Can Anyone Install Gas Barrier Membranes Correctly?

Starting a building or renovation project involves countless details, and it can feel overwhelming at first. One crucial consideration is often overlooked: dangerous ground gases can find their way into your home. These gases pose serious health risks and must be addressed early in the process. Ignoring them can lead to costly and hazardous consequences later on. To prevent harmful gases such as radon and carbon dioxide from entering, experts install gas barrier membranes or barriers beneath your home’s foundations. These protective layers block the movement of gases and help ensure that the indoor air remains safe. Installing them correctly is key to long-term protection. It’s a proactive investment in both health and structural safety.

In this blog, we explore the importance of gas barrier membranes and how they shield your home from hidden threats. You’ll learn when a gas barrier is necessary and how these thin but powerful materials work. A proper understanding can help you select the right professionals and materials for the job.

Understanding Gas Barrier Membranes

What Are Gas Barrier Membranes and Why They are Essential

Gas barrier membranes are durable plastic sheets positioned beneath a property’s foundations to prevent harmful ground gases from entering. These sheets form part of the early construction process and must be installed correctly to ensure full effectiveness. They create a sealed layer that blocks gases such as methane, radon, and carbon dioxide. Builders typically install them before laying concrete slabs or flooring.

Ground gases travel through soil particles and can seep into a property through gaps in the foundations. Once inside, these gases can accumulate and pose serious health risks to occupants. Symptoms of exposure may include headaches, nausea, and long-term respiratory issues. Membranes mitigate these risks by intercepting gases at their source.

Gas barrier membranes are particularly vital in high-risk sites or areas with elevated radon levels, which are widespread across the UK. Radon is a naturally occurring radioactive gas that has been linked to lung cancer. Local surveys or site assessments usually determine whether a gas barrier is required. Builders must adhere to strict regulations to ensure compliance and maintain the safety of the property.

Situations That Necessitate the Use of Gas Membranes

Modern construction regulations require the use of gas barrier membranes for projects located in high-risk gas areas, as defined by official geological data. These regulations are informed by specialist reports and mapping provided by the British Geological Survey.

Builders must carry out thorough land assessments during the planning stage to identify any potential gas hazards. Failure to comply can lead to serious legal and safety consequences.

If your site falls within a high radon or general ground gas risk zone, the installation of a gas membrane is mandatory. This membrane acts as a physical barrier, preventing gases from seeping into the building. For the membrane to be effective, it must be laid with precision and remain free from damage. Building inspectors often examine the quality and placement of the membrane before granting final approvals.

Gas membranes are particularly important in areas with a history of industrial activity, former landfill sites, or natural geological conditions that emit gases. Even rural locations can fall within high-risk zones due to certain underlying rock formations. Understanding the gas classification of your site enables you to incorporate necessary safety measures from the outset. Early identification not only enhances safety but can also help reduce costs and ensure long-term protection for future occupants.

What Do Gas Barrier Membranes Actually Protect Against?

Understanding Ground Gases

Ground gases exist within the tiny pore spaces between soil particles and can migrate upwards into homes and buildings. These gases include radon, methane, carbon dioxide, and carbon monoxide. In significant quantities, they can reduce oxygen levels and pose serious health risks, such as dizziness, unconsciousness, or even suffocation. They typically infiltrate properties through foundation gaps, service ducts, or inadequately sealed floors. Continuous monitoring is crucial in high-risk areas to detect their presence at an early stage.

These gases originate from both natural decay and human activity, including industrial processes and poorly managed waste. Former mines, landfill sites, and contaminated ground are common sources, often trapping and slowly releasing gases over time. Additionally, the decomposition of organic matter contributes to underground methane and carbon dioxide levels. Without proper mitigation, these gases can travel substantial distances through the soil. Construction projects near such sites require enhanced protective systems to control and reduce emissions.

While small amounts of ground gases are generally not hazardous, long-term exposure can pose significant risks to both health and property. Prolonged contact with radon has been strongly associated with an increased risk of lung cancer. Methane, due to its high flammability, presents a major explosion risk in enclosed environments. Carbon monoxide, though odourless and invisible, can be fatal in confined spaces. Addressing these dangers early in the planning and construction stages helps avoid costly remediation and safeguards future occupants.

Assessing the Safety of Gas Membranes

When correctly installed, gas membranes provide a dependable defence against harmful gases seeping into your property from the ground. They offer peace of mind by preventing substances such as radon and methane from infiltrating indoor spaces. These membranes help preserve indoor air quality and reduce the risk of long-term health issues. In addition, a properly applied membrane enhances the value and durability of the property.

To ensure safety and compliance, it is essential to verify that the membrane being used is BBA-approved, confirming its quality and suitability for purpose. The British Board of Agrément (BBA) approval indicates that the product has undergone rigorous testing and meets stringent performance standards. It also confirms the membrane’s durability and effectiveness under real-world conditions. You should request proof of certification from your contractor before any installation work commences.

Contractors who use certified materials should be transparent about the products they install and their respective performance ratings. A responsible installer will clearly explain how the membrane functions and why it has been selected for the project. BBA-approved membranes provide assurance that your building complies with regulatory safety standards. This certification is not merely a recommendation,  it is a clear indication of a serious commitment to safety and quality.

