Pontwalby Railway Viaduct (partly in Blaengwrach community) is a Grade II listed building in the Neath Port Talbot local planning authority area, Wales. First listed on 30 January 2004. Viaduct.

Pontwalby Railway Viaduct (partly in Blaengwrach community)

WRENN ID
forgotten-pier-sage
Grade
II
Local Planning Authority
Neath Port Talbot
Constituency
Neath and Swansea East MP: Carolyn Harris (Lab)
Country
Wales
Date first listed
30 January 2004
Type
Viaduct
Address
Pontwalby Railway Viaduct (partly in Blaengwrach community), Glynneath
OS grid reference
SN 890 064
Coordinates
51.74581, -3.60827
Source
Cadw listing

Also on this page: flood risk · radon risk · weather exposure · detailed attributes ↓

Description

The Pontwalby Railway Viaduct is a railway viaduct constructed from squared sandstone blocks featuring tooled angles and voussoirs. It has five broad round arches, which are supported by massive tapering piers, the tallest of which rises over 18 meters high. Each pier is divided along the axis of the viaduct by a tall arched opening that also uses stone voussoirs. There is a bull-nosed string course located beneath the parapet, topped with flat stone coping. The fifth arch on the southwest side has been blocked with stone, featuring a large open roundel in the stonework that is surrounded by brick.

Local climate

Pontwalby Railway Viaduct (partly in Blaengwrach community) sits in one of the wettest parts of the UK, with an average of 1,300 mm of rain a year. This makes it wetter than 95% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 93% of listed buildings.

It experiences an average of 39 freeze-thaw cycles a year, more than 74% of listed buildings. Of these, 18 follow at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.3°C per decade since 1991.

Averages for 1991–2020; temperature trend 1991–2025. Figures describe the wider area (a grid cell of roughly 10 km), not the individual site. Contains modified Copernicus Climate Change Service information 2026.

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