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Use Silcor Primer BS for: Priming common dry construction substrates (<5% moisture) before applying Silcor polyurethane-based waterproofing membranes to ensure a strong, reliable bond.
Silcor Primer BS is a single-pack, fast-drying modified polyurethane primer, specifically formulated to optimise the adhesion of all Silcor® polyurethane-based membranes. Primer BS provides a strong physical bond to a wide variety of common construction substrates including concrete, masonry, compressed fibre cement sheet (CFC), metal, and brick. Its rapid drying time allows for quick project progression, often enabling membrane application shortly after priming. Silcor Primer BS is designed for substrates with a moisture content below 5% and even promotes adhesion in cold weather conditions.
Primer Information: This primer is exclusively for use under Silcor® polyurethane membranes. It is critical that the substrate moisture content is below 5%; testing with a calibrated moisture meter is essential before application. For substrates with moisture content between 5% and 10%, GCP recommends using Silcor® Primer BW Clear or EPOCOTE™ F100W Clear instead. Silcor Primer BS is supplied ready to use.
Cure Time: Silcor Primer BS dries quickly, typically becoming tack-free within 30 to 60 minutes at 20°C. It is crucial to apply the Silcor® polyurethane membrane within 24 hours after the primer becomes tack-free. If this window is missed, a specific reprime procedure can be followed up to 72 hours after initial application (see Application Information). After 72 hours, the primer must be mechanically removed.
Coverage Rate: The minimum application rate is 0.3 kg per square metre (or 0.3 litres/m²). A 17kg pail will cover approximately 56 square metres at this minimum rate for a single coat. Coverage may vary depending on substrate porosity and texture.
Application Temperature Range: While the TDS states it "promotes adhesion even in cold weather," no specific lower temperature limit is provided. Standard industry practice suggests applying primers and membranes above 10°C. Likewise, no upper limit or Relative Humidity (RH) limits are stated; adhere to best practice guidelines (e.g., apply below 35-40°C, ensure RH is <85%, and substrate temperature is >3°C above dew point).
Chemical Properties: A single-pack, modified polyurethane primer. While not explicitly stated as 'solvent-based', its fast drying time, use of Xylene for repriming preparation, and storage advice (keep from ignition sources) strongly suggest the presence of solvents. Assume appropriate VOC precautions are necessary. The cured primer is water-resistant, offering temporary protection if rain interrupts work after it has become tack-free but before membrane application (within the coating window).
Key Features of Silcor Primer BS
- Fast Drying: Becomes tack-free in approximately 30-60 minutes at 20°C, allowing for rapid progress and potential same-day membrane application.
- Strong Adhesion: Creates a robust physical bond between the substrate and Silcor polyurethane membranes, crucial for system performance and longevity.
- Wide Substrate Compatibility: Suitable for priming a broad range of common rigid construction materials including concrete, masonry, CFC sheet, metal, and brick (ensure MC <5%).
- Single-Pack Convenience: Ready to use directly from the container, no mixing required, simplifying site work.
- Cold Weather Performance: Formulated to promote adhesion even in cooler conditions (observe practical temperature limits).
- Defined Reprime Window: Offers a specific procedure using Xylene to potentially salvage primed areas if the initial 24-hour coating window is missed (up to 72 hours).
Why Choose Silcor Primer BS:
- Optimise Silcor PU Membrane Bond: Ensures reliable adhesion specifically for GCP's polyurethane membranes, fulfilling system requirements.
- Speed Up Application Cycles: The quick drying time helps meet project deadlines by reducing waiting periods before membrane installation.
- Versatile Application: Use confidently across multiple common substrates found on typical Australian building sites (when dry).
- User-Friendly: Simple application by brush, roller, or spray with no complex mixing involved.
- Reliable System Component: Backed by GCP Applied Technologies for use within specified Silcor systems.
When to Choose Silcor Primer BS versus Alternatives:
- Choose Silcor Primer BS when: You are applying a Silcor *polyurethane* membrane AND the substrate is one of the listed compatible materials (concrete, masonry, CFC, metal, brick) AND the substrate moisture content is confirmed to be less than 5%.
- Choose Silcor Primer BW Clear / EPOCOTE F100W Clear when: The substrate moisture content is between 5% and 10%.
