The invention relates to water-repellant liquid silicone compositions intended for impregnating porous building materials, such as mineral or (ligno)cellulosic materials And comprising epoxy functionalized polyorganosiloxanes as main active material in these water-repellant liquid silicone compositions. The invention also relates to a process for making said porous building materials, water-repellant with the aid of the above said liquid silicone composition, and a process for preparing this composition is also targeted by the invention.