The invention relates to water-redispersible polymer powder compositions obtainable by means of free-radical-initiated polymerization in aqueous medium of one or more monomers from the group consisting of vinyl esters of unbranched or branched alkylcarboxylic acids having from 1 to 15 carbon atoms, methacrylic esters and acrylic esters of alcohols having from 1 to 15 carbon atoms, vinylaromatics, olefins, dienes and vinyl halides and subsequent drying of the polymer dispersion obtained, characterized in that one or more silanes of the general formula (RO).sub.3-nR.sup.1.sub.nSiR.sup.2X (1) are added before or during the polymerization or before drying of the polymer dispersion, and also their use in tile adhesives.