- Consider Silcor Primer BS 117 when: You are applying a Silcor *polyurea* or *hybrid polyurea* membrane (BS is for PU membranes only) OR when specific high-performance characteristics of BS 117 (like higher adhesion values, specified environmental controls) are required by the project specification (remember BS 117 also requires <5% MC).
- Do Not Use Silcor Primer BS when: Substrate moisture is above 5%, or when applying non-polyurethane membranes.
Trade-Specific Applications for Silcor Primer BS:
For Waterproofing Applicators:
- Application: Priming internal wet areas (bathrooms, laundries), external above-ground areas (balconies, non-trafficable roofs), retaining walls (positive side), and planter boxes prior to applying Silcor polyurethane membranes.
- Material Compatibility: Versatile across concrete, render, CFC sheeting, blockwork, and brick substrates typically encountered in these areas. Ensure <5% MC.
- Performance Benefits: Fast drying speeds up multi-step processes. Reliable bond ensures compliance with AS 3740 and AS 4654.2 when used as part of a full system.
For Builders and General Contractors:
- Application: Convenient primer for preparing various substrates before subcontractor application of Silcor PU membranes, or for direct application in smaller jobs. Suitable for pre-cast panels, in-situ concrete, masonry walls, and CFC linings.
- Technique: Straightforward application via roller or brush. Key focus must be on thorough surface preparation and confirming substrate dryness (<5% MC).
- Performance Benefits: Simplifies primer choice due to broad substrate compatibility. Fast drying aids overall project scheduling.
For Remedial Waterproofers:
- Application: Priming prepared surfaces after removal of old membranes or coatings, prior to installing new Silcor PU membrane systems on balconies, rooftops, or wet areas.
- Material Compatibility: Adheres well to correctly prepared aged concrete, masonry, and other compatible substrates common in remedial work. Substrate assessment for soundness and dryness (<5% MC) is crucial.
- Performance Benefits: Provides a reliable bonding bridge for the new membrane system. Fast drying helps minimise disruption during remedial projects.
Application Information
- Required Tools: Brush, roller (quality non-shedding), or airless spray equipment. Moisture meter (calibrated). Cleaning supplies (cloths, vacuum). Xylene (for reprime procedure). Appropriate PPE.
- Trade-Specific Tips: *All Trades:* ALWAYS test substrate moisture content before priming (<5% required). Prepare surfaces diligently. Apply primer evenly, avoiding pooling. Plan work to ensure membrane application within 24 hours of primer being tack-free. *Applicators:* Note the specific reprime procedure (Xylene wipe, dry, light reprime coat) if the 24hr window is missed but less than 72hrs have passed.
- Common Issues and Solutions: *Poor Adhesion:* Usually due to substrate moisture >5%, inadequate surface preparation (dust, contaminants), or exceeding the coating window (24hrs without reprime, or >72hrs). Requires removal/remediation. *Primer Dries Too Slowly:* Likely due to cold temperatures or high humidity; allow more time, ensure conditions are suitable. *Primer Dries Too Fast:* High temperatures; work in smaller manageable sections.
Storage and Shelf Life
- Storage Requirements: Store pails sealed in a cool, dry area, protected from direct sunlight and moisture. Keep away from all sources of ignition, sparks, open flames, and foodstuffs, as product is likely flammable.
- Shelf Life Information: 12 months from date of manufacture when stored unopened in recommended conditions. Check pail for manufacture date and use stock rotation (first-in, first-out).
- Handling Considerations: Assumed flammable - exercise caution. Ensure good ventilation during use. Keep containers sealed when not in use. Refer to Safety Data Sheet (SDS).
Certifications and Compliance
- Silcor Primer BS is a component designed for use within waterproofing systems intended to meet the requirements of the National Construction Code (NCC) and relevant Australian Standards like AS 4654.2 (Waterproofing membranes for external above-ground use) and AS 3740 (Waterproofing of domestic wet areas).
- Compliance is achieved when used as part of a complete, correctly installed GCP system according to the project specification and relevant standards.
- Project-specific warranties may be available from GCP and recognised contractors, often dependent on system design and application rates.
Frequently Asked Questions About Silcor Primer BS
Q: What is the main difference between Silcor Primer BS and Silcor Primer BS 117?
