The master thesis deals with the evaluation of thermal resistance of selected wood materials before and after retardation, while the selected issue is solved on the theoretical and practical level.The theoretical part of the thesis is devoted to the issues related to wood and materials based on it, namely the basic characteristics, properties and use of the mentioned materials. There are also described methods of fire protection of these materials. Subsequently, the theoretical part is followed by the practical part of the thesis, which brings the results of experimental evaluation of thermal resistance of unprotected and retarded samples of spruce wood and OSB board. For this purpose, was used protective substance ISONEM ANTI-FIRE PAINT. Its effectiveness was monitored depending on the varying concentration and the number of coatings applied. As evaluation criteria we used the weight loss and the ignition time of the tested samples, at their exposure to radiant heat source.The results of the experimental evaluation of thermal resistance point to a variant of the samples with the most effective retardation, compared to the samples without the retardation. From the four variants of spruce wood samples, the total average lowest weight loss has a sample of two 100% paint coat, thus proving to be the most effective. From the four variants of OSB board sample, the average percentage of the lowest weight loss has a sample with two 75% paint coat.