Tunnel Portal and Tunnel is a Grade II listed building in the Gwynedd local planning authority area, Wales. First listed on 21 July 2000. Tunnel.

Tunnel Portal and Tunnel

WRENN ID
burning-porch-hemlock
Grade
II
Local Planning Authority
Gwynedd
Constituency
Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
Country
Wales
Date first listed
21 July 2000
Type
Tunnel
Address
Tunnel Portal and Tunnel, Nantlle, Llanllyfni
OS grid reference
SH 498 534
Coordinates
53.05678, -4.24191
Source
Cadw listing

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

Description

The eastern tunnel portal is constructed from squared slate rubble and features a semi-circular arch made of slate voussoirs. Above the arch, there is a string course and a parapet. The tunnel itself was not inspected during the survey.

Local climate

Tunnel Portal and Tunnel sits in one of the wettest parts of the UK, with an average of 1,380 mm of rain a year. This makes it wetter than 97% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 98% of listed buildings.

It experiences an average of 25 freeze-thaw cycles a year, fewer than 73% of listed buildings. Of these, 12 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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  • No EPC on record for this property
  • No sale records on file
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  • Detailed attributes — period, style, materials, features
  • Flood risk assessment
  • Radon risk assessment
  • Weather exposure and heating demand — rain and frost month by month and year by year, wind direction, solar and humidity
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