Radon Gas Levels by Postcode: Is This an Affected Area?

Enter a postcode to read the indicative radon class for the area from the UK Health Security Agency (UKHSA) radon map, the official source for radon potential in the UK, produced with the British Geological Survey. The class describes the chance that homes in the mapped area have radon above the 200 Bq/m³ Action Level; it is not a measurement inside any particular house. Use it to decide what to ask the seller about existing tests, whether to commission a three-month measurement, and what mitigation would cost if the result came back high. This screen is on screen with no signup and is not an insurance or mortgage decision.

No signup. Postcode-area screen of the UKHSA/BGS Indicative Atlas of Radon, published under the Open Government Licence v3.0. Great Britain only.

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How the radon map works

The UKHSA radon map, produced with the British Geological Survey, divides Great Britain into 1 km squares and estimates for each the percentage of homes likely to exceed the 200 Bq/m³ Action Level. Squares at 1% or more are radon Affected Areas; the class shown by this checker is that banding for the postcode's square. Radon comes from the natural decay of uranium in rocks and soil, so the highest classes follow geology: the granites of Devon and Cornwall and Aberdeenshire, the limestones of Somerset, the Peak District and North Yorkshire, the ironstones of Northamptonshire, but the class describes an area, and two neighbouring houses can measure very differently.

Keep map potential and indoor measurement separate

The class here applies to an area; only measurement in the building establishes its indoor level. UKHSA's standard test is two passive detectors over three months. If the seller has tested, ask for the report and any mitigation documents; if not, decide whether to make a test a condition, negotiate a retention in a high-class area, or test after moving in. A missing map response on this page is unknown, not low.

What a high reading leads to

Radon is estimated by UKHSA to be linked to around 1,100 lung-cancer deaths a year in the UK, the largest cause after smoking, and the risk rises with long-term exposure. The fixes are well established and comparatively inexpensive: a sump and fan beneath the floor slab vented above roof level, positive-pressure ventilation, better under-floor ventilation, and sealing. See the cost ranges in the questions below. Record the test date, the rooms tested and any re-test after mitigation, and keep them with the property's papers.

Where this fits with the other ground checks

Radon class is one of four ground signals we read for an area; compare it with the separate ground-stability result and the coal mining search, or browse the radon area guides by outcode. Complete (£24.99) includes the available area records in the wider property report; it does not perform an indoor test. Check your chosen address.

Frequently asked questions

Is the radon band an indoor gas reading?
No. The indicative map groups areas by radon potential. Only measurement in the building can establish its indoor radon level.
What should I ask a seller after a higher-band result?
Ask whether the property has been tested, request the report and any mitigation documents, and check the current UKradon guidance on measurement. A map result alone does not establish whether remedial work is needed.
What is the radon Action Level in the UK?
UKHSA sets the UK Action Level at 200 becquerels per cubic metre (Bq/m³) of indoor air, above which remedial action is recommended, and a Target Level of 100 Bq/m³ as the ideal outcome for new and remediated homes. The average UK indoor level is around 20 Bq/m³. A radon Affected Area is one where UKHSA estimates at least 1% of homes exceed the Action Level. The map class on this page is the area's banding on that scale.
How do I test a home for radon?
The standard UKHSA measurement is two passive detectors (one in the main living room, one in an occupied bedroom) left in place for three months and posted back for analysis, which averages out daily and seasonal swings. Detector packs are ordered through UKradon for a modest fee. Short-term electronic monitors give an indication in days but are less reliable than the three-month average. During a purchase, ask the seller for any existing result via the TA6 form; a three-month test rarely fits the transaction, so many buyers test after completion and mitigate if needed.
How much does radon mitigation cost?
Typical contractor quotes: a radon sump with a fan (the most effective fix, often cutting levels by 90% or more) roughly £800–£1,500; positive-pressure ventilation roughly £500–£800; improved under-floor ventilation roughly £200–£500; sealing floors and service gaps roughly £100–£300, usually as a supplementary measure. Running cost for a sump fan is a few pounds a month. Re-test after the work to confirm the level has fallen.
Does radon affect a mortgage or home insurance?
Radon is a health matter, not a structural one, so it does not normally feature in lending or buildings-insurance decisions in the way flood or subsidence do. Confirm with your own lender and insurer rather than relying on that as a rule. Where it does matter is at resale: a documented test result, and mitigation with a post-works re-test, reassures the next buyer.
Are new-build homes protected against radon?
In England and Wales, Building Regulations Approved Document C requires radon protection in new buildings in affected areas: basic protection (a radon-proof membrane across the ground floor) where 3–10% of homes are estimated to exceed the Action Level, and full protection (membrane plus a sump that can be activated later) where more than 10% do. Check the building-control completion certificate and ask the developer which level was installed.

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