An aqueous emulsion for waterproofing a surface comprising: a) 1 to 85% by weight of an alkylalkoxysilane of the formula R1aSi(OR2)4−a b) 0.1 to 10% by weight of a cationic alkoxysilane of the formula R3bR4Si(OR5)3−b c) up to 20% by weight of a hydroxy terminated polydimethylsiloxane having a degree of polymerization from 1 to 500, said hydroxy terminated polydimethylsiloxane being present in the aqueous emulsion where; R1 is an alkyl group containing 1 to 30 carbon atoms, R2 and R5 are independently selected from the group consisting of hydrogen, alkyl groups containing 1 to 4 carbon atoms, CH3C(O)—, CH3CH2C(O)—, HOCH2CH2—, CH3OCH2CH2—, and C2H5OCH2CH2—, R3 is an alkyl group containing 1 to 4 carbons, R4 is a monovalent hydrocarbon having at least one quaternary ammonium group substituent, a is 1 or 2, b is 0, 1 or 2.