Provided are highly water-resistant, flexible cementitious coating compositions comprising: an aqueous styrene-butadiene latex, one or more epoxy silane, cement, and one or more solid filler. The epoxy silane may comprise one or more epoxy functional groups and one or more hydrolysable functional groups selected from siloxy, silane, and, silanol or combinations thereof. Also provided are kits comprising the components of the cementitious coating compositions, methods for providing coatings, layers or membranes derived from such wet compositions, as well as the coatings, layers or membranes derived therefrom.