Method for providing a moisture barrier for protecting a landfill from penetration and/or egression of moisture, comprising the steps of: a) providing a backing layer for covering the landfill; a mineral layer for covering said backing layer; a synthetic layer for covering said mineral layer; a drainage layer for covering said synthetic layer; and a top layer for covering said drainage layer; and b) covering said landfill in consecutive order with the backing layer, the mineral layer, the synthetic layer, the drainage layer and the top layer, characterized in that the sodium adsorption ratio in the backing layer is determined before covering the backing layer on the landfill with the mineral layer, with the sodium adsorption ratio having a value below 8, and wherein said mineral layer has a hydraulic conductivity of between 3,86E-10 and 1E-12 m/s, and in that for the synthetic material in the synthetic layer the following is determined: i. the tensile strength after 0 hours and after between 1.000 to 3.000 hours incubation at 100°C, said tensile strength being at least 250 kJ/m 2 at all time-points; ii. the strength in a tensile impact test after 0 hours and after between 1.000 to 3.000 hours incubation at 100°C, said strength in a tensile impact test being at least 250 kJ/m 2 at all time-points; and iii. the tensile strength after an oxidative induction time of 0 hours and after between 1.000 to 3.000 hours at 100°C in air, said tensile strength after an oxidative induction time of between 1.000 to 3.000 hours being at least 75% of the tensile strength after an oxidative induction time of 0 hours. a) providing a backing layer for covering the landfill; a mineral layer for covering said backing layer; a synthetic layer for covering said mineral layer; a drainage layer for covering said synthetic layer; and a top layer for covering said drainage layer; and b) covering said landfill in consecutive order with the backing layer, the mineral layer, the synthetic layer, the drainage layer and the top layer, characterized in that the sodium adsorption ratio in the backing layer is determined before covering the backing layer on the landfill with the mineral layer, with the sodium adsorption ratio having a value below 8, and wherein said mineral layer has a hydraulic conductivity of between 3,86E-10 and 1E-12 m/s, and in that for the synthetic material in the synthetic layer the following is determined: i. the tensile strength after 0 hours and after between 1.000 to 3.000 hours incubation at 100°C, said tensile strength being at least 250 kJ/m 2 at all time-points; ii. the strength in a tensile impact test after 0 hours and after between 1.000 to 3.000 hours incubation at 100°C, said strength in a tensile impact test being at least 250 kJ/m 2 at all time-points; and iii. the tensile strength after an oxidative induction time of 0 hours and after between 1.000 to 3.000 hours at 100°C in air, said tensile strength after an oxidative induction time of between 1.000 to 3.000 hours being at least 75% of the tensile strength after an oxidative induction time of 0 hours. i. the tensile strength after 0 hours and after between 1.000 to 3.000 hours incubation at 100°C, said tensile strength being at least 250 kJ/m 2 at all time-points; ii. the strength in a tensile impact test after 0 hours and after between 1.000 to 3.000 hours incubation at 100°C, said strength in a tensile impact test being at least 250 kJ/m 2 at all time-points; and iii. the tensile strength after an oxidative induction time of 0 hours and after between 1.000 to 3.000 hours at 100°C in air, said tensile strength after an oxidative induction time of between 1.000 to 3.000 hours being at least 75% of the tensile strength after an oxidative induction time of 0 hours.