Advanced acrylic base coat for asphalt roofing systems – engineered to lock in oils and prevent bleed-through
The GacoFlex A4271 Bleed Trap™ Base Coat is a high-performance, single-component, water-based acrylic sealer specifically formulated for use over roofing substrates containing bitumen. This includes Built-Up Roofing (BUR), all types of Modified Bitumen (APP and SBS), and smooth or granulated asphaltic roofing membranes. By encapsulating oils that naturally migrate from bituminous surfaces, A4271 creates a stable, sealed platform that effectively blocks these oils from seeping into subsequent roof coatings — a critical step in preserving the aesthetics, performance, and longevity of your silicone or acrylic topcoats.
Unlike generic primers or sealers, Bleed Trap™ is designed with specialised oil-blocking technology to address the unique challenges of asphalt-based roofing systems. Without a proper base coat, oil migration can cause unsightly staining, premature coating degradation, and warranty issues. The A4271 formulation ensures these issues are mitigated, helping installers achieve consistent, warrantable, and visually clean topcoat finishes.
This base coat is required for all Gaco warrantable applications over SBS-modified bitumen and is strongly recommended for APP-modified and smooth BUR systems, including mineral-surfaced cap sheets. While compatible with a wide range of substrates, it is not intended for use over gravel-surfaced BUR membranes.
£172.00 + VAT
Specialised Oil Encapsulation – Effectively locks in oils and prevents them from migrating to the surface, ensuring a clean and uniform finish for topcoats.
Enhanced Substrate Compatibility – Proven adhesion to MOD BIT, BUR, asphaltic membranes, galvanized steel, polyurethane foam, and concrete (adhesion testing advised on all single-ply membranes).
Performance-Driven Acrylic Film – Delivers excellent tensile strength, elongation, and tear resistance, creating a robust foundation for long-term waterproofing systems.
Low-VOC, Environmentally Compliant – Water-based formula with VOC content below 50 g/L for safer handling and compliance with environmental standards.
Warranty Compliance – Required under Gaco’s warranty programme for SBS substrates and recommended for other asphaltic surfaces to ensure full system eligibility.
User-Friendly Application – Easy to mix and apply using brush, roller, or spray, with excellent workability in a wide range of site conditions.
GacoFlex A4271 Bleed Trap™ Base Coat is ideal for protecting existing felt and asphalt roof covers from oil bleed through which can damage the appearance of the Gaco S42 Silicone Roof Coating:
Asphaltic Roof Preparation – Creates a stable, sealed surface ready for Gaco silicone or acrylic topcoats.
Warrantable Roof Systems – Essential underlayer for Gaco warrantable SBS-modified bitumen installations.
Surface Stabilisation – Reduces risk of coating discolouration or failure due to oil migration.
Compatibility Layer – Provides a bonding surface for coatings over challenging bituminous substrates.
Surface Preparation: Ensure surface is clean, completely dry, and free of loose granules, dust, grease, or biological growth. Do not pressure wash asphalt surfaces.
Mixing: Stir until homogeneous before use.
Application Temperature: 50°F to 110°F (10°C to 43°C).
Application Method: Roller, brush, or airless sprayer (2,000–3,000 psi, tip size 0.025–0.040 in).
Coverage Rate: 1 gallon per 100 sq. ft. (3.8 L per 9.3 m²) per coat. Maintain continuous 6 mil dry film thickness for effective bleed blocking.
Dry Time: Minimum 4 hours at 75°F (24°C) and 50% RH. Longer in cooler or more humid conditions.
Topcoating:
S4200 & GacoRoof (S1600): May be applied directly once A4271 is fully cured (adhesion test recommended).
Proper surface preparation is critical for achieving maximum adhesion, ensuring effective oil encapsulation, and securing the long-term performance of the GacoFlex A4271 BleedTrap™ Base Coat. Bituminous substrates, in particular, require thorough cleaning to ensure the coating bonds correctly and fully blocks oil migration.
