Radon in conveyancing

    Radon is not a subject which springs to mind as an important consideration when buying or renting a property. However, it is an important subject and has serious implication if not treated. It is a stealthy substance which can seep into any type of building unnoticed and undetected. The sting in its tail is its radioactive properties which can cause lung cancer. The government has issued guidance on dealing with radon and property lawyers have an important role in ensuring that their clients are fully advised on this issue.

    Standard enquiry 3.13 in the new 2002 edition of CON 29 Part 1, Standard Enquiries of Local Authority is the starting point for elucidating information about radon. It asks whether the property is in a Radon Affected Area. But where does radon come from? What is a Radon Affected Area? What implications does a positive answer to the enquiry have? How can the property lawyer deal with radon in practice? This article aims to answer these questions and give some practical advice and guidance.

    Radon and lung cancer

    Radon is a radioactive gas which is created by the decay of naturally occurring uranium in rocks and soil1. Many people have heard of radon occurring in Cornwall, Devon and Somerset, but it is not restricted to these counties and levels can be high enough to cause concern inside properties anywhere in the UK. Because radon is a gas, it can seep out of the soil and into buildings through small cracks in the flooring, through gaps around pipes and cables and between joints2. Once inside, it gets trapped because the air pressure is generally slightly lower inside a building than outside. In this way, harmful concentrations can build up.

    Radon emits a type of radioactivity called alpha particles which can cause lung cancer by damaging the DNA inside cells when breathed in3. It is believed to be the second greatest cause of lung cancer in the UK after smoking4.

    Radon concentration is measured in units of Becquerels per cubic metre of air (Bq m-3). This is a measure of how many radon atoms in each cubic metre of air are undergoing radioactive decay and emitting alpha particles each second. The average level in UK homes is 20 Bq m-3. To reduce the risk to health, the government has set a Radon Action Level of 200 Bq m-3 and recommends people to take positive steps to reduce the level in their homes below this. For employers, the level above which action must be taken is 400 Bq m-3.

    The National Radiological Protection Board (NRPB) has estimated2 that living in a house with radon at the Action Level increases a person’s lifetime risk of developing lung cancer ten-fold compared to living in a house with an average concentration. Radon has a greater effect on people who smoke, and their risk of developing lung cancer is estimated as ten times higher than non-smokers5.

    Standard enquiry 3.13 asks whether the property is in a Radon Affected Area. Radon Affected Areas are defined as areas in which the NRPB estimates that 1% or more of homes have a level of radon above the Radon Action Level of 200 Bq m-3. It is important to appreciate that the answer to enquiry 3.13 is not based upon an actual measurement in the property of interest. It is an estimate from the NRPB based on a statistical analysis of results from homes in that area which have been tested. Another fact to appreciate is that radon levels can vary dramatically between neighbouring buildings, depending partly upon the level of ventilation.

    The NRPB has produced a useful colour coded radon map of the UK, which shows the estimated percentage of homes in any area which are predicted to be above the Radon Action Level6.

    Another comprehensive source of information is the Radon Atlas of the UK, which is available from the NRPB and can also be accessed free online7. It contains larger scale, colour coded maps of England and Wales to show the percentage of homes estimated to be above the Radon Action Level. There are also tables of data from over 400,000 actual measurements taken in homes. For ease of reference, these tables are sub-divided into authorities and post-code areas. However, although the tables contain measured values, this information will only ever be a general guide, as the data is anonymised and does not reveal the actual radon level within any individual property.

    What to do if the property is in a Radon Affected Area

    Where the answer to enquiry 3.13 is yes, the property is within a Radon Affected Area, the property lawyer should make some further pre-contract enquiries of the present owner or landlord8,9:

    • Has the radon level in the property been measured?

    • What was the result?

    • If the level was at or above the Radon Action Level, were remedial measures installed?

    • Was the effectiveness of the remedial measures established by re-measuring the radon level after completion?

    The potential purchaser or lessee should be informed of the situation in the report on title. Where the radon level has not previously been determined, or has not been measured since remedial measures were taken, the client should be advised to test the level themselves. The lawyer should also consider negotiating a radon bond (see later).

    If the property is a new one, the builder should be asked whether protective measures were incorporated into the building.

    If the answer to question 3.13 is negative, this will be a relief, but remember that this does not tell you that the radon concentration in that property is definitely below the Radon Action Level. It only means that the NRPB estimates that over 99% of homes in that area will be below this level. In this situation, there is no need to highlight the issue in the report on title, unless this is something the client is particularly concerned to find out about.

    How to measure radon levels

    How would somebody go about measuring the radon level in their home? Unfortunately, this is not straightforward because the levels fluctuate quite dramatically throughout the day. This is mainly due to people opening and shutting doors and windows, which draws fresh air in and flushes the radon containing air out. Superimposed upon these daily fluctuations is a seasonal variation which further complicates the picture. The levels in winter are generally higher because properties are heated more, so increasing the air pressure differential between the inside and outside. To overcome these hurdles, the NRPB recommends taking a measurement over a three month period, so that a meaningful average concentration can be established.

    A simple, postal test-kit10 is available from the NRPB, which costs approximately £36. It consists of two small plastic detectors, one of which should be placed in the main living area, and the other in the main bedroom. These detect and record the alpha radiation given off by radon in the air. After three months, the units are posted back to the NRPB, which analyses them and notifies the owner of the results.

    The NRPB has another, quicker service whereby you can obtain an estimate of the ‘radon potential’ of a particular property11 for a fee of about £18. Basically, this is a summary of the available results for other homes in the area and gives an idea of the probability that the property you are interested in will be above the Radon Action Level. It is not a substitute for measuring the actual level, however and probably only gives a similar level of guidance as the information tables in the Radon Atlas of England and Wales, which is freely available11.

