Radon Gas in Homes, Which Areas Are Affected and What to Do
Radon is a naturally occurring radioactive gas that can accumulate in homes across parts of England and Wales. Understanding your property's risk level is an important step before buying.
Published: 16 Mar 2026 · Updated: 16 Mar 2026 · 6 min read
What is Radon Gas?
Radon is a naturally occurring radioactive gas produced by the decay of uranium in rocks and soils, particularly granite and certain sedimentary formations. It is colourless, odourless, and tasteless, entirely undetectable without specialist testing. Radon rises from the ground and disperses harmlessly outdoors, but in enclosed spaces such as homes and workplaces it can accumulate to levels that pose a health risk.
The UK Health Security Agency (UKHSA) identifies radon as the second-largest cause of lung cancer in the UK after smoking, responsible for an estimated several thousand deaths per year nationally.
Which Areas Are at Risk in England and Wales?
Radon levels vary significantly by geology. The UKHSA publishes a national radon map dividing the country into Affected Areas, defined as postcodes where 1% or more of homes are estimated to have radon levels at or above the Action Level (currently 200 Becquerels per cubic metre, Bq/m³).
Higher-risk areas include:
| Region | Geology |
|---|---|
| Cornwall and Devon | Granite batholiths |
| Parts of Somerset and Dorset | Limestone and mudstone |
| Derbyshire and parts of the Peak District | Limestone |
| Northamptonshire and parts of Leicestershire | Ironstone and limestone |
| Parts of Wales | Granite and slate |
| Lincolnshire and parts of Yorkshire | Limestone |
However, radon is not exclusively a rural problem, some urban properties in affected geologies can also have elevated levels. The only reliable way to assess a specific property is to carry out a measurement test.
How is Radon Measured?
Radon is typically measured using passive detector devices (small charcoal or electret devices) placed in the lowest occupied rooms of a property for a period of at least three months, ideally over winter when homes are more enclosed. Results are expressed in Bq/m³.
- **Below 100 Bq/m³**, No action required
- **100–200 Bq/m³**, Consider remediation; above the UK Target Level
- **Above 200 Bq/m³**, Action required; above the Action Level
Testing kits are available directly from the UKHSA Radon Survey team and from accredited private laboratories. Costs are typically modest for a pair of detectors covering ground and first floor.
Buying a Property in a Radon Affected Area
When purchasing a property in a known radon area, consider the following steps:
- Ask your solicitor to carry out a radon search as part of the conveyancing process (specialist environmental search providers include this)
- Commission a radon test before exchange where possible, particularly for ground-floor and basement properties
- Ask the seller whether any previous radon tests have been carried out and whether remediation works have been installed
Radon Remediation
If a property tests above the Action Level, radon remediation is usually straightforward and effective. The most common solution is a positive pressurisation or sub-slab depressurisation system, essentially a small fan that draws radon from beneath the floor and vents it to the outside. Costs typically range from a few hundred to a few thousand pounds depending on the property type and the system required.
New-build properties in Affected Areas are required by Building Regulations to incorporate radon-protective measures during construction.
Property Passport UK displays radon Affected Area status for properties it indexes, helping buyers understand the geological context of a property before committing to purchase.
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