Blessed Virgin Mary. T. J. Westropp, writing in 1904 and 1905, noted that the middle wall, the choir sides, and the south wall of the nave were still standing as late as 1840, suggesting that the most significant collapse happened in the later nineteenth century. The observation that the east end may have remained in use after the west end deteriorated points to a gradual rather than sudden abandonment.

The ruin sits in a sub-rectangular graveyard immediately to the west of the modern Catholic church in Effin village, County Limerick. The graveyard is still in use, so access is generally straightforward, though the church itself is described as very overgrown, and the fabric is fragile enough that picking through the interior requires care. The south wall, with its two windows, offers the clearest architectural detail. The crossing wall and its pointed doorway repay a closer look, as does the red sandstone in the chancel window jambs, a material that stands out against the prevailing limestone and raises its own quiet questions about where it came from and when it arrived.