Abstract: A sealant composition especially useful for porous materials such as wood, concrete and mansonry is provided comprising: (a) a silanol-terminated polysiloxane having a molecular weight greater than about 2000; (b) a multifunctional silane having functional groups which condense with silanol groups in the presence of atmospheric moisture at room temperature to form a cross-linked polymer; and (c) a nonaqueous volatile solvent which is non-reactive with components (a) and (b).The sealant composition renders said materials waterproof by coating and filling in the pores of said material with cured silicone rubber product.In a preferred embodiment the composition also contains a metal-containing curing catalyst and a volatile or subliming chelating agent in an amount sufficient to prevent cure of the composition in the storage container prior to or during use.The composition may also comprise adhesion agents, surfactants and pigments.