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Hengoed Viaduct

A Grade II* Listed Building in Ystrad Mynach, Caerphilly

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Latitude: 51.6467 / 51°38'48"N

Longitude: -3.2218 / 3°13'18"W

OS Eastings: 315560

OS Northings: 194920

OS Grid: ST155949

Mapcode National: GBR HW.7GBB

Mapcode Global: VH6DF.3WM0

Entry Name: Hengoed Viaduct

Listing Date: 31 July 1980

Last Amended: 10 September 1999

Grade: II*

Source: Cadw

Source ID: 22325

Building Class: Transport

Location: A prominent landscape feature spanning the Rhymney valley between Maesycwmmer and Hengoed.

County: Caerphilly

Town: Caerphilly

Community: Maesycwmmer (Maes-y-cwmwr)

Community: Maesycwmmer

Built-Up Area: Ystrad Mynach

Traditional County: Monmouthshire

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The Hengoed Viaduct was built as part of the Newport, Abergavenny and Hereford (Taff Vale Extension) Railway. The engineer was Charles Liddell. It was a standard gauge line linking Pontypool with the Taff Vale Railway at Quakers Yard, but was proposed as part of a strategic lateral route to Swansea. The railway was begun in 1847, was completed as far as Quakers Yard in 1858, and Swansea in 1864. The line was taken over by the GWR in 1865 and was rich in both passenger and freight traffic. It was closed over 100 years later in 1964.

The cross-valley line required substantial engineering works: 3 viaducts, 4 tunnels, embankments and steep gradients, all constructed under the railway engineer, Charles Liddell. The cast iron Crumlin Viaduct was a structure of major significance, but only the abutments survive. The engineer's drawing for the Hengoed Viaduct is dated 1857 and it was built by Messrs Rennie & Logan at a cost of £20,000. It was designed to be 130 feet (39.6 metres) high and it was more traditional in style than the Crumlin Viaduct using stone from the nearby Trecelyn quarries and local bricks. The smaller arch at the east end passed over the Brecon & Merthyr Railway.


High 16-arch viaduct, slightly curved in plan. Constructed of rock-faced, snecked Pennant sandstone. High round arches on imposts with large voussoirs. Soffits partly of red brick. Narrow, slightly splayed piers. String course and shallow parapets with coping stones, some upright. Square piers to ends and flanking smaller E arch which is skewed.

Reasons for Listing

Listed grade II* as a major monument of railway engineering on a strategic lateral route, in use for over 100 years and one of the oldest surviving viaducts of its type. Group value with the Woollen Mill which stands beneath.

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