Penetrating Primer and Water Repellent for Concrete and Masonry


Si-Prime is a water-borne blend of silanes, siloxanes and acrylics used for priming porous concrete and other mineral substrates.

Si-Prime impregnates the surface making the penetrated zone hydrophobic (water repellent) that creates a dry zone beneath the coating. This is an additional layer of waterproofing protection for the substrate to the topcoat applied subsequently.

The dry zone created by Si-Prime helps protect the topcoat underside from salts and alkalis that can be transported to the surface.

Being of low viscosity, Si-Prime penetrates well into the substrate and once cured allows entrapped moisture in the substrate to outgas as moisture vapor.

Si-Prime also helps bind and consolidate weak or powdery surfaces.

Fully compatible with Si-Rex03 Silicone Resin Emulsion Paint, Si-Prime helps equalize surface porosity to allow a more even application of the topcoat.

Refer Product Data Sheet (TDS) for use and application guidelines.


The topcoat by design for Si-Prime penetrating primer, Si-Rex03 Silicone Resin Emulsion Paint (SREP) is a dynamic protective coating for concrete and masonry substrates with active water repellency, industry-leading breathability and proven durability and performance.


Klaas Coatings (North America) LLC
PO Box 25122
Dallas, TX 75225-1122

T: 866-317-3633 (toll free)
F: 214-363-8422


Markets We Supply

Transportation Infrastructure
Parking Structures
Office Buildings
Commercial and Retail
Warehousing and Distribution
Precast Concrete Fabricators
Historic Structures
Sport Complexes
Condominiums and Multi-Family
Tourism Infrastructure
Schools and Colleges

Technical Support

Looking for Application Guidelines?
Needing specification reference?



All orders supplied ex-factory – products not available through retailers.

Some regional building product distributors may carry, or order in, product as needed.

Product packaging
(packed volume by weight):

Si-Rex03 - 5 Gallon Pail or 55 Gallon Drum
Si-Prime - 5 Gallon Pail

Si-Rex03 orders are custom batch tinted at factory. Batch tinting ensures exact same color pail-to-pail. Minimum Order Quantities (MOQ) apply; contact for details.