Provided is a composition for coating that can form a waterproof siliceous coating film. To impart water resistance to a film formed by binder of alkali silicate, radioactive material is used in combination with the binder. Additionally, inorganic filler, inorganic body pigment, inorganic color pigment, additive, and water are used in combination, thereby attaining a coating film that combines water resistance, acid resistance, and non-flammability.