In response to comments from industry, the working group for BS8485 have updated and released the following which can now be ordered or downloaded from BSI. Please note that this is a technical reference, can be normative and the most current version should be that cited in reports.

BS 8485:2015+A1:2019 Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings describes how to characterise sites and prevent the entry of toxic, asphyxiating or explosive ground gases. This 2019 amendment changes and clarifies:

• The minimum gas protection points required for Buildings Type B, C and D on High and Very High gas hazard sites.
• The assignment of gas protection points for the structural barrier for basements.
• The criteria for membranes that can be assigned 2 gas protection points when used as a gas resistant membrane.
• The membrane thickness test method applicable to the guidance in the code of practice.

Other industry guidance exists but none provides the same clarity on remedial solution selection.

This standard also helps you comply with Building Regulations Approved Document C: Site preparation and resistance to contaminants and moisture.