A: Silcor Primer BS is specifically for use under Silcor *polyurethane* (PU) membranes and has broad substrate compatibility. Silcor Primer BS 117 is primarily for Silcor *polyurea* and *hybrid polyurea* systems (though can be used for PU too), has higher tested adhesion values, lower viscosity, but stricter specified environmental controls and a different reprime procedure.
Q: My concrete moisture reading is 7%. Can I still use Silcor Primer BS?
A: No. Silcor Primer BS requires the substrate moisture content to be a maximum of 5%. For moisture levels between 5% and 10%, GCP recommends using Silcor Primer BW Clear or EPOCOTE F100W Clear. Applying Primer BS over 5% MC will likely lead to adhesion failure.
Q: How cold can it be when I apply Silcor Primer BS? The datasheet mentions cold weather.
A: The datasheet states it promotes adhesion in cold weather but doesn't give a specific minimum temperature. Standard industry best practice is generally to apply primers and membranes above 10°C ambient and substrate temperature. While it might perform better than some primers below this, applying in very cold conditions risks slow drying and potential dew point issues.
Q: I primed yesterday morning but couldn't apply the membrane. It's now been 30 hours. What do I do?
A: You have missed the initial 24-hour window but are within the 72-hour limit. You need to follow the reprime procedure: Wipe the primed surface thoroughly with Xylene solvent. Allow the Xylene to completely evaporate (surface is dry). Then apply a light coat of Silcor Primer BS (approx 0.15 kg/m²). Allow this to become tack-free before applying the membrane.
Q: Is Silcor Primer BS flammable? What safety gear is essential?
A: While not explicitly stated as flammable in the excerpt, the storage advice (keep from ignition sources) and use of Xylene in repriming strongly suggests it contains flammable solvents. Assume it is flammable. Essential PPE includes solvent-resistant gloves and eye protection. Good ventilation is crucial. Respiratory protection (organic vapour respirator) is highly recommended, especially indoors or if spraying.
Q: Can I use Silcor Primer BS under a Silcor polyurea membrane like Silcor 900MP?
A: No, Silcor Primer BS is specified for use with Silcor *polyurethane-based* membranes. For Silcor polyurea or hybrid polyurea systems, the recommended primer is typically Silcor Primer BS 117 (or other specified primer based on substrate/conditions). Always use the primer specified for your chosen membrane system.
Use Silcor Primer BS for:
- General Waterproofing Priming: Reliable priming for internal wet areas (bathrooms, laundries) under Silcor PU membranes, adhering to AS 3740 requirements when part of a system.
- External Above-Ground Areas: Priming balconies, podiums (non-trafficable), and retaining walls before Silcor PU membrane application, contributing to AS 4654.2 compliance.
- Priming CFC Sheeting: Effectively priming compressed fibre cement sheets often used in wet areas and facades prior to liquid PU membrane application.
- Concrete & Masonry Preparation: Ensuring good adhesion of Silcor PU membranes to various concrete finishes (in-situ, precast, render) and masonry/brickwork, provided surfaces are dry (<5% MC).
- Metal Surface Priming: Preparing correctly cleaned and profiled metal components for subsequent Silcor PU membrane coating.
Why Use Silcor Primer BS for:
- Reliable PU System Adhesion: Provides the crucial bond specifically tailored for Silcor polyurethane membranes across a wide range of common building substrates found in Australia.
- Faster Project Turnaround: The quick 30-60 minute drying time (at 20°C) allows waterproofing contractors to proceed quickly to membrane application, saving time on site.
- Versatility on Dry Surfaces: Simplifies primer choice for projects involving multiple dry substrates like concrete, CFC, masonry, metal, or brick under a Silcor PU membrane.
- Ease of Application: As a single-pack product requiring no mixing, it's straightforward for builders and applicators to use correctly with standard tools (roller/brush/spray).
- Defined Process for Delays: The specific reprime procedure offers a practical solution if minor delays push work beyond the initial 24-hour window, potentially saving costly removal work if addressed before 72 hours.
How to apply Silcor Primer BS:
- Check Substrate Moisture: Using a calibrated moisture meter, confirm the substrate moisture content is less than 5%. Do not proceed if moisture is higher.
