The aim of this thesis deals with the evaluation of the facade fiberboard STEICO protect producing from the company STEICO, in terms of its wetness under the given conditions. It's absorption due to adverse weather (rain), it's drying time and consequently its adherence to the base layer of the plaster (the reinforcing mortar Capatect 133). This thesis provides the minimum amount of time necessary for the drying of the facade fiberboard STEICO protect while the board is exposed to adverse weather conditions. All results of this thesis were evaluated in Microsoft Excel. When measuring moisture absorption, we found that the test bodies are approximately the equilibrium moisture content after 21 days after when we placed in an environment with constant parameters. When we measured the absorbency we found, irrespective of the duration of the soaking of the fiberboard, the drying time lasts at least 2 weeks. Although the surface moisture was approaching equilibrium humidity after 1 day, average moisture not yet, and therefore it is not enough to measure only the surface moisture of the fiberboard. The fact also remains the tensile strength is highest in the normal test bodies. It is meaning that the fiberboard should not be exposed to adverse weather. The results of this thesis can be used, for example, in construction or in science of wood technology.