The improvement in the physical and mechanical properties of a calcareous soft sandstone upon treatment with synthetic resins: two ethyl silicates, a polymethylmethacrylate, an alkyl methoxysilane, and two silicones has been evaluated. The composites obtained exhibit an unpredictable behavior under prolonged exposure to water. The water absorbed (or adsorbed) has a general tendency to annul the consolidating influence of the resins introduced within the stone. In the case of polymethyl-methacrylate and methylphenylsilicone, the linear strains produced are significantly in excess of that for the untreated stone. This swelling depends not only upon the quantity of water absorbed but also on the mode of its interaction with the stone structure. -- AATA