Frequently asked questions
It is a naturally occurring radioactive gas which has no colour, smell or taste. Back
It comes from the minute amounts of uranium present in all earth materials such as rocks, soils, brick and concrete. Back
An increased lifetime risk of lung cancer. Back
Public Health England (PHE) recommends that radon levels should be reduced in homes where the average is more than 200 becquerels per cubic metre (Bq/m-3). This recommendation has been endorsed by the Government. Back
The Target Level of 100 Bq m-3 is the ideal outcome for remediation works in existing buildings and protective measures in new buildings. If the result of a radon assessment is between the Target and Action Levels, action to reduce the level should be seriously considered, especially if there is a smoker or ex-smoker in the home. Back
The main danger from high radon exposure is the increased risk of lung cancer. If there is any risk of leukaemia, it is, by comparison, extremely small. Back
PHE can provide advice and guidance on the health risks associated with radon. Back
Radon is present in all parts of the UK, but in the most populous areas the levels are quite low. Some of the highest levels have been found in the south west, but levels well above average have been found in some other parts of England and parts of Scotland, Wales and Northern Ireland. However, even in these areas most homes have low levels. Back
Yes. All countries are affected to some degree by radon, but the problem is receiving particular attention across Europe, USA and Canada. Back
The only way of establishing whether a house has a radon problem is by monitoring the house. Ask the seller whether the house has been tested. If it has been tested they should be able show you written evidence of the results, indicating whether it is above or below the recommended action level of 200Bq m-3. Back
You can have it tested. Unfortunately the most accurate method of measurement requires detectors to be in place for three months which is impractical for people buying houses. Short term tests carried out over 7-8 days can be used for screening purposes, but will probably need to be followed up later with a longer term test. The alternative is to test after moving in. In order not to lose out financially you may consider setting up a Radon Retention or Bond with the Vendor. For further advice on measurement contact PHE. Back
Go ahead with the purchase, the radon problem can be resolved after purchase much in the same way as other routine building problems such as rising damp or timber treatment. You should also familiarise yourself with the various radon remedial options and what they might cost. You may also consider discussing with the seller the possibility of a reduction in the purchase price, although the seller may have already taken this into account when pricing the property. Back
This is an agreement that is entered into by the buyer and the seller. It involves the buyer retaining a small part of the purchase price, that can be used towards paying for radon remedial works should they prove necessary after the house has changed hands. The money is usually held by a third party such as a solicitor, and after an agreed period of time any remaining money is returned to the seller. It maybe that radon monitoring shows that no remedial works are required in which case the whole sum is returned to the seller. Back
You need to agree how much money should be retained, over what period of time it should be retained and how the money maybe spent. Back
The amount of money retained needs to fairly reflect the remedial costs, that may be incurred by the purchaser, if the house is found to have an elevated radon level. For an average house £500-£2000 is typically the sum that is retained. This will cover most works that might be required, e.g. the current average cost of a sump system is £800 - £2000. Whilst it maybe desirable for the purchaser to see a larger sum retained it is unlikely that the seller will agree. They may have already taken radon into consideration in the valuation of their house. Back
This needs to be fair to both parties. As a minimum nine months is probably a fair duration. This would enable the house to be monitored for radon and have remedial measures installed. This allows five to six months from moving-in to receiving radon results, with a further three months to organise and carry out remedial works. It does not however allow time for any further monitoring or additional remedial works. Back
The important thing is not to let radon influence your choice of purchase, even in affected areas most houses have low radon levels, and where levels are high they can usually be reduced at reasonable cost. So, if you like the house for every other reason continue with the purchase, but do make enquiries to better understand radon. PHE can advise on average risk levels for the area you are moving to. You should also ask the seller whether the house has been tested for radon and request to see any results. If it has not been tested you should move in and have it tested. Advice on the different remedial measures is available elsewhere on this website. Back
While these terms may offer some indication of risk you should seek more detailed information on the risks for the area you are moving to from PHE. Back
It probably means that the house is located within an area where radon protective measures may have to be incorporated within new homes. If the house is brand new check with the builder to see what level of protection has been provided. If it is an existing house you should contact PHE to establish the likely radon risk in the area that you are moving to. Back
Requirements for providing radon protective measures were first introduced in parts of Devon and Cornwall in 1988 (interim guidance) and were amended in 1991, parts of Derbyshire, Northamptonshire, and Somerset were added in 1992. In 1999 the guidance was further revised to include areas throughout England and Wales. Back
