Most road users would not notice the distinction, but the bridge is effectively two structures fused together across several centuries, its various phases of construction still readable in the stonework if you know where to look.

The oldest surviving portion dates, on stylistic grounds, to the 13th century. The comparison is with Buttevant Bridge, a few miles to the south-west, where researchers O'Keeffe and Simington identified the same type of pointed segmental arch in 1991. Voussoirs, the wedge-shaped stones that form an arch, are cut rough and long in the medieval sections, a contrast to the dressed stonework added later. The bridge was already old enough to appear on the Down Survey barony map of 1655 to 1656, the mid-17th-century mapping project that recorded landholding across Ireland following the Cromwellian settlement. By the early 19th century, the structure had been substantially widened on its downstream southern side by around four metres, with new segmental arches and more carefully finished stonework. At the eastern end, two further arches were inserted at the same time to span the millrace of an adjacent corn mill, the larger of them fed by a weir built diagonally across the river upstream. A coursed ashlar parapet runs the full length of the bridge, its overhanging limestone coping tied together with iron bars. The original width of the medieval bridge was 3.5 metres; the piers between arches vary from two to more than three metres thick. One arch on the eastern side was replaced entirely with a flat modern arch in 1990, making the bridge a layered record of repair and adaptation rather than a single unified design.