FIELD: manufacture of building materials. SUBSTANCE: invention relates to materials increasing water-proofing properties of one-piece or fabricated reinforced-concrete structures operated under high-humidity conditions (with inside or outside backwater). Cementing composition of invention is intended for use when performing construction work or emergency repair work and contains, wt. pts: binding agent (white cement, Portland cement, or their mixture), 100; filler (arenaceous quartz or feldspar sand), 6-30; water-proofing additive (sodium methyl siliconate), 0.2-1.0, and water, 30-35. Water is added immediately before work. Specific surface of binder and filler is 2-3 sq. m/g. Resulting coating thin (1 mm thick) and strong (compression strength up to 65 MPa). EFFECT: increased water resistance. 2 tbl
