Isallt-fawr is a Grade II listed building in the Snowdonia National Park local planning authority area, Wales. First listed on 19 January 1952. House.

Isallt-fawr

WRENN ID
night-foundation-plum
Grade
II
Local Planning Authority
Snowdonia National Park
Constituency
Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
Country
Wales
Date first listed
19 January 1952
Type
House
Address
Isallt-fawr, Dolbenmaen, Gwynedd
OS grid reference
SH 534 443
Coordinates
52.97659, -4.18477
Source
Cadw listing

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

Description

Isallt-fawr is a 17th century building located on a downhill site, constructed from long local rubble stonework with some boulders at the lower end. It features a slate roof and is one storey with attics, approximately symmetrical in design, consisting of three bays with deep fire bays at each end. The central entrance has a boarded door topped with a radial slate voussoir lintel and a drip ledge. The ground floor has six-paned windows with slate lintels, and a small fire window on the right; the upper floor contains four-paned windows, each set within a small gable. At the rear, there are two simple gabled dormers flanking a late 20th century rear wing. The lower gable end previously had four small windows on either side of the stack, all with projecting drip ledges, though only two of these windows remain. The building is supported by large boulder footings and has stone stacks with drip courses.

While not accessible during the inspection, it is believed that the main living room is located at the uphill end, featuring a winding stair beside a large gable fireplace, with a central hallway and a parlour at the lower end that has a window beside its large fireplace. The roof has been modernized.

Local climate

Isallt-fawr sits in one of the wettest parts of the UK, with an average of 1,550 mm of rain a year. This makes it wetter than 99% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 99% of listed buildings.

It experiences an average of 20 freeze-thaw cycles a year, fewer than 79% of listed buildings. Of these, 8 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
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  • Radon risk assessment
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  1. Carthouse, Stable and Granary at Isallt-fawr Grade II 25 m
  2. Cowhouse at Isallt-fawr Grade II 68 m
  3. Church of St Michael Grade II 838 m
  4. Tan-y-graig Grade II 939 m
  5. Pont Llanfihangel (aka Pont Llan) Grade II 983 m
  6. Pont Gyfyng Grade II 1.2 km
  7. Bryn-wern Grade II 1.4 km
  8. Twr Gwynllan Grade II 1.5 km
  9. Lodge Bridge Grade II 1.8 km
  10. Outfield yard group at Clenennau Grade II 1.8 km