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Waterproofing horizontal surfaces often forces a choice: build for robust concealment or for long-term exposure. Silcor 575 LB removes that dilemma. It delivers certified, high-performance waterproofing for both concealed horizontal areas and, when paired with Silcor Top Coat 75, provides a UV-stable and light foot trafficable finish. This single product simplifies specification and on-site logistics for critical horizontal applications.
Silcor 575 LB is a one-part, high solids, polyurethane membrane developed for straightforward, cold application on horizontal substrates with falls. It cures via ambient humidity, forming a tough, flexible, and seamless elastomeric membrane. The formulation allows it to semi self-level, creating a smooth finish that is crucial for robust waterproofing in both non-exposed and, when overcoated with Silcor Top Coat 75, exposed horizontal areas.
Silcor 575 LB is applied cold with a roller or brush in two cross-directional coats. Substrates must be primed first with a compatible GCP primer, such as Silcor Primer BS for dry conditions or Epocote F100W for damp or green concrete. The membrane becomes tack-free in around four hours at 23°C/60% RH, with recoat possible after 12 hours. Full through-cure takes 48 hours, at which point it is ready for flood testing or topping. Clean application equipment immediately with xylene solvent.
Silcor 575 LB is typically applied after detailing and priming, forming the primary waterproofing layer on horizontal surfaces. It requires a compatible GCP primer like Silcor Primer BS or Epocote F100W, selected based on substrate moisture conditions. For critical detailing, Silcor LM PU Sealant is used to form bond breaker fillets in internal corners and around penetrations, ensuring flexibility at stress points. Once cured, the membrane's protection strategy depends on the final finish: it can be covered by screeds with a tie coat (using an additional layer of Silcor 575 LB and blinded with aggregate), protected by Protectoboard or Rapid-Drain for backfilled or unbonded screed applications, or exposed to UV and light foot traffic when overcoated with Silcor Top Coat 75.
While both Silcor 575 LB and Silcor 560 HB Low VOC are one-part, cold-applied polyurethane membranes from GCP, they are designed for different primary applications. Silcor 575 LB is specifically formulated for horizontal substrates, offering semi self-levelling properties that result in a smooth finish. This makes it ideal for areas like balconies and podiums where a high-quality aesthetic is desired, and crucially, it can be exposed to UV and light foot traffic when overcoated with Silcor Top Coat 75. In contrast, Silcor 560 HB Low VOC is a thixotropic (non-sag) membrane. This characteristic makes it more suited for vertical applications and detailing, but it must always be concealed as it is not UV stable. Choose Silcor 575 LB when your project requires a seamless, self-levelling horizontal membrane that offers the option of an exposed finish; opt for Silcor 560 HB Low VOC when a non-sag, concealed membrane is needed for vertical or detailed work.
Yes, it is certified Class III to AS 4654.1-2012 for external non-exposed applications and AS/NZS 4858-2004 for internal wet areas. This confirms its suitability for compliant installations.
SILCOR 575 LB can be used on exposed horizontal areas if overcoated with SILCOR Top Coat 75. This topcoat provides UV stability and protection for foot traffic.
No, it is not suitable for heavy duty foot or vehicle trafficable applications, even with a protective top coat. Its use is limited to areas with light foot traffic when protected by SILCOR Top Coat 75, or non-trafficable applications.
Apply when substrate and ambient temperatures are between +5°C and +35°C, with relative humidity between 35% and 85%. Do not apply if rain is imminent or the dew point is less than 3°C below the substrate temperature.
| Application | Key benefit | Primary trades |
|---|---|---|
| Balconies, podiums, and roof decks | Achieves compliant Class III waterproofing (AS 4654.1-2012) for non-exposed external horizontal areas, ensuring long-term protection under toppings. | Waterproofers, Builders, Architects |
| Green roofs and landscaped decks | Provides a monolithic, high extensibility (800%+ elongation) membrane that accommodates structural movement and bridges non-structural cracks under soil loads. | Landscapers, Waterproofers |
| Plant room floors and bunds | Forms a seamless, fully bonded polyurethane layer resistant to water, bleach, and detergents (AS 4858), containing spills effectively. | Industrial Builders, Waterproofers |
| Internal wet area floors (under or over screeds) | Certified Class III to AS/NZS 4858-2004, offering reliable internal waterproofing for bathrooms and laundries, preventing water ingress into sub-structures. | Tilers, Waterproofers, Plumbers |
Substrate must be sound (min 20 MPa), smooth, clean, and dry. Remove all dust, laitance, oil, curing compounds, and contaminants by grinding, shot blasting, or high-pressure water blasting. Repair all defects.
All detailing must be done *before* priming.
Install a bond breaker fillet of SILCOR LM PU Sealant (min. 12x12mm internal, 15x15mm external). Allow to cure for 12 hours.
