A semi product for building panels or structural elements comprising several wood lamellas (5) fixed by distance elements (4), a building panel with such a semi product and a method of producing the semi product and the building panel. A method of producing a semi-product for a structural element or for a core for a building panel, wherein the method comprises the step of: attaching at least two distance strips by an adhesive to a first wood board; attaching a second wood board to the distance strips by an adhesive; and cutting the first and the second wood boards and the distance strips in the length direction of the wood boards.