Depending on the temperature, moisture of the surrounding atmosphere may condensate or not. A piece of wood may thus be in contact either with liquid water during the night for a given time, or with air during daylight at a given relative humidity. A sorption-desorption history of moisture may thus occur, with a moisture content in the wood which may vary to a high extent below or beyond the fiber saturation point. A model based on a finite difference model is able to describe the process : the kinetics of the sorption-desorption history is in good agreement with the experiments ; moreover, a fuller insight into the nature of the process is gained with the profiles of moisture content in various places of the wood sample.