Sika Sikalastic-450 (I)
A single-component, aliphatic polyurethane liquid membrane that cures with atmospheric moisture into a seamless, UV-stable, crack-bridging waterproof film for exposed roofs and concrete.
What is it?
A ready-to-use, single-component aliphatic polyurethane liquid-applied waterproofing coating that cures with air moisture into a seamless elastomeric membrane.
Where is it used?
Non-trafficked RCC roofs, inverted roofs, podium decks, retaining walls before backfill, and refurbishment overlays on old asphalt or corrugated roofing.
Why use it?
Its aliphatic chemistry resists yellowing, chalking and UV degradation, so an exposed roof stays protected for years without a sacrificial top coat.
How is it applied?
Prime the substrate with a 50% water-diluted coat, then apply two full coats by brush, roller or airless spray to build a continuous membrane.
About Sika Sikalastic-450 (I)
Sikalastic-450 (I) is Sika’s single-component, aliphatic polyurethane liquid-applied waterproofing coating, engineered for concrete surfaces and roofs that stay permanently exposed to sun and weather. It arrives ready to use in the pail: no mixing of parts, no fiddly ratios. Once spread, it reacts with the humidity already in the air and cures into a tough, rubbery, fully bonded film that has no joints or overlaps for water to find. Because the membrane is monolithic and adheres directly to the deck, any leak that does start cannot travel underneath it the way it can beneath a loose-laid sheet.
What sets this grade apart is the aliphatic backbone of the polymer. Ordinary aromatic polyurethanes darken, chalk and go brittle under Indian sunlight within a season or two; an aliphatic PU holds its colour and its flexibility, which is why Sikalastic-450 (I) is specified for the top, sacrificial layer on roofs and podiums rather than buried applications alone. The cured film bridges shrinkage and thermal cracks, shrugs off abrasion and light foot traffic during maintenance, resists mild acids and general industrial pollution, and carries root-resistance when built up as part of a landscaped roof system. It is not, however, a tanking product: Sika does not rate it for permanent water immersion, so tanks, pools and water-retaining structures need a different solution.
The technical insight
The performance comes from two design choices working together: moisture-triggered curing and aliphatic chemistry. As a one-component PU, the resin carries reactive isocyanate groups that stay dormant in the sealed pail and only begin to crosslink when they meet water vapour in the air. That reaction knits the coating into a continuous three-dimensional elastomer with no cold joints, which is why coverage and film build matter more than any mixing skill. The aliphatic (straight-chain) structure of the polymer is the reason it survives sunlight: aliphatic PUs do not carry the light-absorbing aromatic rings that cause aromatic grades to yellow, chalk and embrittle, so the film keeps its elasticity and crack-bridging ability through years of UV exposure. That elasticity is what lets the membrane stretch across a moving crack instead of tearing over it, passing the 3 mm mandrel crack-bridging test while remaining fully bonded to the substrate.
Where it is used
- Waterproofing of non-trafficked RCC and concrete roof slabs exposed to weather
- Inverted (protected-membrane) roofs and podium decks
- Retaining walls and below-grade concrete faces coated before backfilling
- Refurbishment overlays on aged asphalt, bituminous felt or corrugated metal roofs
- Protective, seamless coating for infrastructure concrete in polluted or mild-acid environments
- Terraces and roofs feeding into a landscaped / green-roof build-up requiring root resistance
- Sheds and factory roofs where a UV-stable, brushable membrane is preferred over sheet systems
- Repair and re-coating of previously waterproofed exposed surfaces without full tear-off
Key advantages
- Single-component and ready to use, eliminating on-site mixing errors and part-ratio waste
- Aliphatic chemistry gives genuine UV and weathering stability with minimal yellowing over time
- Cures to a seamless, fully bonded film with no joints or laps that water can undermine
- Excellent crack-bridging elasticity, passing the 3 mm mandrel test over moving substrates
- Bonds directly to concrete, brickwork, asphalt and corrugated sheet substrates
- Applied by brush, roller or airless spray, so awkward details and large areas are both manageable
- Resistant to abrasion, hydrolysis, mild acids and general industrial pollution
- Root-resistant when incorporated into a built-up landscaped roof system
Limitations & considerations
