During the last decade intense weathering has occured on red-brown arkosic sandstones on historical buildings and statues in central Bohemia, for which the action of chemically corrosive substances from the atmosphere, of groundwater and of physical factors is responsible. Weathering products are also soluble salts which migrate from the interior of the weathering rock to its surface, and together with contaminants from the atmosphere they produce a less permeable hard surface layer. The crystallization of gypsum, the cyclical change of humidity in the presence of substances undergoing hydration, high temperature gradient, considerable heterogeneity of the system and freezing of the water lead to the separation of the hard surface layer and denudation of the crumbly lower layer.