It should mean that the house is located within an area where Full radon protective measures are required to be incorporated within new homes. Full radon protection comprises a radon barrier and provision for subsequent subfloor extraction or ventilation. The barrier is laid across the entire footprint of the building sealing the house from the ground below. This will usually provide adequate protection, but just in case a radon sump or ventilated underfloor void are also provided. By connecting a fan these can be used to further reduce radon levels. Back
It should mean that the house is located within an area where Basic radon protective measures are required to be incorporated within new homes. Basic radon protection comprises a radon barrier which is laid across the entire footprint of the building sealing the house from the ground below. Back
It should mean that the house is located within an area where secondary radon protection measures were required to be incorporated at the time it was built. Secondary protective measures involve providing a radon sump or ventilated underfloor void to enable for subfloor extraction or ventilation later. It means that if you find that your house has an elevated radon level you can connect a fan to reduce the level. Back
The only certain way is to ask if the house has been tested. If it has then the seller should be able to show you a copy of the results letter. If it has not you can obtain a report for the area in which the house is located from PHE. It will not reveal a result for your house but will provide an estimate of risk in the locality. Back
The important thing is not to let radon influence your choice of purchase, even in affected areas most houses have low radon levels, and where levels are high levels can usually be reduced at reasonable cost. PHE can advise on average risk levels for the area you are looking to moving to. You can also ask the seller whether the house has been tested for radon and request to see any results. Back
Radon has been an issue in a number of areas of the UK since the early 1980’s and there are no indications that it is making houses impossible to sell. Radon is simply seen as just another routine building matter like timber rot treatment or damp-proofing which are dealt with at the time of purchase. Back
Ask the builder to explain the level of protection that has been provided, and any action you should take after moving in. Back
Contact whoever is carrying out Building Control approvals. It is most likely to be local authority building control or the National Housebuilders Council, although other agencies maybe involved. The builder should be able to tell you who they are using. Back
The BGS site report is specifically designed to assist in determining the level of radon protection required in new dwellings. The PHE radon report service offers a more appropriate report for homebuyers. Back
To obtain the most accurate test results you really need to test over a period of several months. This is in order to eliminate any short term effects due to changes in weather conditions. Typically a three month test is recommended. Clearly this is impractical from the point of view of house sales. Short term tests over 7-8 days are available for screening purposes prior to purchase. They can then be followed up after purchase with a three month test. PHE can advise further on measurement protocols. The Radon Council Limited have members who can provide measurement services. Back
There is no direct evidence of increased risk to children, but in estimating the risk for the population, allowance is made for exposure in childhood. Back
Do solid concrete floors offer greater protection against radon than timber floors?
There is no clear answer to this, radon can enter a house through cracks and gaps in and around both concrete and timber floors. Whilst it might appear that a timber floor will be more leaky, they also have a ventilated void below to prevent timber rot, which can help to dilute radon.
I live in a radon affected area and the house I live in is built of local rock will this influence the radon level in my house?
The main source of radon is the ground below the home. Stone walls and fireplaces do not emit much radon.
My house has a stone fireplace is this the cause of my radon problem?
The main source of radon is the ground below the home, stone fireplaces do not emit much radon.
Where can I get information on radon protection for new buildings?
The current requirements and technical solutions are contained in BRE Report BR211 Radon: Guidance on Protective measures for new buildings. Back
Building Control have told me that I need a radon site report, where do I get one from?
A Radon Protection Measures geological assessment can be obtained from the British Geological Survey, Keyworth, Nottingham, BNG12 5GG. Telephone 0115 936 3143, or e-mail: firstname.lastname@example.org Other institutions such as universities may also be able to provide this information locally. Back
Building Control have told me I need to install basic radon protection what do I have to do?
You will need to provide a radon barrier across the footprint of the building. Back
Building Control have told me I need to install full radon protection what do I have to do?
You will need to provide a radon barrier across the footprint of the building and provision for future subfloor depressurisation or pressurisation by providing underfloor ventilation to suspended concrete floors or a radon sump. Back
What is a radon sump in a new building?
A radon sump is a small void, about the size of a bucket, constructed beneath a floor slab. Typically formed using bricks and a paving slab or a prefabricated sump unit the sump is linked to the outside of the building by a length of pipe which is then capped. If an elevated radon level is measured on completion of the building the cap can be removed and a fan attached to reduce radon levels. Back
Do I need to provide a fan and a sump during construction?
