The actively developing market of timber construction requires modernization, invention and implementation of modern materials and new basis of design. One of the most promising solutions for structural elements of timber structures are I-beam and tubular girder sections. In the work, beams are considered box-sectioned, the belts of which are made of solid wood, and the walls of oriented-strand boards. A comparative analysis of the stresses calculated by the domestic standard method and obtained from the solid finite-element model in the PC Lira is presented. In the calculation with software complex, the anisotropic properties of wood and OSB are taken by specifying the orthotropic properties of materials.