Highly water-resistant, flexible cementitious coating

A kit comprising:

• an aqueous styrene-butadiene latex;
• one or more epoxy silane;
• cement;
• and
• one or more solid filler;
• wherein the one or more epoxy silane comprises one or more one epoxy functional group and one or more hydrolysable functional groups selected from the group consisting of siloxy, silane, silanol, and combinations thereof;
• and
• wherein the aqueous styrene-butadiene latex and the one or more epoxy silane are contained in a first pack and wherein the cement and one or more solid filler are contained in a second pack.

A dry, water-resistant, flexible cementitious coating, layer or membrane comprising:

• a styrene-butadiene copolymer;
• hydrated cement;
• one or more solid filler;
• and
• one or more epoxy silane, or a residue of the one or more epoxy silane, wherein the one or more epoxy silane comprises at least two epoxy functional groups and at least two hydrolysable functional groups selected from the group consisting of siloxy, silane, silanol and combinations thereof.