Abstract: The invention relates to a method of manufacturing a composite building element that includes a casing material, a bulk material, and a locking element, the method including the steps of: (a) continuously feeding a first sheet of casing material into a filling station; (b) securing the bulk material to the first sheet of casing material; (c) continuously feeding the bulk material and the first sheet of casing material out of the filling station; the method characterized by the step of: (d) securing the locking element to the first sheet of casing material prior to securing the bulk material to the first sheet of casing material.