3.2 Site preparation – protection from radon gas
Radon is a naturally occurring, radioactive, colourless and odourless gas that is formed where uranium and radium are present. It can move through cracks and fissures in the subsoil, and so into buildings. The amount, or activity, of radon is measured in becquerels (Bq). Where this gas occurs under a dwelling, the external walls contain it and the containment of radon can build up inside the dwelling over the long term posing a risk to health.
Breathing in radon gas for long periods increases the risk of developing lung cancer and since people spend a high proportion of their time at home, concentration levels in dwellings are very important. Although the risk is relatively insignificant for people visiting or living for short periods in a dwelling with high levels of radon, long-term exposure can increase the risk to the point where preventative action is necessary. To reduce the risk, all new dwellings, extensions and alterations, built in areas where there might be radon concentration, may need to incorporate protective measures.
Public Health England (PHE), formally the Health Protection Agency, is the primary resource for advice about radon in the UK, and recommends that radon levels in homes should be reduced if the average is more than 200 becquerels per cubic metre (Bq/m3). Further information relating to radon levels, testing, sources and effects can be accessed on the PHE's "UKradon" website at http://www.ukradon.org/.
Conversions - in the case of conversions, as specified in regulation 4, the building as converted shall meet the requirements of this standard in so far as is reasonably practicable, and in no case be worse than before the conversion. (regulation 12, schedule 6).
“Radon probability areas” have been designated by testing dwellings. Where tests on existing dwellings show that 1% of the dwellings in that area are likely to have a radon concentration above 200 Bq/m3 (the action level) the area is designated as a ‘radon probability area’.
Radon maps - The Health Protection Agency (HPA) (now Public Health England (PHE)) and the British Geological Society jointly worked on detailing mapping in Scotland of radon potential. The report providing an overview of this work, titled "Indicative Atlas of Radon in Scotland", was published in July 2011 and is available to view or download from PHE's "UKradon" website http://www.ukradon.org/. The resulting high definition digital map indicates areas in Scotland with elevated radon potential. The map provides an indicative picture of areas of the country where radon levels are likely to be higher.
Radon risk report - the atlas presented in the report contains simplified maps that are indicative rather that definitive with each 1km grid square coloured according to the highest radon potential found within it. A risk report giving the estimated radon potential for an individual dwelling or site can be obtained through the "UKradon" website http://www.ukradon.org/.
If a dwelling is to be located or extended on ground designated as a ‘radon probability area’, or on ground where radon is known to exist, protective work should be undertaken to prevent excessive radon gas from entering the dwelling.
Radon protective measures should be provided in accordance with the guidance contained in BRE publication BR 211 – ‘Radon: guidance on protective measures for new buildings’.
Additional guidance on the installation of radon protection measures in dwellings is available in two BRE Good Building Guides; GG 73 "Radon protection for new domestic extensions and conservatories with solid concrete ground floors" and GG 74 "Radon protection for dwellings". Both of these publications should be read in conjunction with BR 211.