In June 2015, BSI, the Business Standards Company, revised (and renamed) BS 8485 “Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings”.
The standard is a key piece of guidance for design consultants to give recommendation and describe methods for the investigation of ground gases like methane and carbon dioxide during development of affected sites, and regulators (environmental health officers and building control) who need to assess/approve foundation designs.
The original document; BS8485:2007 was brought up-to-date in the new version: BS8485:2015. The thinking behind this was that the original standard didn’t go far enough in regards to the specification of the gas membrane itself and the British Standards Institute wanted to enforce more stringent permeability levels, especially where methane gas is concerned. This is in order to increase resistance to methane gas permeation through the membrane.
Key changes to BS 8485:
- Clearer guidance on the interpretation of gas monitoring data and assignment of gas screening values
- Reference Technical Note RB17 characteristic situations classification using TOC (toxic organic compounds)
- Review and expanded guidance on protection measures scoring (old Table 3)
- Include reporting requirements of gas protecting measures
- Added informative guidance in annexes on radon and volatile organic compounds (VOC’s)
- More detailed guidance on interpretation of gas monitoring data
- Recommendations on membrane selection and verification
Phil Bull, Commercial Director at Visqueen Building Products said:
“It is vitally important that the industry recognises that BS8485: 2007 has gone and is no longer valid unless the contractor using the products had a planning condition in place prior to June 2015. Here at Visqueen we are adapting our existing gas barriers and membranes to ensure full compliancy required by BS8485:2015. It should be a priority for every relevant manufacturer to start the process of adhering to the latest version of the standard.”
These changes have and will pose a great problem for a number of UK membrane manufacturers due to the fact that there aren’t that many within the UK that are equipped to produce single wound membrane in line with the new recommendations, so this aspect of the latest criteria may pose problems for some manufacturers in becoming compliant.
Whilst the industry is beginning to adopt the new version of the standard and it is getting better overall, there is still a lot of ambiguity surrounding this and lot of our competitors (manufacturers) are stating openly that their products are BS8485 compliant but upon closer inspection, the products are BS8485: 2007 compliant which is now null and void.
These organisations are hiding behind the statement until they are asked the question. When asked the question, they are backing away and eventually having to come clean that their products are, in fact, non-compliant. Visqueen Building Products have not seen any of their competitors talking about their products being BS8485:2015 compliant for instance.
The BBA (British Board of Agrément), is committed to helping businesses and organisations supply the construction industry with products, systems and installers of the highest quality. They have therefore now suspended certs which cannot prove compliance to BS8485:2015.
The BBA recognise that the newly improved Visqueen Gas Barrier meet the criterial of the minimum 370 g/m2 and 40 mls/m2/d.
Following the BBA recognition, Visqueen Building Products are now working towards adapting their existing Gas Barriers and gas membrane products to bring it up to full compliance with current industry requirements documented in BS8485: 2015.
The new range of additional products will shortly be available to the industry. Please note that BS8485 does not give guidance to ground gases other than methane and carbon dioxide. The guidance on the use of synthetic geomembranes as barriers to volatile organic compounds are referenced in annex in BS8485, which will be communicated in a different bulletin.