- Prepare Substrate: Ensure the surface is structurally sound, smooth, clean, and dry. Remove all dust, laitance, grease, curing compounds, or other contaminants by appropriate means (grinding, pressure washing, vacuuming etc.).
- Complete Detailing: Ensure all required detailing (e.g., joints, fillets, penetrations) according to NCC/AS standards and membrane system specification is completed *before* priming.
- Apply Primer: Apply one coat of Silcor Primer BS directly from the container using a brush, roller, or spray equipment at a minimum rate of 0.3 kg/m². Apply evenly and avoid pooling.
- Allow to Dry: Let the primer coating become tack-free. This typically takes 30-60 minutes at 20°C but varies with temperature and humidity.
- Apply Membrane (within 24 hrs): Apply the selected Silcor polyurethane waterproofing membrane strictly according to its Product Data Sheet instructions *within 24 hours* of the primer becoming tack-free.
- Reprime Procedure (If 24-72 hrs): If the membrane cannot be applied within 24 hours, but less than 72 hours have passed since priming, wipe the surface with Xylene, allow it to dry completely, then apply a light repriming coat of Silcor Primer BS (approx. 0.15 kg/m²). Allow this to become tack-free before applying the membrane.
- Removal (If >72 hrs): If the primed area is not coated with membrane within 72 hours, the primer must be fully removed by mechanical means (e.g., diamond grinding) back to the bare substrate, and the surface must be re-primed starting from Step 4.
Silcor Primer BS limitations:
- Dry Substrates Only: Absolutely critical - cannot be applied to substrates with moisture content of 5% or higher. Use Silcor Primer BW Clear / EPOCOTE F100W Clear for 5-10% MC range.
- Polyurethane Membranes Only: Specifically designed for use under Silcor *polyurethane-based* membranes. Not specified for polyurea or other membrane chemistries.
- Coating Window: Membrane must be applied within 24 hours for optimal results. A specific reprime procedure is required between 24 and 72 hours. Full removal necessary after 72 hours.
- Environmental Conditions: While claiming cold weather performance, application should follow best practice regarding temperature (likely >10°C), humidity (likely <85% RH), and dew point (substrate >3°C above DP).
- Assumed Flammable/Solvent Content: Requires careful handling regarding ignition sources and necessitates good ventilation and appropriate PPE due to likely solvent content.
Safety precautions when using Silcor Primer BS:
- Personal Protective Equipment (PPE): Wear solvent-resistant gloves (e.g., nitrile), safety glasses or goggles. Protective clothing recommended.
- Ventilation: Ensure good fresh air ventilation during application and drying, especially in enclosed spaces. Mechanical ventilation may be required.
- Respiratory Protection: Due to likely solvent content and application methods (especially spraying), respiratory protection (e.g., half-mask respirator with organic vapour cartridges) is recommended. Consult SDS and AS/NZS 1715/1716.
- Ignition Sources: Assume product is flammable. Keep away from sparks, open flames, excessive heat, and non-explosion-proof electrical equipment. No smoking.
- Handling: Avoid skin and eye contact. Wash hands after use. Keep container sealed when not stored.
- First Aid & SDS: Read and understand the Safety Data Sheet (SDS) before use for detailed information on hazards, handling, emergency procedures, and first aid.
- Disposal: Dispose of leftover primer and contaminated waste according to local environmental regulations. Do not empty into drains or waterways.
Silcor Primer BS can be used on the following substrates:
- Concrete: In-situ slabs/toppings, off-form, shotcrete, pre-cast panels, light-weight foamed concrete. Must be structurally sound, minimum 25 MPa strength, cured (min 14-28 days), clean, and dry (<5% MC).
- Masonry: Brickwork, blockwork. Must be sound, clean, dry (<5% MC), and free from efflorescence.
- Cement Render: Fully cured, sound, clean, and dry (<5% MC).
- Compressed Fibre Cement Sheet (CFC): Common sheeting used in wet areas and external cladding. Must be clean, dry (<5% MC), and firmly fixed.
- Metal: Ferrous and non-ferrous metals. Must be clean, free of rust/corrosion/oils, and preferably mechanically abraded or prepared according to membrane system specification to provide a key. Must be dry (<5% MC).
- Important Note: Substrate moisture content MUST be below 5%. Verify with a moisture meter before priming.
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