Cymmer Viaduct is a Grade II listed building in the Neath Port Talbot local planning authority area, Wales. First listed on 31 July 2000. Engineering structure.

Cymmer Viaduct

WRENN ID
fading-turret-martin
Grade
II
Local Planning Authority
Neath Port Talbot
Constituency
Aberafan Maesteg MP: Stephen Kinnock (Lab)
Country
Wales
Date first listed
31 July 2000
Type
Engineering structure
Address
Cymmer Viaduct, Glyncorrwg
OS grid reference
SS 857 961
Coordinates
51.65236, -3.65248
Source
Cadw listing

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

Description

Cymmer Viaduct is a wrought-iron lattice-girder viaduct built with a slightly curved deck, aligned roughly north to south. The main abutments are made of coursed rock-faced stone and feature a round arch with a keystone, above which is a string course and a coped parapet. The arches are flanked by round turrets that rise to the full height of the parapets. On the northern side, the parapets curve outwards and end in square piers. The southern side has an additional abutment that supported a second girder bridge over the nearby former Rhondda and Swansea Bay Railway, which is now the Afan Valley Cycle Way.

The lattice girders rest on three tapering rectangular piers made of rock-faced stone with moulded copings. The girders are constructed in four straight sections and still have some timber cross members on the deck.

Local climate

Cymmer Viaduct sits in one of the wettest parts of the UK, with an average of 1,340 mm of rain a year. This makes it wetter than 96% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 95% of listed buildings.

It experiences an average of 33 freeze-thaw cycles a year, fewer than 53% of listed buildings. Of these, 15 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.

More on this building

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