A method for producing a profiled semi-finished plastic product from flexible web material, comprising: - providing a plurality of webs of flexible material; - continuously and simultaneously feeding the webs of material to and along a plurality of shaping pieces arranged next to each other, preferably having greatest transverse dimensions which are smaller than the width of a web of material; - folding the webs of material around respective shaping pieces to form bodies and edge strips (13, 14) which project transversely with respect to the bodies, including: - folding the webs of material around a side of the respective shaping pieces to form first edge strips which project transversely with respect to the bodies; - folding the webs of material around another side of the respective shaping pieces to form second edge strips; - causing the first edge strips at said one side of the shaping pieces to cover each other; - causing the second edge strips on said other side of the shaping pieces to cover each other; causing the edge strips (13,14) of different webs of material to at least partly cover each other; - impregnating the provided webs of flexible material or the assembly of webs of material with folded-over edge strips (13, 14) covering each other with a hardenable means; - causing the hardenable means to harden to form the profiled semi-finished plastic product, in such a manner that hollow spaces remain, which are in each case defined by two neighbouring bodies and edge strips (13, 14) in the formed profiled semi-finished plastic product. - providing a plurality of webs of flexible material; - continuously and simultaneously feeding the webs of material to and along a plurality of shaping pieces arranged next to each other, preferably having greatest transverse dimensions which are smaller than the width of a web of material; - folding the webs of material around respective shaping pieces to form bodies and edge strips (13, 14) which project transversely with respect to the bodies, including: - folding the webs of material around a side of the respective shaping pieces to form first edge strips which project transversely with respect to the bodies; - folding the webs of material around another side of the respective shaping pieces to form second edge strips; - causing the first edge strips at said one side of the shaping pieces to cover each other; - causing the second edge strips on said other side of the shaping pieces to cover each other; causing the edge strips (13,14) of different webs of material to at least partly cover each other; - folding the webs of material around a side of the respective shaping pieces to form first edge strips which project transversely with respect to the bodies; - folding the webs of material around another side of the respective shaping pieces to form second edge strips; - causing the first edge strips at said one side of the shaping pieces to cover each other; - causing the second edge strips on said other side of the shaping pieces to cover each other; - impregnating the provided webs of flexible material or the assembly of webs of material with folded-over edge strips (13, 14) covering each other with a hardenable means; - causing the hardenable means to harden to form the profiled semi-finished plastic product, in such a manner that hollow spaces remain, which are in each case defined by two neighbouring bodies and edge strips (13, 14) in the formed profiled semi-finished plastic product.