Strainer arches and retaining walls is a Grade II listed building in the Gwynedd local planning authority area, Wales. First listed on 21 July 2000. Retaining wall.

Strainer arches and retaining walls

WRENN ID
small-entrance-cream
Grade
II
Local Planning Authority
Gwynedd
Constituency
Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
Country
Wales
Date first listed
21 July 2000
Type
Retaining wall
Address
Strainer arches and retaining walls, Nantlle, Llanllyfni
OS grid reference
SH 501 532
Coordinates
53.05579, -4.23692
Source
Cadw listing

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

Description

This structure consists of two very high battered retaining walls made from coursed slate slabs. They feature a pair of slate strainer arches, which are arched both above and below with slate voussoirs, helping to hold the walls apart.

Local climate

Strainer arches and retaining walls 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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  • 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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