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What Is A Gas Membrane?

As awareness increases and we are becoming more knowledgeable the extent of ground gases developing into a problem grows across the UK. The potential negative impact of ground gases is consistently becoming more evident by specialists, contractors and homeowners.

If ground gases are present while building it is required that the chance of these gases entering a property is reduced while complying to building regulations. The most common option to achieve this is through the installation of a ground gas membrane or ground gas protection system.

Usually installed as part of a building’s foundation, a gas membrane is a plastic sheet that prevents ground gases from permeating upwards. Gas membranes, in many cases, also act as a damp proof membrane halting moisture ingress from the ground.

Why Is A Gas Membrane Required?

Gas membranes are required on all high risk sites with the level of risk determined by a ground gas report. Gas protection systems are critical in developments constructed on sites affected by permanent ground gas and/or volatile compounds (VOC) contamination.  

Depending on the specific permanent ground gas or VOC risks associated with the site current legislation stipulates certain levels of protection. Ground gas can enter structures through gaps and service pipes, construction joints, wall cavities and cracks in walls and ground slabs.

What Are The Types Of Ground Gases?

Ground gas usually refers to carbon dioxide and methane. Both of these gases are produced through micro-organisms breaking down organic material. Landfill sites are often the cause of methane and carbon dioxide, but they can occur through backfill, wetlands or soils with a high organic content, inert fills and soil gas. Ground gases can also occur naturally through coal bearing strata, bedrock containing uranium, limestone and organic sediments.

There are many different types of ground gases beyond methane and carbon dioxide. These include:


Radon is a radioactive gas, we can’t see, smell or taste. Guidance on protective measures for new buildings. (RADON) BRE 211:2015

Carbon Dioxide

One of two most common ground gases found in the UK typically found near landfill sites, but can occur from other sources.

Carbon Monoxide

Commonly associated with both natural and anthropogenic gas sources. CO can be odorous, toxic, asphyxiating, flammable and explosive.


Often found near landfill sites, protection against methane needs to follow BS 8485:2015+A1:2019 codes of practice.

Hydrogen Sulphide

H2S is a very toxic, flammable gas. It is pungent (rotten egg odour) and irritates the eyes, nose and throat.

Volatile Organic Compounds (VOC)

Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. Assessment and management of risks associated with Volatile Organic Compounds (VOCs) is required.

How does ground gas become a problem?

Both brownfield and greenfield sites have the potential to develop ground gas from naturally occurring or man-made sources. These gases have the potential to build-up leading to property damage and serious health implications. A build-up of methane can lead to methane and carbon dioxide can result in suffocation. 

Even in small doses ground gases can be harmful and there have been many reported deaths due to ground gas ingress in homes.

How can i protect against ground gas?

All parties working in the construction industry need to consider the hazards of ground gases when designing and constructing new developments. Potentially very dangerous ground gases can enter buildings after construction is complete if correct measures aren’t put into place. 

This is where a ground gas protection membrane is required as it omits gas from flowing from the ground into a building. Membranes are lightweight, flexible and formable due to their structure being made from polymers. There are multiple options through which a ground gas specialist can protect against harmful gases. Whichever method is chosen, however, the installation must be approved by an independent gas specialist as outlined in CIRIA C735 ‘Good practice on the testing and verification of protection systems for buildings against hazardous ground gases’.

How to find a ground gas specialist?

Ground gas membranes are required to ensure that harmful gases can’t penetrate the building and are vital for the safety of you and anyone else who uses your building. This is why it is equally as important to source the right ground gas specialist and gas membrane engineers for your project. 

APP Protect works with the very best suppliers and manufacturers of ground gas protection systems. We have delivered installations across many projects with varying levels of contamination in Cambridgeshire. Our expert team of surveyors are always available to support our design team to establish a robust specification suitable design for ground gas protection. 

For over 50 years we have delivered affordable ground gas membranes and have built our reputation through quality, trust and loyalty with our customers.

We’re Ready To Help You

Please get in touch with our friendly team today and we can get the ball rolling on your project sooner than you think.

01223 244 515