Only the sump needs to be installed during construction, it is up to the occupier to install the fan later if the house is found to have an elevated radon level. Back
I am upto first floor level with the brickwork and have now been told that I need to provide radon protection what can I do?
In-situ concrete floor : It is too late to provide a radon barrier within the concrete floor. However you could try to seal floor to wall joints with a gun-applied sealant prior to installing skirtings. This will not provide the protection of a full barrier but should help to reduce radon entry. You can also provide a sump. To confirm whether or not the sump needs to be activated the house should be tested on occupation.
Suspended beam and block concrete floor : A barrier could be laid across the floor and sealed to the walls with a gun-applied sealant prior to installing the floor topping. This will not provide the same effectiveness as a full barrier but should help to reduce radon entry. In addition make sure that the underfloor void is well ventilated. The house should be tested on occupation and if found to have an elevated radon level a fan installed to further ventilate the underfloor void. Back
I have nearly completed construction of a new house and now Building Control have told me that I need to provide radon protection.
It is too late to provide a radon barrier within the floor the only realistic option is to test the completed house on occupation. If an elevated radon level is found the builder should install appropriate remedial measures - probably either a sump system (with the sump excavated through the external wall from outside) , or increased ventilation to a subfloor void. Back
Do extensions have to incorporate radon protection?
The guidance contained within BRE Report BR211 Radon: Guidance on Protective measures for new buildings applies to all extensions to dwellings except where an exemption is provided in Schedule 2 of the Building Regulations. Back
Do I need to obtain a geological assessment for an extension?
There is little benefit to be gained by obtaining a geological assessment of sites in light grey squares in Annex B as the radon barrier is unlikely to cost more than the assessment. Back
Do I need to provide full radon protection in my extension?
The necessity of providing full radon protection (radon barrier and sump) is a matter of judgement for the Building Control Body. Large extensions that are designed to provide only ancillary accommodation may be re-arranged in the future to provide living accommodation. The size of the extension may be an indicator. If the extension is less than half the ground floor area of the existing house or 30m2, whichever is smaller, it could be considered to be relatively small. However, if the accommodation is designed as habitable space in the first instance radon protection should be provided at the appropriate level unless it is considered that full protection is not of significant benefit in which case dispensation under Regulation 8 could be considered. Back
Extensions with a ground floor area of more than half the ground floor area of the existing house or 30m2, whichever is the lesser, should have full radon protection if the house is in a dark grey square in Annex A or if a geological assessment indicates that full protection is advisable. Back
My extension is very small do I need to include full radon protection?
If the extension is only to be used as a porch, utility room or cloakroom/ shower room occupiers are unlikely to spend much time in these parts of their home. In these circumstances it may be possible to set aside full radon protection if it does not exceed the ground floor area criteria but this is a matter of judgement for the Building Control Body. In such a case there may be no need to obtain a geological assessment or to provide a sump, as it would be of marginal benefit when considered with the risk to the whole of the house. Back
How can I seal the joint between the new extension and original building?
One option is to cut a chase in the existing wall and then to tuck and seal the radon barrier into the chase. Whilst this is probably the best approach, other methods of joint sealing maybe be used e.g. bathroom sealant or other flexible filler. Back
If my house does not have a radon problem do I need to provide radon protection within the extension?
If a three month test result shows that radon levels in the home are well below the action level radon protective measures may be omitted from the extension. But if the result exceeds the recommended action level of 200 Bq/m3 appropriate protection measures should be installed within the extension and radon reduction measures provided in the existing part of the house. Back
The Building Control Officer has told me to provide radon protective measures in the barn that I am converting, what can I do?
If you are installing a new concrete ground floor you can install a radon barrier within the floor. Whilst the barrier will protect the bulk floor area radon could bypass the barrier and enter through the joint between the floor and wall. You could try to seal this joint using a gun-applied sealant. Even then radon might still enter via the old walls. As a consequence it is advisable to also provide a sump beneath the new floor so that If it proves necessary later a fan can be fitted to lower the radon level. Back
How does a sump system work?
A radon sump is essentially a hole in the ground with a fan connected to it sucking from the hole and thus producing a negative pressure in the hole. This negative pressure spreads through the pore spaces in the material immediately under the floor. The purpose of the radon sump is to reverse the air pressure between the soil and the dwelling and to stop the radon laden air from entering the dwelling. Due to their depressurising effect sump systems are sometimes referred to as sub-slab depressurisation systems. Back
How much does a sump system cost?
