Glasinfryn Viaduct (partly in Llandygai community) is a Grade II listed building in the Gwynedd local planning authority area, Wales. First listed on 22 September 1997. Viaduct.

Glasinfryn Viaduct (partly in Llandygai community)

WRENN ID
watchful-crypt-thunder
Grade
II
Local Planning Authority
Gwynedd
Constituency
Bangor Aberconwy MP: Claire Hughes (Lab)
Country
Wales
Date first listed
22 September 1997
Type
Viaduct
Address
Glasinfryn Viaduct (partly in Llandygai community), Bangor, Pentir
OS grid reference
SH 587 690
Coordinates
53.20007, -4.11663
Source
Cadw listing

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

Description

Glasinfryn Viaduct is a structure made of rock-faced coursed stone, extending for about 120 meters along a distinct curve. It features eight arches, including a broad central semi-elliptical skewed arch that has five-ring dry-toothed blue brick voussoirs. This central arch is flanked by narrower semi-circular straight arches, with four on one side and three on the other. At the base, there is a margin-dressed rock-faced string course that supports a parapet made of five courses, which is coped with hog-backed stone.

Local climate

Glasinfryn Viaduct (partly in Llandygai community) sits in one of the wettest parts of the UK, with an average of 1,210 mm of rain a year. This makes it wetter than 92% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 90% of listed buildings.

It experiences an average of 37 freeze-thaw cycles a year, more than 67% of listed buildings. Of these, 19 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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