Abstract: The present invention relates to the use of a solid comprising at least one organosilane and a carrier material to hydrophobise mortars, wherein the organosilane has the formula R1Si(OR?)3 or R1R2Si(OR?)2 wherein R1 and R2 are the same or different and are a linear or branched C1- to C4-alkyl and/or alkenyl group, OR? is an acetoxy, a C1- to C4-alkoxy and/or a C2- to C6-methoxyalkoxy and/or ethoxyalkoxy group, and the carrier material is a solid at room temperature. The amount of cement in the final formulation is zero or less than 5 wt.-%, based on the total weight of the final formulation in the dry and uncured form. Claimed are also a powder comprising the silane and a carrier with the carrier being a water-soluble polymer, dry mortar formulations containing no or less than 5 wt.-% cement, based on the dry weight of the uncured mortar formulation, as well as processes to manufacture the formulations and/or compounds.