Water is the most dangerous factor for buildings. Each penetration into the building structures results in a number of problems, from technical and economic to health-related ones. Issues related to the drying of buildings are very complicated. This is mainly due to the way in which different construction and finishing materials react to water and moisture as well as the causes and sources of moisture. In this chapter, natural and artificial, both invasive and non-invasive, methods of building dehumidification have been characterised, together with presenting technical methods of performing such treatments and a brief discussion of their advantages and disadvantages.