Chase non-moving joints/cracks, prime, and fill with SILCOR LM PU Sealant over a bond breaker tape. For movement joints, consult your GCP representative.
Prime all substrates with the appropriate GCP primer. Apply membrane within the primer's recoat window.
Mix pail thoroughly with a drill (max 600 RPM). Apply membrane using a 10-14mm nap roller in two (or more) cross-directional coats to achieve the specified DFT (e.g., 1.5mm total).
If direct-sticking tiles or applying bonded screeds, a tie-coat is **mandatory**. Between 12-48 hours of the final membrane coat, apply a fresh coat of SILCOR 575 LB at 0.95 kg/m². Immediately broadcast to refusal (120% coverage) with 0.5-1.0mm clean, dry quartz sand. Allow 24h cure, then vacuum off excess sand.
Signal Word: Danger
Wear protective gloves (rubber or nitrile rubber), safety glasses with side shields, and appropriate protective clothing. Use respiratory protection if exposure limits are exceeded or in inadequately ventilated areas.
Use only outdoors or in a well-ventilated area. Ensure good interior ventilation, especially at floor level, as fumes are heavier than air.
Store in original packaging between 15°C and 25°C, under cover, protected from heat, ignition, moisture, frost, and direct sunlight. Shelf life is nine months. Dispose of contents and containers according to local regulations. Do not allow product to reach sewage systems.
Proper substrate preparation and priming are critical for the long-term performance of the SILCOR 575 LB membrane. Incorrect preparation can lead to adhesion failure or pin-holing.
Surface prep: Substrates must be structurally sound, dry, and clean, with a minimum compressive strength of 20 MPa. Remove all dirt, dust, curing compounds, and contaminants. Rectify porous surfaces or defects with an appropriate repair mortar. Chase construction joints to 10mm x 10mm and static cracks greater than 1.0mm to 6mm x 6mm.
Primer: Required. For moisture content below 5.0%, use SILCOR Primer BS or EPOCOTE F100W Clear. For moisture content between 5.0% and 6.9%, only use EPOCOTE F100W Clear. Prime when substrate temperature is stable or falling to minimise outgassing.
Surface prep: Ensure sheets are installed to manufacturer's specifications, clean, dry, and free from sealers or coatings.
Primer: Required. Use SILCOR Primer BS for optimal penetration and adhesion on CCS flooring substrates. EPOCOTE F100W Clear can also be used.
Surface prep: Remove corrosion, oxides, oil, and grease. Roughen the surface by abrasion or garnet blasting to SA 2.5 (near white metal). Solvent wipe with xylene or MEK.
Primer: Required. Prime within 30 minutes of preparation using EPOCOTE F100W Clear or SILCOR Primer BS. For stainless steel, copper, or aluminium, use Dow Chemical DOWSIL 1200 OS Primer.
| Property | Value |
|---|---|
| Membrane Chemistry | High solids, moisture curing polyurethane |
| Appearance | Grey viscous liquid |
| Specific Gravity | 1.40 g/ml |
| Brookfield Viscosity | 7,000 mPa.s |
| Solids Content | 91 %w/w |
| VOC | <110 g/L |
| Tack Free Time (23°C/60% RH) | 4 hours |
| Gel Time (23°C/60% RH) | 6 hours |
| Min Recoat Time (23°C/60% RH) | 12 hours |
| Max Recoat Time (23°C/60% RH) | 48 hours |
| Min Through Cure Time (23°C/60% RH) | 48 hours |
| Rain Resistant Min Cure (23°C/60% RH) | 2 hours |
| Ready for Flood Testing/Topping (23°C/60% RH) | 48 hours |
| Shore A Hardness | > 65 °A |
| Tensile Strength | > 4.5 MPa (AS 4858), > 5.0 MPa (AS 4654.1) |
| Elongation | > 900 % (AS 4858), > 800 % (AS 4654.1) |
| Classification | Class III High Extensibility (AS 4858-2004, AS 4654.1-2012) |
| Resistance to Cyclic Movement | Pass (No fatigue cracking exhibited) |
| Bond Strength to Primed Concrete | >48 N (AS 4654.1) |
| Water Vapour Transmission Rate | 4.87 g/m²/24h |
| Resistance to Water Immersion | Pass |
| Resistance to Bleach Immersion | Pass |
| Resistance to Detergent Immersion | Pass |
| Resistance to Heat Ageing | Pass |
| Application Temperature Range (Substrate/Ambient) | +5°C to +35°C |
| Application Relative Humidity Range | 35% to 85% |
| Minimum Dry Film Thickness (General) | 1.5 mm |
| Shelf Life | 9 months |
Here are some common examples on where Silcor 575 used by our customers.
