The final thesis is focused on measuring wood char depth for fire investigation purpose in wooden houses. The theoretical part of the thesis presents knowledge about the main topic – legislative acts and documents related to the fire investigation issue in the Slovak republic (organizational support and fire investigation procedure, documentation of a fire scene, assessment of fire statistics), chemical composition and structure of wood. Furthermore, elucidates wooden houses (basic construction systems, their advantages and disadvantages), thermal degradation of wood, fire impact on wooden houses and the char depth. The experimental part of the thesis deals with the char depth and charring rate of tested samples. The object of testing were three samples of spruce wood, respectively exposed to radiant heat flux for time intervals of 30, 45 and 60 minutes. The wood char depth was determined by measuring with a dial calipers with depth probes and retractable metric ruler. The results show, that there is a linear addition between the wood char depth and the time the sample was exposed to radiant heat.