Radon is a naturally occurring radioactive gas from the ground. It is colourless and odourless, so its presence cannot be identified during a visual inspection. UKHSA and the British Geological Survey publish mapping that indicates where buildings are more likely to have elevated levels, helping buyers decide whether measurement is advised.
A search result for a radon affected area does not state the measured level in one particular home. Conversely, a house that looks dry and well ventilated cannot be assumed to have a low level. Testing and a home survey answer different questions and should not be treated as substitutes.
What mapping tells you
Radon potential mapping combines geological information with a large database of building measurements. It identifies likelihood across an area rather than forecasting an individual result. Search reports may assign a potential band and recommend testing. Use the current official service or data referenced by your conveyancer.
Why measurement matters
Actual indoor concentration is influenced by geology, construction, ventilation and how the building is used. UKHSA advises testing in affected areas. Standard domestic measurement normally takes place over a period rather than through a brief reading at a viewing, because levels vary with weather and occupation.
What the surveyor can observe
The surveyor can describe relevant construction, such as basements, suspended floors or visible ventilation, and may recommend following the search result. The inspection does not measure radon, verify membranes beneath floors or test mechanical systems. Concealed protective measures require documentation or specialist investigation.
Transactions and records
Ask whether the property has been tested and request the complete result, test dates and details of any mitigation. Your conveyancer can advise on the search and contractual enquiries. If testing cannot be completed before exchange, discuss available arrangements with the conveyancer and a radon specialist rather than relying on a verbal promise.
If an elevated result is found
UKHSA guidance describes measures that can reduce levels, with suitability depending on the property. The response should follow a validated measurement and an assessment of construction. Retesting is important after work. A general surveyor can comment on visible condition but should not design a radon system without the relevant competence.
Possible approaches work by reducing entry or changing pressure and ventilation, but their practicality depends on floors, voids and occupancy. Any installation may require power, maintenance and clear discharge positions. Keep the baseline result, design details, commissioning information and follow-up measurements so future occupants can understand performance. If the layout or ventilation later changes, consider whether new measurement is appropriate rather than assuming the original result still represents the home.
- Use an approved long-term measurement approach
- Place detectors as instructed
- Do not infer a result from neighbouring homes
- Retest after mitigation or major alteration
Advice for your property
Get the right professional inspection
Online guidance is useful, but it cannot account for the construction, condition and history of an individual property. Tell us what you are buying or need valued and we will explain the appropriate service.
Authoritative sources and further reading
The guide is general information, not property-specific, structural, legal, tax or financial advice. Source pages can change; consult the relevant professional for your circumstances.