The PHE suggest the average price to be £800 - £2000. Actual costs will be dependent upon the construction and layout of the property. Back
Are sump systems noisy?
Inevitably there will be some sound from a fan powered sump system. But if care is taken in locating and installing a system it should not prove unacceptably noisy.Back
Do sump systems have to run continuously?
In most cases the fan will need to run continuously. There is limited experience of the effectiveness of running fans Intermittently, but it is known that frequent starting and stopping is more likely to result in premature fan failure. Trials have shown that radon can return to its original elevated level within a matter of a few hours of switching the fan off. Back
Do I have to have a fan on my sump system?
It is sometimes possible to use the natural stack or chimney effect of the building to drive a sump system and so avoid having to use a fan. This is called a passive sump system. To be effective it usually has to be located within the building with a vertical stack pipe routed up through the building and exhausting above the roof. Back
When can I use a passive sump system?
They are ideally suited to bungalows and have been used successfully with radon levels between 200 Bq/m3 - 3 Bq/m3. The important point is that if they fail to adequately reduce the radon level they can be upgraded by adding a fan. Back
Do all sump systems have to have a pipe up the outside of the house?
No, it maybe be possible, particularly with a bungalow, to route the pipework up the inside of the property. Alternatively if there are no doors, windows, or other openings such as vents adjacent to where the fan is located it can exhaust at ground level. Back
What is a condensate drain?
It is small device, fitted just above the fan in the stack pipe, used to drain moisture away from the fan. Back
Where can I get a fan for a sump system?
Most major manufacturers who market kitchen and bathroom extract fans can supply centrifugal in-line duct fans suitable for use on radon sump systems. Local builders merchants, electrical suppliers and some members of the Radon Council may stock suitable fans. Back
Can the fan blow into the sump?
In areas where the soil or fill beneath the building is highly permeable blowing can work better than sucking. Usually fans are installed in suction and only reversed to blow if suction fails to reduce the radon level. Back
Where can I get more information on radon sump systems?
Further information is contained in BRE Good Building Guide GRG 37 Part 3 Radon solutions in homes: radon sump systems. Back
How can I increase the underfloor ventilation in my home?
You can increase the natural underfloor ventilation by providing additional underfloor vents, or replacing old terracotta vents with new louvred plastic vents. This can prove effective and has been used with levels upto 700 Bq/m3. Higher radon levels can be dealt with by increasing ventilation using a fan. If the levels are very high - 1000 Bq/m3 or more or the property is large you may need to use more than one fan. Back
Where can I get more information on increasing underfloor ventilation?
Further information is contained in BRE Good Building Guide GRG 37 Part 1 Radon solutions in homes: improving underfloor ventilation. Back
How does positive pressurisation work?
Positive pressurisation works by taking air from the loft space, or from outside, and blowing it into the house. This creates a very slight pressure which can be just enough to counter the natural stack or chimney effect which draws radon into the house from the soil. At the same time the additional air being blown into the house has a diluting effect on the radon. Back
How effective are positive pressurisation systems?
They are generally effective only at moderate radon levels, up to about 700 Bq/m3, and work best in more airtight dwellings. Back
How much do positive pressurisation systems cost?
The units themselves range between £350 and £750. There will be an additional cost for installation, but they are relatively easy to install so can be carried out on a DIY basis. Back
How much do positive pressurisation systems cost to run?
The latest systems are advertised as costing no more than a couple of pence per day to operate. Back
Do positive pressurisation systems offer any benefits other than radon reduction?
Yes. They are widely used to reduce condensation in homes. They can be used to resolve both a radon and condensation problem in a house. Back
Are positive pressurisation systems noisy?
Inevitably they will generate some noise, but when sited away from noise sensitive locations and appropriately mounted they should not prove unacceptably noisy. Back
Where can I find more information on positive pressurisation systems?
Further information is contained in BRE Good Building Guide GRG 37 Part 2 Radon solutions in homes: Positive house ventilation. Back
How effective is sealing cracks in floors and walls?
Generally, it is difficult to reduce the radon level to much less than half by this means. It is likely to be effective only at moderate radon levels, upto 400 Bq/m3. Sealing is usually only recommended where there are obvious large openings through the floor i.e. bits of floor boarding missing, large openings around service pipes, or large cracks around concrete floors. It is difficult to ensure that you have successfully sealed all gaps and cracks. Back
How can I seal a suspended timber floor?
