Primer for elastomeric polyurethane and polyurea membranes

Product Description

A fast-drying, single-pack, modified polyurethane primer for use with all polyurethane and polyurea based membranes.


  • Strong physical bond to substrate
  • Fast-drying PU resin system
  • Coating is water-resistant and protects the structure in the event of interruption by wet weather
  • Promotes adhesion even in cold weather


SILCOR® Primer BS is used for all SILCOR® polyurethane and polyurea membrane and BITUTHENE® Mastic Membrane.
It may be applied to most rigid substrates used in construction including: concrete masonry, off-form concrete, in-situ concrete slabs and topping, shotcrete and cement render, light-weight foamed concrete, pre-cast concrete panels, compressed fibre cement sheet, metal and brick.


Substrates must be structurally sound, smooth, clean and dry. Remove all dust, laitance, loose matter, oil, curing compound, form release agents, or other contaminants.
Concrete should be cured 28 days and render 7 days.
SILCOR® Primer BS is used for substrates with maximum moisture content of 5%.


Apply one coat directly from container using brush, roller or spray. While still wet, sand broadcast with washed, cleaned, oven dried silica quatz sand size 0.3mm to 0.6mm into the primer if delay between priming and membrane application of more than 24 hours is expected. (Optional)
Allow primer coating to become tack-free before applying waterproof membrane. Only apply primer to substrate that will be membrane coated within 6 hours. 
Apply the selected polyurethane and polyurea waterproofing product from GCP Applied Technologies in strict accordance with product instructions.

Typical Properties

Property Typical Value
Colour Clear
Specific Gravity 0.9-1.0g / mL
Adhesion to concrete substrate, ASTM D4541 >1.5MPa
Water Resistance Excellent
Drying Time @ 20°C 20 - 30 minutes
SILCOR® PRIMER BS is flammable - exercise care when using in a confined space. Use PPE and/or ventilation as appropriate, if required. 
Any primed area not coated with membrane within 6 hours must be first wiped with Xylene. As soon as xylene has dried, reprime with a light coat of SILCOR® PRIMER BS at a rate of approximately 0.1kg / m2. Any applied primer that has not been coated with membrane within 72 hours of application, must be fully removed by diamond grinding and re-primed.


Application rate is approx 0.15kg / m2 (0.15L / m2); 0.3kg / m2 or more may be required for very porous concrete.


SILCOR® Primer BS is packed in 17kg metal pails.

Clean Up

Use xylene before cured. Exercise care and review all Safety Data Sheet (SDS) before use.


Store in a cool, dry place. Unopened cans have a shelf life of 12 months at 25ºC, 60% RH. Keep away from any fire hazards or ignition sources.

Health and Safety

In case of spills and accidents, refer to the SDS of the products or when in doubt contact your local GCP representative.
Always wear protective clothing, gloves and protective goggles when handling chemical products.
For full information, consult the relevant SDS. | For technical information:

We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate, and is offered for consideration, investigation and verification by the user, but we do not warrant the results to be obtained. Please read all statements, recommendations, and suggestions in conjunction with our conditions of sale, which apply to all goods supplied by us. No statement, recommendation, or suggestion is intended for any use that would infringe any patent, copyright, or other third party right.

SILCOR and BITUTHENE are trademarks, which may be registered in the United States and/or other countries, of GCP Applied Technologies, Inc. This trademark list has been compiled using available published information as of the publication date and may not accurately reflect current trademark ownership or status.

© Copyright 2021 GCP Applied Technologies, Inc. All rights reserved.

GCP Applied Technologies Inc., 2325 Lakeview Parkway, Alpharetta, GA 30009, USA
GCP Vietnam Company Ltd, Lot B14, Section B, Street No. 12, Xuan Thoi Son Small Scale Arts & Crafts Group, National Road 22Xuan Thoi Son Village, Hoc Mon District, Ho Chi Minh City
This document is only current as of the last updated date stated below and is valid only for use in Vietnam. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2023-06-12