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Gas Membranes
Monarflex RAC Membrane


Monarflex® RAC is part of Icopal’s Monarflex® gas control systems and may be used loose-laid with ground supported or suspended slabs, and is satisfactory for use as a damp proof membrane, and when properly sealed and detailed it will provide an effective barrier to the passage of methane, radon, air and moisture from the underlying soil. It is also suitable for dealing with volatile organic compounds (VOCs).

Monarflex® RAC is manufactured from four layers of virgin low- density polyethylene (LDPE) with a 12 x 12mm multifilament polyester (1670 dtex) reinforcing grid between to give high strength and tear resistance. The membrane also incorporates a 12 µm aluminium foil for low permeability to gases. The top surface is grey-coloured and ribbed, while the underside is grey with a smooth finish.


Monarflex® RAC is manufactured to last the lifetime of the  construction provided it is correctly installed and not damaged by subsequent building operations


Monarflex® RAC may be laid over or under the concrete slab. When laid below slab Monarflex® RAC should be placed on top of a gas permeable layer, such as hardcore blinded with well compacted sand. When placed above slab, the concrete should be dense, smooth and free from any projections which may damage the membrane. Monarflex® RAC should then be covered with a screed or other suitable protective layer. Membranes should be installed in accordance with the manufacturer’s guidelines.

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