Abstract: A flexible seal for constructions and method of using such seals where the seals include a mixture of soil and a polymeric additive including polymeric methacrylamide, which additive opens a water casing around soil grains, wherein 1 m3 of soil contains up to 0.5% by volume of the additive wherein the additive also contains saponified paraffins or further contains between 15 kg and 25 kg of cement and/or lime per 1 m3 of soil which cement and/or lime in turn contains 1% by weight to 10% by weight of the additive or wherein a proportion of between 20% by weight and 50% by weight of water is added to the mixture to make it capable of flow.