Polyurethane Sealants
Polyurethane Sealants Buyer's Guide — TradieCart
Polyurethane (PU) sealants are the go-to choice for construction and expansion joints where paintability, strong adhesion and durability matter. We stock PU sealants from Pasco, Durotech, Ardex, Sika, Tremco, Bostik, RLA, Mapei and Atech — covering everything from standard Class 25 joint sealants to high-movement facade products and fire-rated options.
Understanding PU Sealant Classifications
PU sealants are classified by movement class and modulus under ISO 11600:
- Movement Class 25 (+/-25%) — Standard for most construction joints. Suits expansion joints, window/door perimeters and precast panels.
- Movement Class 50 (+/-50%) — For high-movement facade joints, curtain walls and substrates with significant thermal expansion.
- Low Modulus (LM) — Softer and more flexible. Stretches without pulling away from substrates. Best for high-movement joints.
- Medium/High Modulus — Stiffer with higher tensile strength. Better for mechanically loaded or trafficable joints.
Key PU advantage over silicone: PU sealants are paintable. Key limitation: PU can yellow or chalk under prolonged UV — overpaint exposed joints or choose a product with enhanced UV resistance.
Popular Products
| Product | Best For |
|---|---|
| Pasco PascoFlex PU25 | The all-rounder — +/-25% movement, fast curing, paintable, mould resistant. 11 colours available. Ideal for expansion joints, precast panels, window/door frames and general construction sealing. |
| Ardex RA040 | Reliable Class 25 PU with 500% elongation and excellent primerless adhesion. Great for expansion joints, tilt-up panels and moving cracks. Grey and white. |
| Durotech Duroseal Hybrid 25C | Outstanding UV resistance and primerless adhesion. Low VOC, odourless, resistant to sea water and diluted acids. 10 colours. Best for exposed exterior joints needing long-term UV durability. |
| Durotech Duroseal 40FC | Medium modulus with wider temperature range (-30°C to +120°C). Suits mechanically loaded joints and environments with extreme temperature swings. |
| Pasco Firejoint PU | 4-hour fire rating, acoustic rated, UV stable. For fire-rated construction joints, pipe/cable penetrations and acoustic partitions. |
| Sika Sikaflex PRO | Low modulus, ISO 11600 F 25 LM certified, AS/NZS 4020 potable water approved. 11 colours. The go-to for spec-driven commercial projects. |
| Sika Sikaflex 11FC | Dual-purpose adhesive and sealant. Lower movement (+/-12.5%) but high bond strength. Best for bonding skirting boards, trims, acoustic tiles and light sealing. |
| Tremco Dymonic 100 | Best-in-class movement (+100/-50%), extreme UV resistance, can be applied to 24-hour-old concrete. Premium choice for high-performance facade and expansion joints. |
| Tremco TREMflex 50 | +/-50% movement with bubble-free cure in high heat and humidity — purpose-built for Australian conditions. Low modulus, fungus resistant. |
| Bostik Seal N Flex 1 P590 | +/-50% movement (Class A), low modulus, CSIRO long-term durability tested, made in Australia. Acoustic rated. Excellent for facade and precast panel joints. |
Coverage Guide (per 600ml Sausage)
Coverage depends on joint width and depth. Use the formula: linear metres = 600 ÷ (width mm × depth mm). This table applies to all 600ml PU sealants.
| Joint Width | 6mm Deep | 8mm Deep | 10mm Deep | 12mm Deep |
|---|---|---|---|---|
| 6mm | 16.6m | 12.6m | 10.0m | 8.4m |
| 8mm | 12.6m | 9.4m | 7.5m | 6.2m |
| 10mm | 10.0m | 7.6m | 6.0m | 5.0m |
| 12mm | 8.4m | 6.2m | 5.0m | 4.2m |
| 15mm | 5.7m | 5.0m | 4.0m | 3.3m |
| 20mm | 5.0m | 3.8m | 3.0m | 2.5m |
| 25mm | 4.0m | 3.0m | 2.0m | 1.9m |
Coverage is approximate. Actual yield may vary depending on joint profile, wastage and application method. Always use closed-cell polyethylene backing rod to control depth in joints wider than 10mm.
Quick Recommendation Guide
- Standard expansion/control joints → Pasco PascoFlex PU25 or Ardex RA040 — cost-effective, proven performers with +/-25% movement
- High-movement facade or curtain wall joints → Tremco TREMflex 50 or Bostik Seal N Flex 1 P590 — both offer +/-50% movement
- Maximum movement capability → Tremco Dymonic 100 — +100/-50% movement for the most demanding joints
- UV-exposed exterior joints → Durotech Duroseal Hybrid 25C — outstanding UV resistance without needing overpaint
- Fire-rated joints and penetrations → Pasco Firejoint PU — 4-hour fire rating, acoustic rated
- Bonding and sealing in one product → Sika Sikaflex 11FC — high bond strength adhesive/sealant
- Hot or humid conditions → Tremco TREMflex 50 — bubble-free cure designed for tropical Australian climates
Common Questions
How do I calculate how much sealant I need? — Measure the joint width and depth in millimetres, then divide 600 by (width × depth) to get linear metres per 600ml sausage. For example, a 15mm wide × 10mm deep joint gives 4.0 linear metres per sausage. Refer to the coverage table above for quick reference.
What is the difference between PU sealant and silicone? — PU sealants are paintable, have higher abrasion resistance and bond strongly to concrete and masonry without primer. Silicone offers better UV resistance and suits wet areas. For exterior construction joints that need painting, choose PU.
Do I need to prime before applying PU sealant? — Most PU sealants bond primerless to common construction substrates including concrete, masonry, brick and metal. Check the product TDS for specific substrate recommendations — some non-porous surfaces may need a primer.
Can PU sealant be left exposed to UV? — PU sealants can yellow or chalk under prolonged UV exposure. For exposed joints, either overpaint after curing or choose a product with enhanced UV resistance like Durotech Duroseal Hybrid 25C or Tremco Dymonic 100.
Should I use Pasco PU25 or Ardex RA040? — Both are excellent Class 25 general-purpose PU sealants. PU25 offers 11 colour options and is the most popular product in this category. RA040 has higher elongation (500%) and is a strong choice when colour range is not a priority.
When do I need a fire-rated PU sealant? — Use fire-rated PU sealants like Pasco Firejoint PU for joints in fire-rated walls, floors and ceilings, and around service penetrations (pipes, cables, ducts). These products are intumescent — they expand when exposed to fire to maintain the fire barrier.
Brands We Stock
We carry polyurethane sealants from Pasco, Durotech and Ardex as our preferred brands, alongside Sika, Tremco, Bostik, RLA, Mapei and Atech. Products are available in 300ml cartridges, 600ml sausages and box quantities for trade pricing. Same-day delivery available in Metro Melbourne.
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