Coating compositions for cementitious substrates may be made from a multistage latex polymer; silane; and a water-soluble acid, acid anhydride or acid salt capable of etching or otherwise reacting with the surface of the substrate to provide improved coating adhesion. The silane may be present as a silane coupling agent distinct from the multistage latex polymer, or may be present as silane functionality on the multistage latex polymer. The coating compositions adhere well to cementitious substrates and have a self-etching capability which improves coating adhesion, especially near edges and corners.