The Folly Arch is a Grade II* listed building in the Welwyn Hatfield local planning authority area, England. First listed on 6 February 1952. Gateway.
The Folly Arch
- WRENN ID
- sombre-gargoyle-coral
- Grade
- II*
- Local Planning Authority
- Welwyn Hatfield
- Constituency
- Welwyn Hatfield MP: Andrew Lewin (Lab)
- Country
- England
- Date first listed
- 6 February 1952
- Type
- Gateway
- Address
- The Folly Arch, Hawkshead Lane, North Mymms
- OS grid reference
- TL 254 030
- Coordinates
- 51.71197, -0.1855
- Source
- Historic England listing
Description
The Folly Arch is a gateway and folly located in Brookmans Park, North Mymms, which was formerly the southern entrance to the Gobions houses, demolished in 1836. It was built around 1740 for Sir Jeremy Sambrooke, likely designed by James Gibbs. The structure is made of red brick and features a large round-headed arch flanked by thin square turrets that are battlemented. The arch is adorned with rusticated voussoirs, while the turrets are divided into three stages and include slit windows set in deep chamfered surrounds with gauged brick heads. The design includes three floor bands and a modillioned cornice that imitates machicolation. The Folly Arch holds significant landscape value.
Local climate
The Folly Arch sits in one of the driest parts of the UK, with an average of 700 mm of rain a year. This makes it drier than 91% of listed buildings in the UK. Its exposure to wind-driven rain is lower than that of 90% of listed buildings.
It experiences an average of 33 freeze-thaw cycles a year, fewer than 54% of listed buildings. Of these, 15 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.
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- No EPC on record for this property
- 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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