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Contaminated Land – Dual Construction Standards

Author/Issuer: Cavitytraystandards    Added:

Contaminated Land

Dual Construction Standards

Yeovil-based Cavity Trays Ltd reports an increase in the protection of new homes against radon gas, the naturally occurring gas that Government figures advise is responsible for an estimated 2000 avoidable deaths in the UK every year. Cavity Trays manufactures a range of radon arrestment products and suggests the growing activity is as a result of announcements made by the World Health Organisation and UK Government.

The World Health Organisation announced that radon is more dangerous than first realised.

It qualified there is no such thing as naturally occurring indoor radon as it only occurs naturally out of doors. Radon occurring indoors is the responsibility of those who put the building on the land.

This was followed by an announcement from the Health Protection Agency (HPA)  – recently renamed Public Health England – advising the Action Level for radon gas of 200 Becquerels still applies when constructing a dwelling, but suggests construction is preferably to a safer level called a Target Level of 100 Becquerels.

Thus dual standards exist.

These dual standards place the architect and builder in an unenviable position:

To what extent do they have a duty of care to build to the safer standard given the government announcement?

Could a subsequent liability claim be made by a client if an identified health risk is ignored?

Currently architect and builder place reliance on maps indicating where locations are radon affected. They can then make appropriate decisions regarding radon protection measures. Safeguards to arrest radon gas from entering the building envelope are easily introduced into a build programme. The use of a radon-resistant oversite membrane linked to radon cavity barriers in the exterior walls establishes building footprint protection. Radon gas discharge outlets in the masonry skin of the exterior walls below barrier level provide radon evacuation routes. Sumps are also available to exploit pressure differentials above and below ground.

Importantly it should be borne in mind that radon maps are not based on radon emissions from the ground. They actually denote whether existing properties in an area when tested had elevated radon levels. Given that existing properties will be predominately less airtight than those being built to today’s new standards, suggests reliance on a new property being able to naturally disperse radon to the same extent is unwise?  It should not be assumed readings taken within a newly built property will be similar to those within an adjacent older property.

One of the main entry routes of radon into a property is via the ground floor slab / inside leaf junction. A more airtight property might feature the same radon entry opportunities but not the exit opportunities, raising the question of whether radon concentrations could accumulate within the property? Measures should be taken when constructing in anticipation of this – rather than discovering when tested upon completion that the building falls outside of the regulation radon limit.

A spokesperson for Cavity Trays commented:  ‘We advise enquirers seek clarity from their local authority and their insurer regarding to what extent a property incorporates safeguard measures and their liability position given the dual Becquerel levels announced. The eventual decision making is often a personal one by the property customer  – influenced by the reduced health risk to their family and the likelihood of the property having more appeal and asset value in the future should they sell. And of course, in the event of the Action or Target Levels being lowered one day, a protected property is likely to be a more attractive asset when compared with alternatives’.

For more information about radon, radon arrestment products and how to protect buildings using preformed radon barriers and accessories, contact the Yeovil Helpdesk.

Suggested reading available from Cavity trays Limited ‘Protecting the Building Envelope’ issue 22.


Radon Barriers for use within cavity walls
Radon Barriers for use within cavity walls


When new properties are constructed there is a regulation requirement to ensure the building (and thus its inhabitants) are protected against the effects of radon gas. The problem is how does one know whether or not a building is affected? The answer is surprising. The only way to determine whether a building is affected is to test it – and that is only possible after the building has been completed. Hence the move to incorporate measures when building from new as so doing removes chance and speculation.


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