Ground Gas/Radon Mitigation in Basements

Where existing basements occur in areas at risk of Radon, then suitable measures need to be taken to reduce the amount of Radon entering the property through the basement. BRE Guidance 343 – Guide to Remedial Measures in Existing Dwellings, identifies the following methods of reducing the amount of radon entering the basement:

  • Sealing floors and walls
  • Increasing underfloor ventilation
  • Improving ventilation to the basement area
  • Installing a Radon Sump
  • Introducing positive pressure ventilation to the property
  • Improving ventilation to the property

In areas where Radon levels are considerably low, then an appropriately installed waterproofing system would generally suffice. However, in areas with high Radon levels, then the installation of a cavity drain system along with a Radon Sump and/or Positive Pressure Fan would be appropriate. It is always recommended to monitor the basement Radon levels after installation to ensure the installed measures are more than adequate. Radon test kits are available.

For new build Radon protection in a basement, BRE211 states;
“If a basement cellar is to be tanked with an impervious barrier to prevent damp penetration, the tanking will also provide Radon protection. There is no need to provide supplementary protection (e.g. a sump) in such cases.”
In essence, if an external tanking system is recognised by the BRE, then it also qualifies as a Radon barrier.

atal Products Used…

atal Radbar 300

atal Radbar 500

atal Bentofix 5300

atal Liquid Gas Barrier

atal Premsil GMA

If you are building in an area with elevated radon potential, you must install radon protection. Although the precise areas where measures should be taken are listed in the BRE Guidelines (BRE 211 Radon: Guidance on Protective Measures for New Dwellings), these are reviewed by local government in the light of advice from the National Radiological Protection Board and the British Geological Survey.

It is recommended that current information on the affected areas should be obtained from local authority building control officers or from approved inspectors.
Note: Radon protection now applies to extensions and any change of use to a residential or sleeping use.

When choosing an appropriate Radon barrier, levels should be assessed. It also needs to be decided what level of protection is required, whether it be a basic, passive vented system or in exceptional circumstances a mechanical system may be required.
atal can aid the decision-making process and advise on appropriate materials to achieve the specification in accordance with BRE 211 recommendations.

CO2 & Methane

Both Methane and Carbon dioxide are odourless and colourless, and it is only the presence of trace gases that produces the distinctive landfill gas odour. There are many hundreds of types of trace gases, but most do not usually represent a health hazard following normal atmospheric dilution.

Ground gas is mainly composed of Methane and Carbon Dioxide (C02) and presents similar risks to that of landfill gas. Ground gas can be formed by natural or man-made means. The following are common sources and their typical components:

  • Peat bogs and mosslands
  • Carbonate rocks such as limestone and chalk
  • Organic rich rocks such as coal measures
  • River and lake sediments
  • Made ground
  • Farmland
  • Sewers

Precautions need to be taken for Methane as it may give rise to a variety of hazards if it migrates to and accumulates in a property or confined spaces. If generated in sufficient quantity, the gas may form an explosive mixture with air. It can also act as an asphyxiant and in certain circumstances, it may be toxic. Carbon dioxide is also an asphyxiating gas and causes adverse health effects, unconsciousness or even death at relatively low concentrations. The nationally recognised guidelines to protect structures from ground gas in the UK is BS 8485:2015.

At atal we have ground  gas protection systems that are suitable  all applications as required to comply with BS8485: 2015. Protection for Methane and Co2 is the same, essentially materials need to be BBA certified to comply with NHBC, if not robust independent tests by the manufacturer are generally accepted.

atal Products Used…

atal GP1 gas barrier

atal Bentofix 5300

atal Liquid gas barrier

atal Premsil GMA


Hydrocarbon membranes should be specified on a site by site basis. For a recommendation tailored to your specific needs, send your ground gas investigation report along with construction details to our technical department. 

Please contact us to arrange a meeting to discuss your specific requirements at your convenience. atal UK are able to aid design, supply and installation, a quotation can be arranged if required.

If you need help or advice regarding Ground Gas Protection options for your project or property, please contact us on 01495 717202, or alternatively you can contact us online and one of our team will get back to you.


The customers that have been supplied with the admixture have been pleased and we have had no issues with strength or quality.

The change to the bags sizes(introduction of the water soluable bag) has made it easier especially for manually handling on the plant side.

- Kevin D'Souza - London Concrete

The atal service has been fantastic, the architect specified the types of waterproofing that we’d need. We had early design meetings with atal and the main contractor and from that point we’ve gone through the whole process from design to copmletion. They’ve been great.

- Simon Mann

Thankyou so much to atal for inviting me to todays meeting. I've learnt a whole lot about building physics, Type B Waterproofing and seen some really interesting case studies. The product looks absolutely fantastic and will do very well i'm sure of it!

- Adam Meyrick

I have worked with the guys at Atal for a number of years now whilst working for a number of companies & I would recommend them to other potential customers. I like their proactive approach, customer service, technical knowledge & speedy deliveries. 


If I ever have a problem or detail that needs resolving there is normally  someone available to help, even if it means them jumping in the car & visiting one of our sites at short notice!

- Richard Cleghorn MCIOB, P Chapman Construction

Great service on pricing enquiries for supply and Install, also repairing work - friendly and efficient staff.

- Simon Marsh

I would go with atal for waterproofing on any of my projects!

- Mike Mansfield, Intelle Construction

MJL Contractors Ltd have worked with Atal for a number of years now. We appreciate the professional & approachable manner offered by all of the staff at Atal & we know that if we have a problem we only have to pick up the phone & they will do their best to solve it. Prices are competitive & deliveries arrive as agreed.

- Richard Cleghorn MCIOB, MJL Group Limited

‘’Project architects, RDA liaised with Atal to bring forward a set of waterproofing and tanking details to ensure a water tight lower ground floor level within the setting of the original Bristol Evening Post print factory basement.  Atal provided us with design drawings and specifications founded on their product range and comprehensive industry experience, with which we were able to confidently develop our working drawing package.’’

- Rich Brown – Russ Drage Architects

‘’We had the fortune of being introduced to Atal via our main contractor. We were very pleased with the work they carried out. Although we had some challenges with some leaks with our new build Atal was able to identify the source of the problem very quickly and resolve it immediately. I would have no hesitation in recommending Atal.’’

- Prakash Patel – Hertz

‘’We have completed the groundworks package and almost completed the RC frame package at ‘’3 Glass Wharf’’ in Bristol on behalf of HMRC through Wates Construction. Throughout this project 4D Structures worked alongside Atal UK to ensure the waterproofing elements involved were installed to the highest standard. It was a pleasure working with Atal from design stage right through to the final sign off. They provide a brilliant service from design, supply of materials and also on site help and pre pour inspections. I would highly recommend them and look forward to working with them again in the near future.’

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‘’Atal have provided consistently quality products, on time at very competitive prices when compared to other high spec structural waterproofing brands. Customer Service has also been consistently, and the inclusion of detailed design documents tailored to specific projects goes above and beyond what other waterproofing companies are often willing to do. Overall, Atal have provided reliable, high quality products and customer service every time we have required their expertise’’ 

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"Atal have a comprehensive product range, they always offer practical achievable solution and delivery on time results. David is very knowledgeable, and his positive approach is refreshing, hopefully we will continue to enjoy our mutually beneficial relationship, long into the future.”

- Simon Monk - McDermotts

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