In this paper, the strength and the weight effectiveness for the plywood I-core sandwich structure is elaborated. For the plywood sandwich concept the plywood sheets are used at the outer surfaces to maximize rigidity while introducing in between adhesively bonded plywood stiffeners to keep the whole sandwich structure together. The structural stiffness capacity and weight efficiency are elaborated for the pure plywood structure and the I-core sandwich panel with the corresponding height and width dimensions. A metamodelling procedure is applied by approximating the finite element stiffness response values with parametrical functions employing the Adaptive Basis Function Construction approach. The resulting design procedure provides an effective optimal design tool that enables to estimate the stiffness and the weight optimum solutions.