Multilayer membrane for construction

A multilayer membrane suitable for construction, adapted to be installed between a wall of a seat obtained in the ground and a concrete structure, the membrane comprising:

• a first layer comprising thermoplastic polymeric material, impermeable or substantially impermeable to water;
• a second layer comprising thermoplastic polymeric material, impermeable or substantially impermeable to methane gas, fixed to the first layer and adapted to be positioned, when the membrane is installed, between the first layer and a concrete structure,
• wherein said multilayer membrane further comprises:
• a drainage layer comprising a bulged membrane fixed to the first layer on the opposite side of the second layer, and adapted to be positioned, when the membrane is installed, in contact with the wall of a seat obtained in the ground, to drain possible liquids present in the seat,
• wherein
• the first layer and the second layer do not comprise bulges and the bulges present in the bulged membrane have a height of from 1 mm to 5 mm,
• the second layer has a multilayer structure comprising:
• a third layer comprising thermoplastic polymeric material impermeable or substantially impermeable to water;
• a fourth layer comprising thermoplastic polymeric material impermeable or substantially impermeable to methane gas and/or to radon gas and/or one or more volatile organic compounds, positioned between the third layer and the first layer;
• a fifth layer comprising thermoplastic polymeric material impermeable or substantially impermeable to water, positioned between the fourth layer and the first layer;
• a sixth layer comprising thermoplastic polymeric material impermeable or substantially impermeable to methane gas and/or to radon gas and/or to one or more volatile organic compounds, interposed between the fourth layer and the fifth layer;
• a seventh layer comprising thermoplastic polymeric material impermeable or substantially impermeable to methane gas and/or to radon gas and/or to one or more volatiles organic compounds, interposed between the sixth layer and the fifth layer;
• wherein the fourth layer has a melting temperature higher than that of the fifth layer,
• wherein the fourth layer has a melting temperature higher than 135° C.,
• wherein the fifth layer has a melting temperature comprised between 100° C. and 135° C.,
• wherein the seventh layer has a melting temperature higher than that of the fifth layer,
• wherein the seventh layer has the same composition as the fourth layer.