Ballyskeagh Bridge, Ballyskeagh Road, Lisburn, Co Antrim

Ballyskeagh Bridge is a twin-span masonry arch bridge carrying Ballyskeagh Road over the Lagan Navigation between Belfast and Lisburn. Built between 1760 and 1779 of Triassic sandstone, it was designed by canal engineer Thomas Omer as part of the government-appointed Corporation for promoting and carrying on an Inland Navigation in Ireland. Work on the navigation commenced in 1756 and opened in 1763.

The bridge is one of only two examples on the Belfast-Sprucefield section where the towpath runs under a road, though unlike Moore's Bridge at Lisburn, this one required the towrope to be unhooked so that the barge and horse could pass through their respective arches. Architecturally, it is among the most impressive canal-related bridges in Northern Ireland, remarkable for its scale, proportion and quality of workmanship. The canal cut and bridge represented the largest single items of civil engineering work on the entire navigation.

The structure comprises two semicircular arches of different sizes: the larger spanning the water channel, the smaller spanning the former towpath on the east bank, now a public footpath. The abutments and central pier are of dressed sandstone blocks brought to courses and embellished with vee-jointed cut stone quoins. As the pier rises from the bank, no cutwater was required, though towrope marks are visible on its quoins. Both arches have vee-jointed cut sandstone voussoirs stepped into the spandrels with raised keystones. The main arch over the water features three putlog holes at spring level. Its soffit has been reinforced with cast-in-situ concrete and is held at crown level by a tie bar. The soffit of the footpath arch has been gunited, replacing earlier brickwork. A string course runs around the abutments and pier at arch spring level. The spandrels are of squared rubble with a string course above. The parapets are of random sandstone rubble with some quarried basalt and Silurian shale, coped with concrete, though sandstone coping blocks possibly original survive at the west end of the north parapet. The carriageway comprises two lanes without a footpath; pedestrian traffic is carried on a modern single-span metal girder footbridge immediately to the north. A concrete steps flight runs up the south-east side, probably a modern rebuild of steps that enabled the lock keeper living in the adjacent lock house to access a lock north of the bridge.

Ballyskeagh Road was one of the main routes between Belfast and Lisburn until the opening of the present road via Dunmurry in the 1810s, making the bridge unnecessary before the canal was cut. A sketch by William Legge in 1816 shows the bridge much as it appears today, with timber spars depicted across the navigation arch at spring level, their purpose—whether vestiges of construction falsework or to maintain abutment spacing—uncertain. The navigation was officially abandoned for commercial traffic in 1956 but has been maintained as a recreational amenity. The bridge has group value with the adjacent former lock keepers house and is a striking feature of the riverscape, demonstrating considerable historical and industrial archaeological interest.