Solvent based, siloxane based salt and water repellent recommended for concrete, masonry, or natural stone. VOC < 400 g/L. Dries natural.


Waterstopper S-20 is a ready to use, penetrating, colorless, non-yellowing, and breathable concrete and masonry siloxane based water repellent treatment compound. Once applied, Waterstopper S-20 chemically reacts with the substrate and forms long life water repellent groups that cross-link into a polysiloxane compound. Surfaces treated with Waterstopper S-20 are protected against the damaging effects of water intrusion, de-icing chemicals, freeze-thaw exposure, acid rain, airborne impurities and most other atmospheric chemicals without altering the appearance or texture of the treated substrate. Waterstopper S-20 is formulated to protect vertical above grade concrete and masonry surfaces such as precast, shotcrete applications, tilt up and monolithic concrete, concrete block, stone and brick masonry, as well as protecting horizontal concrete wearing surfaces. Waterstopper S-20 is for exterior use only.


  • V.O.C. compliant.
  • Excellent chloride / salt resistance.
  • Exhibits very high water repellency.
  • Low evaporation rate allows higher penetration.
  • Treated substrate is less absorbent and more resistant to freeze-thaw cycling damage.
  • Will not darken concrete leaving a more natural appearance.
  • Works inside the concrete matrix leaving no film or resins at surface that can chip, peel, discolor, or wear.

COMPOSITION: Oligomeric alkylalkoxy siloxane in aliphatic/acetone VOC compliant blended carrier solvent.

COVERAGE: Waterstopper S-20 is designed for a one coat application on all substrates listed below. The only exception to a one coat application procedure is for materials having low density or high permeability such as concrete block or porous clay brick, in which case a second application may be necessary depending on absorbency*. The following coverage rates are approximate and for estimating purposes only. We recommend that a test application is made on the actual surface to be treated to accurately determine coverage rates, effectiveness and influence on surface appearance

 SURFACE TYPE  COVERAGE (sq. ft./gal)  SURFACE TYPE  COVERAGE (sq. ft./gal) 
Concrete – Bridge Decks / Ramps *175-225 Natural or Cast Stone 75-125
Concrete – Block* 50-100 Precast Paver Block 150-200
Clay Brick – Porous* 60-120 Stucco 75-100
Clay Brick – Dense 100-120 Artificial Stone 50-100
*Approved by Illinois Dept. of Transportation for Concrete Sealer at 225 ft2/gallon (5.5 m2/l)

SHIPPING NAME: UN 1090, Contains Acetone, Flammable, 3, PGII

SHIPPING CLASS: Item #155250 Sub 2 LTL 65

AVAILABLE IN:  1 Gallon (3.78 L), 5 Gallon (18.9 L) pails, 55 gallon (208 L) drums