Mill Forge is a Grade II listed building in the Caerphilly local planning authority area, Wales. First listed on 18 July 2001. Forge.

Mill Forge

WRENN ID
secret-frieze-thyme
Grade
II
Local Planning Authority
Caerphilly
Constituency
Caerphilly MP: Chris Evans (Lab)
Country
Wales
Date first listed
18 July 2001
Type
Forge
Address
Mill Forge, Ystrad Mynach, Gelligaer
OS grid reference
ST 145 929
Coordinates
51.6291, -3.23559
Source
Cadw listing

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

Description

Mill Forge is a forge building that is attached to the left side of a house and shares the same chimney. It is constructed of limewashed stone rubble and features a corrugated roof with a ridge ventilator, topped with a weathervane. On the right side, flush with the house, there is a cambered-headed window with a shutter. The doorway is located centre right, accessed by two steps, and the wall projects and extends to the left. The main entrance is now located in the gable end, and there is a blocked doorway to a former cowshed nearby. The house attached to the right has been altered and extended, featuring a two-window range on the frontage with a central porch on the ground floor and flat roof dormers above, all dating from the 20th century, along with end stacks.

Inside the forge, the hearth is situated in the wall shared with the house and has a cambered arch reinforced with iron, with round-arched recesses below. The chimney breast is stepped and curved to accommodate the bellows, which now hang on the rear wall. In the cottage, the fireplace includes a bake oven.

Local climate

Mill Forge sits in a wetter-than-average part of the UK, with an average of 1,060 mm of rain a year. This makes it wetter than 85% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 81% of listed buildings.

It experiences an average of 32 freeze-thaw cycles a year, fewer than 59% of listed buildings. Of these, 13 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
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