A method for sealing piles in foundations in the construction field, wherein a hollow-body formwork element is used. The method includes: 1) applying a barrier layer to the foundation; 2) introducing a pile into the foundation, the pile being arranged so as to penetrate the barrier layer; 3) applying a hollow-body formwork element along the central longitudinal axis of the pile, the hollow-body formwork element surrounding the pile; 4) introducing mineral binding agents into the intermediate space between the pile and the hollow-body formwork element; 5) connecting the barrier layer and the hollow-body formwork element. The hollow-body formwork element has on the side facing the pile a contact layer, which includes a composite layer of a porous material and/or a sealant. The hollow-body formwork element can remain as a part of the structure and thus can perform a sealing function.