1. Inspection
Assess the roof for cracks, blisters, loose material, or signs of water damage, and complete necessary repairs before coating.
Identify areas of heavy contamination such as grease, oil deposits, moss, or algae.
2. Cleaning with GacoWash
Clean all surfaces with GacoWash Concentrated Cleaner, diluted according to manufacturer’s instructions.
Apply with a low-pressure sprayer or brush, working the cleaner into the surface to loosen dirt, biological growth, and contaminants.
Allow the cleaner to dwell as directed, then thoroughly rinse off.
Do not pressure wash asphalt surfaces — use controlled rinsing to prevent moisture penetration into the substrate.
Areas with stubborn grease or contamination may require additional scrubbing or repeat cleaning.
3. Drying
Ensure the substrate is completely dry before applying A4271 BleedTrap™.
Avoid application after recent rainfall or during conditions of persistent high humidity.
4. Masking & Protection
Mask off areas not intended for coating, including roof edges, skylights, flashings, and adjacent walls.
Protect sensitive building materials, vehicles, and landscaping from overspray.
5. Adhesion Testing
Perform an adhesion test on all single-ply membranes and unfamiliar substrates.
Only proceed with full application once satisfactory adhesion results are confirmed.
The GacoFlex A4271 BleedTrap™ Base Coat is specifically formulated to work in direct combination with GacoFlex S42 High-Adhesion 100% Silicone Roof Coating. When applied over asphaltic substrates, A4271 encapsulates migrating oils, creating a clean, stable base that ensures S42 bonds seamlessly without the need for any additional primer.
Once A4271 has fully cured — typically a minimum of 4 hours at 75°F (24°C) and 50% RH — S42 can be applied directly. In cooler or humid conditions, allow extra curing time to ensure the base coat is completely dry before top coating.
This system is designed for maximum compatibility, delivering a uniform, bleed-free surface that enhances the appearance, durability, and long-term performance of the finished roof.
Safe handling of GacoFlex A4271 BleedTrap™ Base Coat is essential to protect applicators, building occupants, and the environment. Always read and follow the full Safety Data Sheet (SDS) before use.
1. Personal Protective Equipment (PPE)
Eye Protection: Wear safety glasses or chemical splash goggles.
Skin Protection: Use chemical-resistant gloves and protective clothing to avoid skin contact.
Respiratory Protection: When spraying or working in confined areas, use a properly fitted respirator suitable for water-based acrylic coatings.
Footwear: Wear safety footwear with slip-resistant soles when working on roof surfaces.
2. Work Area Safety
Ensure adequate ventilation during application and curing, particularly in enclosed or partially enclosed spaces.
Prevent access to the work area by untrained personnel during application.
Avoid working on wet, slippery, or unstable surfaces.
3. Safe Handling
Do not eat, drink, or smoke when handling the product.
Avoid breathing spray mist.
Wash hands, forearms, and any exposed skin thoroughly after handling.
4. Environmental Protection
Do not discharge product into drains, watercourses, or onto the ground.
Collect and dispose of waste material, empty containers, and wash water in accordance with local environmental regulations.
5. First Aid Measures
Eye Contact: Rinse cautiously with clean water for several minutes. Remove contact lenses if present and easy to do. Continue rinsing and seek medical advice if irritation persists.
Skin Contact: Wash with soap and water. Seek medical attention if irritation develops.
Inhalation: Move to fresh air and keep comfortable for breathing. Seek medical advice if symptoms persist.
Ingestion: Rinse mouth and do not induce vomiting. Seek medical attention immediately.
6. Fire Safety
Product has a flash point above 200°F (93°C) and is water-based; it is not classified as flammable.
In the event of a fire, use water spray, foam, dry chemical, or CO₂ to extinguish.
Available in: 19 litre pails
Shelf Life: 24 months in original, unopened containers when stored above freezing
Storage Conditions: Protect from freezing and excessive heat. Store in a dry, covered location.
Mixing: Stir thoroughly before each use to ensure a uniform product. Some separation may occur during extended storage — remix until homogenous.
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