Indicated — Lucan AND Pettycanon,laraghcon

One of three bridges spanning the River Liffey in Lucan. The present Lucan Bridge which spans the River Liffey was built in 1814 to replace an earlier bridge (DU017-019007---) located downriver 160m to the W which in turn was built in the 18th-century to replace the medieval bridge (DU017-016----) located 240m to the W. The 19th-century bridge was described by the National Inventory of Architectural Heritage (NIAH) as a; 'Single-arch road bridge over river, 1814. Coursed squared limestone walls and abutments. Segmental arch with slender ashlar voussoirs and double keystone. Cast-iron balusters to parapet with stone coping' (www.buildingsofireland.ie; NIAH Reg. No. 11201090). No bridge is shown at this location of Rocque's 1760 Map of County Dublin. This bridge was described by Simington and O'Keeffe (1991, 270-4) as 'the longest span masonry arch ever built in Ireland. There is one clear-cut and informative mention by Bernard Mullins in his presidential address to ICEI in 1859; "this structure, consisting of a single arch' of 111ft [33.8m] span and 22ft [6.7m] rise, like many of the same period, is of a far more expensive character than the occasion called for. Its construction was attended with no difficulty, a good foundation having been easily obtained, with suitable materials immediately at hand, and yet the cost of construction exceeded £9,000. Mr George Knowles was the architect and, probably, the contractor, an arrangement common in those days, owing to the difficulty of obtaining the services of a sufficiently competent person of the latter class, together with the want of capital, there having been no banks to assist enterprise of that description". The date of its erection was solved by de Courcy who found that the metal balustrades were made by the Phoenix Iron Works of Dublin in 1814. Lucan is a segmental arc with a rise-to-span ratio of 0.20, whereas Sarah [Bridge] is three-centred, perhaps oval, with a ratio of 0.29; Lismore is 0.2. The ashlar masonry in Lucan is superb and the see-through iron balustrade parapets and unobtrusive spandrels give it a superb overall appearance from the river. The skewback, resting on an impost, is formed of three stones with a springing face at 45° to the horizontal. This is unusual for such a large arch; however, the springings are backed each side by solid 6ft [1.8m] thick pier abutments up the road level, giving a large vertical load; more-over, it springs from less than 3ft [0.9m] above the solid rock; consequently there is little risk of horizontal slippage resulting from the horizontal component of the arch thrust. This, of course, has been proved over a service life of 176 years. The actual span was checked by Dublin Co. Council in 1990 and is 110ft [33.5m].' Compiled by: Caimin O'Brien Date of upload: 8 May 2023