The occurrence, extent and concentration of gases such as Radon / Methane and Carbon Dioxide are essential considerations in the design and installation of any waterproofing system as applied to the foundation zone of any structure.

Methane and Carbon Dioxide are commonly found naturally close to organic strata such as those containing slate,, coal seams and peat areas. High concentrations can also be found at or in close proximity to Brownfield sites which were previously occupied by Industries processing for example – Hydrocarbon materials such as Coal, Oil etc. Concentrations and traces of these gases with their associated impurities can also be found in locations associated with Landfill sites where rotting vegetation and putrescibles are a major source of organic leachate, lixiviant and methane.

Gases are generally lighter than air and migrate upwards and laterally until they either form concentrations in occluded pockets within soil masses or foundation areas or they naturally vent and disperse in to the atmosphere.

Obviously the concentration and trapping of gases in the foundation zones of areas where structural development is to be considered poses a potentially hazardous situation and health risk. It is therefore important and a requirement of law that precautions are taken to avoid any dangers which may be associated to Health and Safety as a direct consequence of substances which are found in the ground over which building or structural work is intended.

Membrane systems , which constitute a permanent barrier as well as control the flow to an otherwise uncontrolled migration and concentration of gases are essential elements to the long –term Health and Safety of any development and have now become a requirement by law. These durable membrane systems prevent the passage of gases through the foundation zone and into the building through fissures, construction joints and other migratory pathways.

Enviro Seal has secured an exclusive supply partnership for the Supply and Installation of Radon and Methane barriers including the provision of all the necessary ancillary items such as gas resistant taping systems / Sumps / cavity adaptors/ Elbows/ T –Joints/ Ducting and much more which are required by design to manage and evacuate the flow of gas and to resist the propensity for gas corrosion for at least the service life of the building.

Vertical Cut-off Membrane Barriers

By way of a further alternative to the solutions offered by the examples in the previous section, which are essentially horizontally laid membrane barriers which extend to just beyond the footprint of the building and its immediate foundation works, Vertical barriers and cut-off curtains are, as the name implies, barriers which prevent the horizontal flow of liquids and gases through porous soil media.

These barriers normally encircle large areas of development either to prevent outflow of effluent and gas or to prevent inflow into new areas of development. These barriers are normally constructed below the surface and extend vertically to the first known impermeable strata which is capable of preventing the underflow of effluent and gas below the toe of the installed curtain.

These barriers are generally prefabricated from thicker sections of membrane often with interlocking connections which are installed into vertical trenches by a mandrel or other installation device. The trench in these situations is often kept open by means of a continuous Bentonite slurry into which the curtain sections are “driven”.

Once completed , the wall offers a cost-effective , long term chemical and gas resistant barrier to the flow of contaminants and gases and is a significantly cheaper alternative to the more conventional and traditional systems using steel pile wall techniques.

Typically, Linings which fall into this category can be divided , but certainly not limited to the following groups : Restoration works/ Methane and Radon gas barriers/ Foundation and building works/ Cut-off membranes/ Brownfield developments/ Sheet piled walls/ Cut-off barriers.

Enviro Seal can advise and recommend on the most cost-effective, safe and appropriate lining solutions to meet clients specific requirements. Contact Enviro Seal now for a fully professional service relating to advice on product selection, capability profiling and quotations for the supply and /or installation of lining solutions for specific projects.

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