Firewood is dried only naturally because natural timber drying is much better than the artificial one from the point of view of preservation of all natural features of timber. Moreover, when timber is dried it shrinks up to 5% in its width and thickness. Therefore if it is dried too fast there is a risk that moisture in the internal layers deep in timber will not manage to escape to the surface layers that, as a result of lack of moisture, will just shrink and close the door for moisture that is in deeper layers. Thus, upper layers will continue drying whereas the internal layers will be as if closed. As drying in drying-houses requires quite many funds, many manufacturers do not dry timber for a necessary period of time in order firewood would become completely dry. When measuring moisture content at the surface of firewood it seems that it is dry but when the storing conditions are changed or firewood is stored in storerooms with poor ventilation, etc. moisture from internal layers comes to the surface what causes mold to grow. Under natural conditions, firewood dries evenly. Some firewood may be slightly more humid than firewood dried in drying-houses but mold will never grow on it.

For natural firewood drying, flat, high place with slight slope for water to flow down is chosen. Firewood containers are stacked a certain distance away from each other, and the rows are oriented so that the prevailing winds in that place would blow across the containers. Each container has a foundation with empty cavity underneath. Firewood stored under such conditions dries naturally and mold does not grow on it. Duration of the drying process depends on species of the trees and on thickness of the material. Duration of natural drying process of firewood also depends on the climate and weather.