The paper deals with the mechanical characterization of timber elements based on bending and compression tests, according to UNI and ISO codes. The investigations were performed on both structural elements and defects-free specimens, made of old chestnut wood, aiming at evaluating the influence of typical defect patterns and wood anatomy on the elastic characteristics, strength properties as well as failure mechanisms of the material. In particular, the behaviour in compression of clear wood under uniaxial loading is studied with different orientations as respect to the longitudinal, radial and tangential directions. The experimental results are examined in relation with the standard values assumed by Italian codes for the quality classes assignment by visual grading.