Radon is a natural gas that seeps from the ground into buildings, and whether a property sits in a radon “Affected Area” can come up during a house purchase. The UK Health Security Agency (UKHSA) runs the UKradon service, publishes the radon map with the British Geological Survey, and gives specific advice to buyers and sellers. This article summarises the UKradon pages on buying and selling, radon searches, the Action Level and UK maps, plus UKHSA’s 2022 press release on the updated map. It covers England, Wales, Scotland and Northern Ireland and says where the sources separate them. It is general information about property moves, and it does not describe conveyancing practice in Scotland.
What radon is and how big the risk is
UKradon describes radon as a colourless, odourless radioactive gas formed by the decay of small amounts of uranium that occur naturally in all rocks and soils. Every building contains radon but the levels are usually low, and the chances of a higher level depend on the type of ground. UKHSA’s 2022 press release says the risk of developing lung cancer from exposure to radon remains low for most people and that the vast majority of buildings are outside Affected Areas. It adds that the risk is highest among smokers and ex-smokers.
The map and what “Affected Area” means
UKHSA says its map shows where high levels are more likely: the chance is less than one home in a hundred in the white areas and greater than one in three in the darkest areas. UKradon adds that the map should not be used for basements, cellars or underground sites, which should be treated as having an increased chance of high radon regardless of location. The map was updated in England, Wales and Scotland in December 2022, while the Northern Ireland map, last updated in 2015, was unchanged.
An Affected Area is one where UKHSA advises testing. UKradon’s flow chart for buyers says that if a property is not in an Affected Area there is no formal advice to test, meaning less than a 1% chance of a high radon level there. Its radon searches page shows that testing is advised for areas with a probability band of 1 to 3% and above.
Address searches
UKradon distinguishes definitive from indicative searches. Definitive searches use the full data set of 25-metre squares. An individual address search, for homes and small workplaces no larger than 25 metres in any direction, is available from the UKradon site for a fee of £3.90 and reports the estimated probability of being above the Action Level. For large buildings and land, the British Geological Survey offers a search for around £50 each.
The Action Level and the test
UKHSA recommends that radon levels be reduced in homes where the average is more than 200 becquerels per cubic metre (200 Bq m-3), a recommendation the UKradon page says has been endorsed by the Government. Because the Action Level is an annual average, measurements use two detectors, one in a bedroom and one in a living room, over three months to average out short-term fluctuations. A Target Level of 100 Bq m-3 is described as the ideal outcome of remedial work, and UKradon says action should be considered if a result falls between the Target and Action Levels.
Advice for buyers and sellers
UKradon’s advice for buyers in an Affected Area is to ask the current owners whether they have completed a three-month radon test and, if so, to ask for a copy of the report. If not, buyers should discuss a retention with their solicitor and test after moving in. Sellers are advised to find any earlier test result, and if they have not tested, they should expect the new owner to be advised to test on moving in. Both should be prepared for questions about a retention.
Retentions
The page defines a retention as a sum held back from the sale to help pay for remedial work. It gives the typical remediation cost as £1,000 and a typical retention as between £800 and £3,000. The money is initially held by one of the solicitors for six months, to allow for moving in, the three-month test and receipt of the report. If the result is below the Action Level the money goes to the seller. If it is higher, the money pays for remedial works, with a timescale agreed for the work and a further test, and any surplus goes to the seller. UKradon says a retention may not suit buyers planning major building work on moving in or not moving in straight away.
New builds
For new homes, UKradon says radon protective measures are expected in Affected Areas where required by building regulations and guidance. Basic protection is a damp-proof membrane modified and extended into a radon-proof barrier across the ground floor. Full protection adds a radon sump or a ventilated subfloor void, and the sump is capped and not activated when the house is built. UKradon says buyers can ask the builder or use a radon search to find whether basic or full protection is expected. It also says Public Health England (PHE) recommends a three-month test during the first year of occupation because a result below the Action Level is not guaranteed. Where a result is above the Action Level, the options include adding a fan to the sump or increasing subfloor ventilation, followed by a further test.
Different building rules by nation
The searches page’s table shows the building-control category depending on the probability band. In the 3 to 10% bands, for example, England and Wales use “Basic” protection, Scotland “Stage 1” and Northern Ireland “Zone 1”; above 10% they use “Full”, “Stage 2” and “Zone 2”.
The bottom line
For a move, UKHSA’s advice is simple: check the map or run an address search, ask for any three-month test, agree with the solicitor whether to hold a retention, and test after moving in if there is no result. The Action Level is 200 Bq m-3 as a three-month, two-detector average, and new builds in Affected Areas should be tested in their first year.