Application and Installation

Flooring Types Suitable for Gas Membrane Installation

Reinforced In-Situ Cast Concrete Floors

Reinforced in-situ cast concrete floors are among the most common base types for gas membrane installation. These floors are poured directly on-site, allowing for a continuous surface with minimal joints. The resulting smooth, flat finish provides an ideal foundation for creating an uninterrupted seal with the membrane. This type of flooring is particularly well-suited to achieving airtight protection beneath the membrane layer. Contractors frequently prefer this method in high-risk gas areas due to its proven reliability and compatibility with protective systems.

Suspended Concrete Floors Using Beam-and-Block Systems

Beam-and-block floors consist of precast concrete beams combined with infill blocks to form a suspended structure above ground level. Gas membranes can be laid across the entire floor area prior to the application of any screed or concrete topping. To ensure airtightness, it is crucial to seal thoroughly around the perimeter and at the ends of the beams. This type of floor is particularly effective in areas with uneven or unstable ground conditions. However, additional care must be taken to correctly overlap and tape the membrane to maintain a continuous, gas-tight barrier.

Precast Concrete Slab Flooring

Precast concrete slabs are manufactured off-site and assembled on location, offering a fast and efficient construction solution. Gas membranes may be installed either beneath or above the slabs, depending on the design requirements. All membrane joints must be sealed securely to prevent gas from escaping through any gaps between the slabs. This flooring type is particularly well-suited to large-scale developments where precision and speed are essential. Close coordination between trades is vital to ensure the membrane remains intact and undamaged throughout the installation process.

A Practical Guide to Installing Gas Membranes

The type of gas membrane selected will influence the installation method required on your site. Specialist radon membranes are available for properties located in high-risk radon areas. In some instances, your project may necessitate a dual system, comprising both a general gas membrane and a radon-specific barrier. This decision is typically guided by the findings of a professional site survey. A tailored approach ensures maximum protection and full compliance with building regulations.

Gas membranes should always be installed early in the structural phase, prior to major groundwork or floor construction. The surface must be smooth and level to prevent damage to the membrane. Sheets should overlap by at least 150mm and be sealed using high-quality double-sided tape. Correct sealing is essential to ensure the membrane is both gas- and watertight. As an added benefit, this setup also helps prevent ground moisture from entering the building.

Once all joints are laid and sealed, a single-sided tape should be applied over the top of each overlap to reinforce the seal. This final layer strengthens the bond and creates a continuous, airtight barrier. To avoid accidental damage during the remainder of the build, temporary protective boards should be placed directly on top of the membrane. This protection guards against wear from foot traffic or tools until the next phase of construction begins.

Conclusion

Gas barrier membranes are a crucial defence against hidden ground gases that pose risks to both the structural integrity of your home and the health of its occupants. When installed correctly, they prevent harmful gases such as radon and methane from entering the property, offering long-term protection and ensuring compliance with building regulations. This is not an area where guesswork or shortcuts are acceptable, even minor gaps can compromise the entire system.

Engaging certified professionals and using approved materials is essential to safeguarding your project against costly repairs and serious air quality concerns. Taking proactive steps early in the construction process not only saves money but also delivers lasting safety and peace of mind for years to come.

FAQs

Can I install a gas membrane myself?

No. Professional installation is strongly recommended to ensure airtight sealing and full compliance with safety and building regulations.

How long does a properly installed gas membrane last?

With correct installation and high-quality materials, gas membranes can last for decades—often aligning with the lifespan of the building’s foundation.

What if the membrane is accidentally punctured during construction?

Any puncture must be repaired immediately using compatible sealing products to restore the membrane’s airtightness and protective function.

Are gas membranes necessary in modern urban housing developments?

Yes. Depending on the outcome of site surveys, urban areas may still require protection from gases such as radon or methane due to underlying geological conditions.

Do all building projects require a gas membrane?

Not all projects require one. However, a site-specific ground gas risk assessment will determine whether a membrane is necessary to safeguard health and ensure regulatory compliance.

Users Also Say

Do you put a membrane under concrete?

Ji********ne

“The usual recommendation is to place a sheet of 6-mil plastic before pouring the concrete. This has 2 benefits. It prevents the loss of water from the concrete mix into the soil, which affects the curing process of the concrete. Later the plastic prevents moisture from the ground penetrating through the concrete and making the surface damp. Many people don’t realize that concrete is porous to water.”

Ed***ll

“I would strongly recommend it. I had a new basement floor poured in my basement a few years back, and they laid a plastic sheet under the new concrete. Now, 90% of my water issues have been resolved.”

Bi*****yd

“YES it stops the moisture from coming up through the concrete, sealing off the surface of the concrete underneath. ( Check a broken up slab that has had plastic underneath and see just how smooth it is) Next it stops the water in the mix from draining out into the ground causing racking during curing and makes for a stronger concrete There seems to be a problem in the UK with radon gas, and much is said about how it prevents the gas from coming up through the concrete. While plastic under the slab may help, the commentators seem to forget that it is a gas, and it will simply flow out under the plastic and through any walls into any low cavities such as cellars, which in fact renders the reason for the plastic as invalid”