The thesis deals with the process analysis of thermally modified beech wood and the assessment of its usage in building construction. Contains description of beech forest, information about processes used for thermal modification and about attributes of thermally modified wood.There is also a methodology developed, evaluated strength properties in the four-point bend where the experimental work was done according to the STN EN 408 standards. Consideration of the use of thermally modified beechwood lumber, based on results of the performed experiments and their selected mechanical properties as structural timber.The main idea of the thesis is to explore level of change in strength properites of beech forest wood (Fagus sylvatica) after modification of the thermal modification process and the usage of this wood in practice.At the end of the thesis, the experimentally measured data are summarized, including the interpretation of the results and the comparison to literature