Radon testing for basements

Radon testing for basements

Radon testing in basement conversions

Radon Gas

All basement waterproofing work is subject to guidance given in BS 8102. The standard requires all waterproofing designers to take account of the risk of ‘Ground Gasses’, which over time could penetrate into a basement and present a health risk to occupants.

Radon is one of the naturally occurring ground gasses and is present in some quantities everywhere. It is a radioactive gas which is both colourless and odourless and comes from radioactive decay of radium deep under the earth. Radon has only been measured to any extent for around 50 years, but epidemiological studies provide strong evidence of association between exposure to indoor radon and lung cancer.

Radon gas can seep into enclosed spaces (e.g. Buildings), collect and build up; the levels reached are dependent upon atmospheric conditions, the structure of the building, local geology and ventilation. Basements are particularly susceptible to large accumulations, as there is a greater area in contact with the soil and radon tends to be heavier than air and will ‘pool’ in basements, rather like water will collect in a sump.

Due to the underlying geology and varying amounts of uranium present in the ground, properties in certain areas of the UK are more likely to contain high levels of radon gas. Although some properties are situated in a “non-affected” area it could still be affected with high levels of radon gas. Similarly, some properties in “affected areas” may not be affected by radon at all. Radon maps were not designed with basements in mind, so they cannot be used to reliably identify radon levels in individual properties.

In preparing our initial waterproofing specification, an assumption is made that radon levels are at or below the currently specified ‘safe’ level. However, in the light of the above, the best and safest way of determining this is to carry out radon testing.

This takes some time because radon levels fluctuate through days or weeks so we cannot say whether we initially need to specify extra protection to keep levels down.

All our client can decide to have testing carried out in advance of commencing their basement waterproofing project, so our specification can take account of the radon levels (if they are high), or you can ask for an enhanced waterproofing specification to keep radon down anyway (though the cost may be wasteful if levels are low), or you can commence without any radon testing, provided you are comfortable with the potential risks. Where radon is concerned you are in charge of any decisions, but we believe that you should be able to face these choices with good, accurate information.

Testing over periods of less than three months may not be completely accurate because radon penetration can ebb and flow over long periods. If this delay is not a problem then a three month test is recommended. However, meaningful testing can be done over 30 days. We do not recommend testing at shorter periods but subject to your instruction – 10 and 7 days periods can be offered as a guide only.

A written report is then produced with advice on what if any, action should be considered. This is an important document because even if radon levels are low, a written report confirming this will give you confidence that your family are not at risk spending time in the basement (this is especially important if bedrooms are included). In addition, the radon issue is growing in importance and the media are now reporting on it; if you wish to sell the property or raise finance on it in the future, a ‘clear’ radon status or a radon proofed basement system will be desirable.


For further information on Radon testing for basements, please contact us.