Complete sealing of timber floors e.g. with a continuous polyethylene sheet, is not recommended, as it may cause excessive moisture movement or induce timber rot, although sealing of large holes or covering a poor timber floor with hardboard is however an appropriate method of tightening a timber floor. Back
Would sealing the walls and floors in my cellar be effective?
Major sealing work to walls and floors in cellars and basements is usually only a viable option where it forms part of work being carried out to convert an unused space into occupied space, e.g. where walls and floors are being tanked to prevent moisture entry. Back
Where can I get more information on sealing cracks and gaps in floors?
Further information is contained in BRE Report BR239: Sealing cracks in solid floors: a BRE guide to radon remedial measures in existing dwellings. Back
Will opening windows more often reduce radon levels?
Simply opening windows is unlikely to have a significant long term effect, in fact in some cases opening windows can actually increase radon levels. Back
Is it possible to change the way in which I ventilate my house to reduce the radon level?
It may be possible to change the way in which you ventilate your home to help avoid drawing radon up through the floor or walls of the house. However as this depends on the way in which you live in the house it is not generally a reliable method. It may be suitable for radon levels just above the action level. Back
How can I change the way I ventilate my house to reduce radon levels?
Typical examples of appropriate measures include installing trickle ventilators to windows, particularly downstairs, capping off and sealing unused chimneys, draught stripping loft hatches and avoiding use of open fires and solid-fuel-effect open fires. Back
Is it worthwhile trying to increase the ventilation to my cellar?
Improved natural or mechanical ventilation targeted on the cellar or basement, where the highest radon levels are likely to be, can prove extremely effective, and offer large radon reductions. Back
Should fans used to ventilate cellars extract air out or blow fresh air in?
There is no clear answer, both have been found to be effective in reducing radon levels to the rest of the building. However it is important to note that a fan extracting air from a cellar will increase the radon level within the cellar itself even though it may reduce levels in the house above. As a consequence if the cellar is likely to be used on a regular basis we would recommend blowing air into the cellar, or to use an alternative solution such as a sump system. Back
Where can I get more advice on reducing radon levels in a house with a cellar?
Further advice is contained in BRE Report BR343: Dwellings with cellars and basements: a BRE guide to radon remedial measures in existing dwellings. Back
Can ionisers, electrostatic precipitators or air cleaners be used to reduce radon levels?
None of these devices are very effective when compared with other solutions. Back
Where can I obtain maps showing the areas of the country affected by radon?
Indicative radon risk maps can be down loaded from the ukradon.org website.
Where can I find maps to determine whether or not I need to provide radon protective measures within a new house?
Maps are contained within BRE Report BR211 Radon: Guidance on Protective measures for new buildings available from the BRE Bookshop.
Where can I obtain maps showing radon risk based upon geological risk assessment?
British Geological Survey, Keyworth, Nottingham, BNG12 5GG. Telephone 0115 936 3143 , or e-mail: email@example.com
How long do I need to test for?
In order to eliminate any short term effects caused by changes in weather conditions it is recommended that you should test over a period of several months. Typically a three month test is recommended. Short term tests over 7-8 days are available for screening purposes for checking radon levels after installation of remedial measures or for checking properties prior to purchase. It is usually advisable to confirm short term results with a long term test. Instantaneous measurement equipment is available but results require expert analysis and is really only of use to specialist contractors. PHE can advise further on measurement protocols
Who do I contact in order to have my house tested for radon?
PHE offer measurement services and can provide an up to date list of validated laboratories. A further list of companies providing measurement services can also be obtained from The Radon Council Limited.
Am I exposed to radon at work?
Radon concentrations in workplace buildings can also reach quite high levels. You should discuss the matter with your employer and ask them to contact the Health and Safety Executive (HSE) , Local Authority Environmental Health Department or PHE for advice on the need for measurements.
I am an employer. Do I need to measure the exposure of my employees?
The Ionising Radiations Regulations 1999 impose a duty on employers to protect workers from exposure to radon. You should contact the local HSE area office or the Environmental Health Department of your local council (whichever you normally deal with for health and safety matters) for advice on whether the regulations are likely to affect your business. Further guidance is available in BRE Trust Report FB 41 Radon in the workplace.