Alcatraz is a Grade II listed building in the Gwynedd local planning authority area, Wales. First listed on 1 June 1949. House.
Alcatraz
- WRENN ID
- solitary-chalk-rook
- Grade
- II
- Local Planning Authority
- Gwynedd
- Constituency
- Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
- Country
- Wales
- Date first listed
- 1 June 1949
- Type
- House
- Address
- Alcatraz, 18 Gaol Street, Pwllheli
- OS grid reference
- SH 373 351
- Coordinates
- 52.88881, -4.4185
- Source
- Cadw listing
Description
Alcatraz is a long, low, two-storey building dating from the 19th century. It features a rendered front with a scribed cement finish on No 20 and a painted plinth on Alcatraz. The building has a steep old slate roof with overhanging eaves and rubble chimney stacks, although the stack for No 16 has been removed. The chimney for No 18 is particularly tall and has been heightened with brick. Alcatraz has prominent modern blinds, and the first floor primarily consists of 16-pane sash windows, while No 16 has one sash window on the ground floor, with fixed glazed windows and small panes on No 20. The doors are modern, half-glazed, and boarded.
The right-hand gable end is made of rubble, and the rear has an undulating slate roof that backs onto the burial ground of Penlan Chapel.
Internally, the buildings have been significantly modernised, and the dividing wall between Nos 14 and 16 has been removed.
Local climate
Alcatraz sits in one of the wettest parts of the UK, with an average of 1,670 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 4 freeze-thaw cycles a year, fewer than 98% of listed buildings. Of these, 1 follows 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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- Full EPC report — heating system, energy costs, size, glazing, construction etc.
- No sale records on file
- No related consent applications matched
- 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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