The join is legible in the stonework if you know what you are looking for, and a small stone plaque near the eastern end makes the later intervention explicit: "Corofin Bridge Drainage Commission 1848".

The older portion is thought to date from the seventeenth century and accounts for the ten westernmost arches, all round-headed and built from mortared limestone. One detail in the structure is particularly telling: the seventh arch from the west is noticeably larger than its neighbours, which suggests it once spanned the main channel of the River Clare before mid-nineteenth-century drainage works altered the river's course. On the upstream, northern side of these older arches, nine cutwaters project into the current, their triangular forms designed to divide the flow and reduce pressure on the piers. Above each cutwater, a small recess, called a refuge, is built into the parapet wall, allowing a person on foot to step clear of passing traffic. The southern face of the bridge, by contrast, is plain, without cutwaters or refuges, which is a clear sign that the structure was widened at some point, almost certainly as part of the same mid-nineteenth-century drainage scheme that extended the bridge eastward. That extension added further arches, with the twelfth and easternmost carrying the new drainage channel cut during the works. The first edition of the Ordnance Survey six-inch map records a bridge of twelve or thirteen arches at this location, and an earlier crossing point is thought to have existed a short distance downstream before this structure was built.