Radon Gas and Property — What Buyers Need to Know
Radon is a naturally occurring radioactive gas that affects certain areas of the UK. It's invisible, odourless, and something every buyer in an at-risk area should check before exchange.
Free, no sign-up required — find out if your property is in a radon Affected Area in under a minute.
Radon is the second biggest cause of lung cancer in the UK after smoking, responsible for around 1,100 deaths per year. Most properties have entirely safe levels — but in certain geological areas, concentrations can be high enough to pose a real health risk. Knowing whether you're in one of those areas before you buy is simple, fast, and free.
What Is Radon and Where Does It Come From?
Radon is a naturally occurring radioactive gas produced by the decay of uranium and radium in rocks and soils — particularly granite, limestone, and certain sandstones. It seeps up through the ground and into buildings, where it can accumulate to harmful concentrations, especially in basements, ground floors, and poorly ventilated spaces.
In the open air, radon disperses harmlessly. The health risk arises when it becomes trapped inside a building and is inhaled over a prolonged period. Radon decays into radioactive particles that can lodge in lung tissue, and it is this long-term exposure that increases cancer risk.
The UK Health Security Agency recommends that radon levels should be reduced in any building where the annual average exceeds 200 becquerels per cubic metre (200 Bq/m³). This is known as the Action Level. Properties above this threshold should have radon reduction measures installed.
Radon Risk Levels Explained
The UKHSA and British Geological Survey (BGS) classify radon risk by the estimated percentage of homes in an area that are likely to be above the Action Level. This is expressed as a probability — not a certainty — for any individual property.
🟢 Below 1%
The vast majority of the UK falls into this category. Radon is present but almost certainly at safe levels. No action required and not classed as an Affected Area.
🟡 1% – 10%
Classed as a radon Affected Area. Testing is recommended. Elevated levels are possible but not certain. Straightforward remediation measures are available if needed.
🔴 Above 10%
Higher risk Affected Area. Testing is strongly recommended before exchange. Building regulations require radon protective measures in new builds in these areas.
Which Areas of the UK Are Most Affected?
Radon risk is directly linked to the underlying geology. Areas underlain by granite, limestone, and certain sedimentary rocks tend to have the highest radon potential. The table below summarises the main affected regions — but individual postcode risk can vary significantly within these areas.
| Region | Risk Level | Key Areas |
|---|---|---|
| Cornwall & Devon | High | Granite moorland — highest radon levels in England. Parts of Dartmoor, Bodmin Moor, Land's End. |
| Peak District & Derbyshire | High | Limestone areas around Buxton, Matlock, Hope Valley. |
| Northamptonshire | High | Ironstone geology across much of the county — one of the most affected areas outside the South West. |
| Somerset & Avon | Medium | Mendip Hills limestone and parts of the Bath area. |
| Lincolnshire & Yorkshire Wolds | Medium | Chalk and limestone upland areas. |
| Lake District & Cumbria | Medium | Granite and metamorphic rocks in upland areas. |
| Oxfordshire & Cotswolds | Medium | Jurassic limestone belt running through the region. |
| South Wales | Medium | Old Red Sandstone and limestone geology in parts of Powys and Brecon Beacons. |
| North West England | Low | Most of Greater Manchester, Merseyside, and Cheshire are low risk. Exceptions exist in upland areas. |
| West Yorkshire | Low | Generally low risk across the major urban areas. Some elevated risk in limestone dales areas. |
| West Midlands | Low | Most of the region is low risk. Parts of Worcestershire have slightly elevated geology. |
Source: UKHSA / BGS Indicative Atlas of Radon in Great Britain. This table provides regional guidance only — individual postcodes should always be checked using the official UKradon tool.
What Should You Do if Your Property Is in an Affected Area?
Being in a radon Affected Area does not mean the property has dangerous radon levels — it means testing is recommended. Follow these steps:
Check the postcode
Use the UKHSA's free postcode checker at ukradon.org to find out whether the property falls within a radon Affected Area. This takes under a minute and requires no registration.
Commission a radon test
If the property is in an Affected Area, commission a radon measurement test before exchange. This involves placing small detectors in the property for 90 days and returning them for laboratory analysis. Domestic test packs are available from UKHSA at modest cost including analysis.
Review the results
If the result is below 100 Bq/m³, no action is needed. Between 100–200 Bq/m³, measures are advisable. Above 200 Bq/m³ (the Action Level), remediation is recommended — and you should factor the cost into your negotiations.
If levels are high — remediate
Radon can typically be reduced to safe levels through straightforward building works — most commonly the installation of a radon sump beneath the floor. This involves drilling a small hole and fitting an electrically powered or passive fan. Cost varies depending on the property but is usually well within negotiating range on a purchase.
A radon test requires 90 days to complete accurately — ideally straddling both summer and winter months to get a representative annual average. If you're purchasing a property in an Affected Area and want a test result before exchange, start the process as early as possible. Alternatively, negotiate a price adjustment or retention to account for potential remediation.
Radon and Your Survey
A RICS Home Survey does not include a radon measurement — that requires specialist testing equipment over a 90-day period. However, your surveyor will:
- Note whether the property is in a known radon Affected Area
- Flag whether radon protective measures appear to be present in the construction
- Recommend specialist testing where appropriate
- Advise whether the property's construction type makes it more or less susceptible to radon ingress
Radon also features as a standard legal enquiry in property conveyancing. Local authority searches include a CON29 enquiry (3.13) which will confirm whether the property is in a radon Affected Area. However, this only tells you about the area — not the actual radon level in that specific building. A test is the only way to know for certain.
Frequently Asked Questions
Check Your Postcode Now
The official UKHSA radon checker is free, instant and requires no registration. Find out whether your property is in an Affected Area in under a minute.
Check on UKradon.org →UKHSA also offers full property-level radon reports at a modest fee from ukradon.org.
Buying in a Radon Area? Talk to Us.
CJ Bloor surveyors can advise on radon risk as part of your survey and help you understand the implications before you commit.
Explore our other free guides: View all property guides →
CJ Bloor Property Consultants Limited is regulated by RICS. All surveys are carried out in accordance with the RICS Home Survey Standard. Radon risk data sourced from the UKHSA / BGS Indicative Atlas of Radon in Great Britain. For the definitive risk report for your postcode, always refer to the official UKradon service.
