GAS MEMBRANE

Gas membrane is a chemically resistant, loose laid plastic sheet barrier used to provide protection against harmful ground gases like radon, hydrocarbons, methane and carbon dioxide. It also acts as a damp proofing membrane, protecting properties from moisture ingress. In fact, those multi-functional membranes protect people from gas contamination. It is generally used within construction applications, predominantly within the foundation design. The membrane is a loose-laid and suitable for use in most horizontal and some shallow vertical including beneath reinforced concrete slabs and associated foundations. Generally, the loose laid systems are sealed with a range of double sided tapes or seam welded, complying with the latest codes of practice as published by BS 8485: 2015, CIRIA & BRE. Gas and radon proof membranes are designed to be installed in concrete ground floors, either above or below the slab. They should therefore be considered at an early structural planning stage. The barrier is usually coloured blue or red on the upper surface and silver on the reverse. Gas membrane is also qualified as a low risc CS2 passive gas protection (<30m span). The most popular gas membranes in the UK are Visqueen and Cordek followed by Novia 1200g Radon Gas Barrier. While Visqueen offers an average cost of £4.31 per m2, Cordek with its Tri-Gas Membrane seems to be more expensive costing £5.20 per m2. On other hand Novia's equivalent product price is 1.03 per m2. All details can be found in manufacturers datasheets.  

GAS MEMBRANE GAUGES

Gas membrane comes in a choice of two standard gauges, 1000 gauge (250 Micron thick) and 1200 gauge (300 Micron). The thickness of a gas membrane is expressed in gauge or microns and the higher the gauge/microns, the thicker the polythene. The gauge was the traditional imperial measurement of polythene thickness but has now been replaced by micron as the European metric standard. The gauge of polythene can easily be converted to a micron measurement by dividing it by four. Furthermore, if you want the thickness in millimetres then just divide the gauge by 4000. As an example, 1000 gauge = 250 micron = 0.25mm. The 1200 gauge membrane has a  thickness of 300μm, making it highly puncture resistant. On smooth or blinded surfaces, membrane will not be damaged by normal foot or site traffic such as wheelbarrows, while 250-micron sheet is still considered a "HEAVY DUTY polythene and ideal for heavy-duty applications such as a damp proof membrane and industrial gas protection.

TYPES OF GASES

RADON 

Radon is an invisible radioactive gas that is formed when the small amounts of uranium in rocks and soils decays. It is found everywhere, but at varying levels. Radon can cause health issues, including increasing the risk of cancer in certain instances. Radon is a naturally occurring gas that can seep into buildings through cracks in the foundation or through a water supply. It is considered dangerous because it becomes more potent when in an enclosed environment. These gases can occur naturally or be a result of contamination of the land such as on brownfield sites or landfill sites where waste has been buried. Radon Membrane is one of the types of gas membranes, for use in applications where resistance to radon gas is required as a full radon protection system. The UK Health Security Agency has published a map showing where high levels are more likely. Please note, some areas of the UK have a greater chance of high radon levels and new build properties in these locations need protecting. The darker the colour the greater the chance of a higher level. The chance is less than one home in a hundred in the white areas and greater than one in three in the darkest areas. 

CARBON DIOXIDE/METHANE

Carbon dioxide and methane are commonly found in rocks and soil. Methane also poses a further risk as it is flammable. 

GAS MEMBRANE MANUFACTURERS

There are numerous manufacturers of gas membranes, providing several different types including Radon Barrier Membranes, liquid gas membranes, self-adhesive gas membranes and Gas DPCs. All rolls of the gas membrane that we sell are uniquely labelled and registered, providing complete traceability. This means that they can be installed safely in the knowledge that the product has been independently tested, certified and carries BBA and ISO9001 approval.

NOVIA

Novia Radon 1200G is a high-quality CE approved Gas Barrier and Damp Proof Membrane designed for solid concrete ground floors that are not subject to hydrostatic pressure. This 300 Micron Radon Gas Barrier and DPM meets Building Research Establishment (BRE) and Building Regulations requirements for use as a gas control membrane against radon. The 1200 gauge Novia Radon Gas Protective Membrane is made using premium quality blown polythene polymers and is approved to EN 13967:2012.

VISQUEEN

Visqueen Gas Barrier is a multi-layer reinforced polyethylene gas barrier with a 20 micron aluminium foil. The barrier is coloured blue on the upper surface and silver on the reverse. The product is supplied in single wound rolls (not folded), 2m x 50m.

CORDEK

Tri-Gas Membrane is a high performance gas membrane for use in situations where resistance to methane, carbon dioxide and/or radon gas is required. It is generally used within construction applications, predominantly within the foundation design. The multilayer 0.4mm thick membrane includes an ultra-low permeability aluminium foil core encapsulated between a number of additional LDPE layers and a reinforcing grid to form a single sheet membrane.

DELTA

Delta Membrane Systems Limited offer a comprehensive range of ground gas protection solutions along with its structural waterproofing solutions. From Memtech ground gas membranes to waterproofing systems, the product range is designed to deal with all ground gas, contaminants and waterproofing related problems.

GAS BARRIER INSTALLATION

It is vitally important that all joints are sealed including under wall sealing. Unroll the first membrane. Make sure that it is laid on a smooth surface or one that has been sand blinded to prevent any punctures. Inspect it carefully to make sure that there are no indentations or protrusions. You should also ensure the surface is free from dust or grease, and is completely dry. Unroll the second membrane, overlapping the first membrane by 150mm. Ensure that both membranes remain dry and free from dust and dirt at all the times. Remove the protective paper from the Double Sided Tape. Now apply pressure to the membrane in order to join the two membranes together. Every joint between gas membranes needs to be made gas tight in this way with the double-sided tape. You can now use a single-sided tape to seal the top join of the membranes. This creates an airtight seal. It also stops the section of overlapping membrane from flapping up and the screed getting between the two sections of membrane. If you have any pipework coming through the slab and the radon barrier sheet then you need to take further measures to ensure gas can’t escape. Cut a hole in the membrane as close to the size of the pipe as possible. When the pipe is in place, you can use top hat fittings over the pipes alongside gas tape to ensure a gas tight seal. 

SCREWFIX