    How to reduce radon levels

    If the radon level inside a property is too high, it can be reduced relatively easily. The Buildings Research Establishment advises on a range of possible methods which have proved very effective in reducing the amount of radon which seeps into a building12. One way is to seal the floor and joints with an airtight membrane to prevent ingress of the gas. Alternatively, a sump and fan can be installed under the floor to draw the radon out of the soil and feed it safely through exhaust pipes along the side of the house. Another method involves creating a positive internal air pressure by blowing air from the loft into the house. These solutions vary in price, the most expensive being the sump and fan which costs around £75013.

    The Radon Council, which is an independent regulatory body, has a list of approved contractors who are experienced in this type of work14.

    Dealing with the cost - Radon bonds

    To avoid stalling a transaction where the property is in a Radon Affected Area but the level has not been measured, the property lawyer could negotiate a radon bond13. This is a fair way to apportion the risk that remedial action will be needed between the buyer and the seller. The value of the bond should be roughly the cost of curing the problem, i.e. about £750 for a domestic property and this is deducted from the seller’s purchase price and kept aside until such time as the test proves clear. In the event that remedial action is required, the bond money is used to pay for the work. Once the level has been re-tested and found to be satisfactory, any excess money is returned to the seller.

    New buildings

    Since 1999, Building Regulations have required preventative measures to be installed in new buildings in those areas of England and Wales where the risk of the Radon Action Level being exceeded is highest. For example, sumps are created underneath the floor, to which fans can be attached later if the radon level proves to be too high inside the completed building. More information about the regulations and remedies is available from the Buildings Research Establishment15 and the Office of the Deputy Prime Minister16.

    Radon is an employer’s risk

    The question of whether a property is in a Radon Affected Area is not only relevant to residential conveyancing. The answer to enquiry 3.13 will be relevant to commercial sales and leases also, for example, where a company takes a lease of an office block or factory in which their employees will work.

    The Health and Safety at Work Etc Act (1974) imposes a duty on the employer to ensure the health and safety of its employees and other people who have access to the work environment17. Where the radon gas concentration is above 400 Bq m-3, the Ionising Radiations Regulations 199918 apply. These require the employer to take steps to reduce the exposure of its employees to radon. Where radon has come up as a potential problem in the report on title, the employer should arrange for a radon test to be done, unless the previous owner has done so. This measurement should form part of the employer’s risk assessment under the Management of Health and Safety at Work Regulations 199919.

    The employers’ action level (400 Bq m-3) is higher than the residential Radon Action Level (200 Bq m-3) because people usually spend more time at home than at work. Radon levels are likely to be low in well ventilated workshops and factories, but in more confined spaces, such as offices and shops, concentrations can build up.

    The same testing method used for homes should be used to measure the radon in commercial properties and this will take three months. Roughly one detector per 100 m2 of floor space is needed on the ground floor and in basements. The same remedial methods as for homes are also likely to be effective and the Buildings Research Establishment is a useful source of advice and guidance20.


    Care is needed in interpreting the answer to standard enquiry 3.13, because it does not give an actual measure of the radon level in a property. This is because the designation of Radon Affected Areas is based on an estimate by the NRPB of the likely percentage of properties with levels above 200 Bq m-3.

    The NRPB and the BRE provide useful information and guidance on how to deal with radon by installing remedial building measures.

    Employers have a duty to ensure that their employees’ health will not be damaged by a preventable problem.

    Although it is important, radon should not be a deal-breaking issue, because there are relatively inexpensive methods of remedying any problem and a radon bond can overcome the awkward timing issues introduced by the three month test.


    1. www.howstuffworks.com/radon1.htm
    2. Understanding Radiation, www.nrpb.org/understand/radon/radon.htm
    3. Cornwall Radon Gas Centre, Notes, www.cornwallradon.co.uk/page10.html
    4. National Cancer Institute, Questions and Answers about radon, http://cancerweb.ncl.ac.uk/cancernet.600352.html
    5. Department of Environment and Rural Affairs, About Radon, www.defra.gov.uk/environment/radioactivity/radon/about/
    6. http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebHome/Page/1153496333353?p=1153496333353

    7. Radon Atlas of England and Wales by BMR Green, JCH Miles, EJ Bradley, DM Rees, www.nrpb.org/publications/w_series_reports/2002/nrpb_w26.htm
    8. Guidance Notes, CON29 (Notes), available on Laserform
    9. Buildings Research Establishment, Radon Advice – Buying and Selling Homes in Radon Affected Areas, www.bre.co.uk/radon/homes.html
    10. www.nrpb.org
    11. Radon Survey, NRPB, Chilton, Didcot, Oxon, OX11 0RQ
    12. www.bre.org.uk/radon/reduce.html
    13. DETR leaflet Radon – Don’t live with the risk
    14. The Radon Council Ltd, PO Box 39, Shepperton, Middlesex, WD2 7JR
    15. BRE Report BR 211, www.bre.co.uk/radon/protect.html
    16. www.odpm.gov.uk
    17. HSE leaflet INDG210, Radon in the Workplace, www.hse.gov.uk/
    18. Ionising Radiations Regulations 1999, S.I. 1999/3232, Reg 3(1)
    19. Management of Health and Safety at Work Regulations 1999, S.I. 1999/3242
    20. www.bre.co.uk/radon/index.html

    Bullet Point Summary

    • Radon is important in domestic and commercial property conveyancing because it gets trapped inside buildings and high levels can cause lung cancer.

    • Property lawyers should ensure their clients are not buying a health risk unawares.

    • Commercial clients who are employers have a duty to protect their employees against radon in the workplace.

    • It is relatively straightforward and inexpensive to cure a radon problem.

Also published in Property Law Journal, 17 March 2003, Number 106