Radon Gas Check
Check any UK property for radon gas risk. Radon is a naturally occurring radioactive gas and the second leading cause of lung cancer in the UK — check before you buy.
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Radon Gas FAQ
What is radon gas?
Radon is a naturally occurring radioactive gas produced by the decay of uranium in rocks and soil. It seeps into buildings through foundations and can accumulate to dangerous concentrations indoors. It is odourless, colourless, and tasteless — undetectable without specialist testing.
Where is radon risk highest in the UK?
Radon levels are highest in areas with granite and limestone geology — including Devon, Cornwall, Somerset, Derbyshire, Northamptonshire, and parts of Scotland and Wales. The UK Health Security Agency (UKHSA) publishes radon potential maps based on geological surveys.[2]
Does radon affect property value or mortgages?
High radon levels can affect property value and some lenders may require evidence of remediation in high-risk areas. Sellers should disclose known radon issues on the TA6 form. Remediation — typically a sump pump or underfloor ventilation — costs £500–£2,500.
What radon level is safe?
The UK action level is 200 Bq/m³[1] (becquerels per cubic metre). Properties above this level should be remediated. The target level for new buildings is below 100 Bq/m³. A professional radon test (typically 3 months with a passive detector) gives an accurate reading.
Do sellers have to disclose radon risk?
Sellers complete a TA6 form covering environmental hazards, but many are unaware of their radon class. Always run an independent check in high-risk areas before exchange.
How much does radon remediation cost?
Remediation typically costs £500–£2,500. The most common approach is a radon sump — a pump installed beneath the floor slab that draws radon out before it enters the property.
Sources
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What is a radon gas check?
A radon gas check looks up the radon potential class for a specific property based on its 1 km Ordnance Survey grid square. The class (1–7) reflects the estimated percentage of homes in that area that, if tested, would be above the UK action level of 200 Bq/m³. Homedata combines British Geological Survey geological data with UK Health Security Agency measurement data to return an instant risk reading for any UK property.
How radon enters homes
Radon forms underground as uranium in soil and rock decays. It rises through the ground as a gas and enters buildings through cracks in floors, gaps around pipes, and through permeable building materials. Once inside, it can accumulate — particularly in basements, ground floors, and properties with poor underfloor ventilation. Newer buildings generally have better sealing, but even post-2000 homes in high-radon areas may require protective measures.
The highest concentrations in the UK occur over granite and limestone geology. Devon and Cornwall have the highest proportion of homes above the action level, followed by parts of Somerset, Derbyshire, Northamptonshire, and Lincolnshire. Parts of Scotland — particularly Aberdeenshire — also have elevated radon levels.
Why radon matters when buying property
Radon is the second leading cause of lung cancer in the UK, responsible for around 1,100 deaths per year according to UKHSA. Long-term exposure to elevated levels is a genuine health risk — yet it is entirely invisible without testing.
From a property perspective:
- Insurance and lenders. Some lenders in high-radon areas request evidence of testing or remediation before lending. This is most common for Zone 3+ radon potential areas.
- Building regulations. New homes built in high-radon areas (Radon Class 3+) are required to include protective measures under Part C of the Building Regulations. Retrofit protection on older properties typically costs £500–£2,500.
- Seller disclosure. The TA6 form asks sellers about environmental hazards, but many sellers have never tested for radon and cannot answer accurately. An independent check is the safest option.
Data source: British Geological Survey (BGS) and UK Health Security Agency (UKHSA), published under the Open Government Licence. Last reviewed: May 2026.