A sealant is arranged in a meshlike manner between a composite layer and a barrier layer in a water-tight membrane that includes a barrier layer and a composite layer. In the case of a leak in the barrier layer, the network of sealant between the composite layer and the barrier layer prevents the barrier layer from being affected. As a result, the size of the areas affected by penetrating water is limited. The damage by the penetrating water is thus limited to a smaller area, and the point of damage can thus be more easily localized.