Myth busters for ground gas protection membranes

Myth busters for ground gas protection membranes

To combat the issues of harmful ground gases dissipating into buildings constructed on contaminated land, gas protection membranes and accessories are essential as required by Building Regulations and British standards.

Information available insists certain aspects of a gas protection membrane should have particular performance criteria to comply. In fact, when following the regulations, it becomes clear what is necessary. The list below describes how Protect GDB10 Plus by Glidevale is compliant.

The methane gas transmission rate for sheet and joints is required!

Many membrane manufacturers state the methane permeability rate for the sheet of the membrane, omitting one of the most at risk areas, the lapped joints. Protect GDB10 Plus is one of the only products on the market that has been independently methane permeability tested to BS ISO 15105-1 for joints. This provides peace of mind to contractors and housebuilders that the product will create a fully sealed system.

  • GDB10 Plus exceeds the requirement of <40ml/m²/Day @ 1atm for Methane transmission at <0.3ml/m²/Day @1atm for sheet membrane, and 3.56ml/m²/Day @ 1atm for 150mm taped joints.


BS 8485 Table 7 – welding isn’t always a requirement!

Table 7 gives the performance criteria for the gas resistant membrane. It describes the methane transmission rate, how it should be durable enough to withstand the life of the building, the in-service stress and the installation process. It should also provide a complete barrier to the entry of relevant gas.

The criteria stated does not reference welding of the membrane. Furthermore, BS 8485 and CIRIA C735 goes on to say it can be joined using welding techniques or tapes!

  • GDB10 Plus complies with BS 8485 Table 7 whilst providing a simpler fixing solution to save time on site. Only one 150mm wide gas resistant tape is required at laps.

Thickness of a membrane does not indicate performance of a membrane 

BS 8485 and CIRIA C735 states that thickness is only a key parameter should the membrane need welding. Thickness of a membrane is dependent on the type of materials used to produce the membrane, a direct link cannot be made between thickness and performance.

  • Being a thinner membrane, and having a low mass of 195g/m², GDB10 Plus gives the advantage of an easier installation through effortless handling on site and folding at corners. It also has excellent puncture resistance and tensile strength.


Glidevale also supplies a range of purpose designed, pre-formed accessories to maintain protection at wall cavities, corners, and services to remove the need to form difficult shapes on site. A range of underfloor and cavity wall ventilation accessories removes gases and moisture vapour where required, enabling regulatory requirements for ventilation to be met.

Click here to download the full Ground Floor Protection brochure

Click here to download the BM Trada certification for GDB10 Plus

Contact 0161 905 5700 or email for a free quotation or further technical advice.