- Not suitable for permanent water immersion, so it cannot waterproof tanks, pools or water-retaining structures
- Rated for non-trafficked surfaces; regular foot or vehicle traffic needs a separate wearing / protection layer
- Moisture-cure means very low humidity slows curing while damp or wet substrates trap moisture and cause defects
- Substrate must be sound, clean and dry (typically 6% or less residual moisture) with a primer coat first
- Single-pack PU is moisture-sensitive in storage; opened or part-used pails skin over and have limited pot life
- Correct wet film build across two coats is essential, as thin or uneven application compromises the membrane
Selection & best practice
Success with Sikalastic-450 (I) is mostly about substrate discipline and film build. Make sure the concrete is fully cured, structurally sound, free of laitance, oil and dust, and dry to roughly 6% moisture or less; grind or scabble smooth or contaminated areas and fill honeycombs and blowholes beforehand. Round off all internal corners with a fillet and treat cracks, drains and upstands as detail points. Stir the pail thoroughly to a homogeneous consistency, then apply a priming coat of the material diluted about 50% with clean water at roughly 0.25 kg/m2 and let it cure (typically 2 to 4 hours depending on weather). Follow with two full coats, allowing the first to set before the second, and always apply the second coat at right angles to the first to eliminate pinholes and guarantee continuous coverage. Work within the recommended air and substrate temperature window, avoid application when rain is imminent or the surface is damp, and protect the fresh membrane from water and traffic until it has cured. Allow the full cure period (up to about 7 days, faster in warm weather) before the roof is put back into service.
Specifications
| Type | Single-component, aliphatic elastomeric polyurethane, liquid-applied |
| Cure mechanism | Moisture (air) cure |
| Colour | Black (liquid and cured film) |
| Pack size | 20 kg container |
| Primer coat | Product diluted ~50% with clean water, approx. 0.25 kg/m² (cures in 2–4 hrs) |
| Coats & consumption | Two full coats over primer; approx. 0.50 kg/m² per coat |
| Crack bridging | Passes 3 mm mandrel test |
| Full cure | Up to ~7 days, depending on temperature and humidity |
| Storage | Sealed original packaging, dry, between +5°C and +30°C |
Industry use cases
Commercial & residential roofs
Exposed RCC terraces and roof slabs that need a seamless, UV-durable membrane without the laps and seams of sheet systems.
Podiums & inverted roofs
Podium decks and protected-membrane roofs where the coating waterproofs beneath insulation, ballast or a landscaped build-up.
Infrastructure & industrial
Protective waterproof coating for infrastructure concrete and factory roofs in polluted or mild-acid atmospheres.
Retaining structures
Below-grade retaining walls and concrete faces coated on the positive side before backfilling.
Roof refurbishment
Overlay on aged asphalt, felt or corrugated roofing to restore watertightness without a full strip-out.
Frequently asked questions
Can Sikalastic-450 (I) be used inside water tanks or swimming pools?
Why choose the aliphatic (I) grade over a cheaper aromatic PU coating?
How much material do I need and in how many coats?
Can it take foot traffic once cured?
What condition does the substrate need to be in before coating?
How is it applied and how long before it is fully cured?
How we position Sika Sikalastic-450 (I)
Within Sika’s own liquid-membrane family, step up to Sikalastic-560 or a Sikalastic reinforced system when you need a thicker, longer-warranty exposed roof build-up, and pair with Sika primers plus SikaFlex or Sikadur crack and joint sealants at detailing points such as drains, upstands and expansion joints. For permanent water immersion — tanks, pools and water-retaining structures that this grade explicitly rules out — move to a cementitious crystalline or two-component flexible system rather than a PU coating. Across our other brands we can offer comparable liquid-applied and cementitious waterproofing from Dr. Fixit and MC-Bauchemie where a project or approved-vendor list calls for them, and we help specifiers match the right chemistry to the exposure rather than defaulting to one product.
Fosroc Brushbond RFX — Where a specifier wants a two-component acrylic polymer-modified cementitious coating — easier over damp substrates and usable on the negative face — Brushbond RFX is the natural Fosroc alternative, though it lacks the aliphatic UV stability of an exposed PU membrane like Sikalastic-450 (I).
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