Sika Sikalastic-510 CoolCoat IN
A single-component, water-based acrylic liquid membrane that waterproofs the roof and reflects solar heat in one seamless coat.
What is it?
A one-part, water-based acrylic liquid-applied membrane that cures into a seamless, elastic white or grey film for roofs and terraces.
Where is it used?
Exposed RCC roofs, factory and warehouse sheds, terraces, and complex roofs with many penetrations across hot Indian climates.
Why use it?
It does two jobs at once: it seals the slab against water and reflects solar radiation, with a Solar Reflectance Index of 101 or higher that pulls down surface temperatures.
How is it applied?
Brush, roller or airless spray in two coats over a clean, primed substrate at roughly 1.2 to 1.5 kg per square metre total.
About Sika Sikalastic-510 CoolCoat IN
Sikalastic-510 CoolCoat IN sits in Sika’s cool-roof range and answers a very Indian problem: flat terraces and metal-deck roofs that both leak during the monsoon and bake through the summer. It is a single-component product supplied ready to use from the pail, built on a modified acrylic dispersion that dries by simple water evaporation into a continuous, jointless elastomeric skin. Because the film is formed in place, there are no laps or seams to fail, and it moulds itself around parapets, drains, vent pipes and other awkward details that sheet systems struggle with.
What separates it from an ordinary acrylic paint is the pigment and binder system engineered for reflectance and durability. The white finish carries a Solar Reflectance Index of at least 101 measured to ASTM E-1980-19, so a large share of incoming solar energy is bounced back rather than soaked into the concrete. That keeps the slab cooler, eases the load on the space below, and slows the heat-driven ageing that cracks conventional coatings. Add UV stability, resistance to mould and fungus, and genuine vapour permeability, and you have a coating suited to both new construction and the refurbishment of tired, previously waterproofed roofs.
The technical insight
The performance comes from two mechanisms working together in one film. First, reflectance: the coating is loaded with high-albedo pigments that reject most of the solar spectrum, which is why the cured white membrane reports an SRI of 101 or more. A roof that reflects rather than absorbs simply does not reach the punishing surface temperatures that drive thermal cycling, so the substrate and the coating both age more slowly. Second, elasticity: the acrylic binder cures into a flexible film with a tensile strength around 2 N/mm2 and a Shore A hardness near 70, tough enough to walk on yet elastic enough to bridge shrinkage and thermal cracks up to about 2 mm wide. When the slab moves, the membrane stretches across the crack instead of tearing, so the waterproof seal survives the daily expansion and contraction that opens gaps in rigid coatings. Adhesion of at least 0.5 N/mm2 keeps that elastic film locked to the deck, and because it is vapour permeable, moisture trapped in the slab can escape rather than build pressure and blister the coating from beneath.
Where it is used
- Waterproofing and heat-reflecting exposed RCC terraces on residential and commercial buildings
- Cool-roof coating over factory, warehouse and industrial shed roofs to cut internal heat gain
- Refurbishment of ageing or previously waterproofed roofs without full removal
- Complex roofs with numerous penetrations, drains, parapets and upstands where seamless detailing matters
- External wall waterproofing on parapets and exposed vertical concrete surfaces
- Protective reflective coat over compatible cementitious or acrylic waterproofing systems
- New-build roof slabs where a single-coat waterproof-plus-reflective solution is specified
- Terraces and podiums needing a light-traffic, walkable protective finish
Key advantages
- Combines waterproofing and solar reflectance in one product, with an SRI of 101 or higher to ASTM E-1980-19
- Single-component and ready to use straight from the container, so no site mixing or ratio errors
- Seamless, jointless film that detants easily around pipes, drains and parapets without laps to fail
- Elastic membrane bridges cracks up to about 2 mm, absorbing thermal and shrinkage movement
- Water-based and low-VOC, making it safer to handle and low-odour on occupied buildings
- Vapour permeable, allowing the slab to breathe and reducing the risk of blistering
- UV, mould and fungus resistant for long service life on fully exposed roofs
- Suitable for both new construction and refurbishment, on concrete and compatible existing coatings
Limitations & considerations
- Not designed for permanently ponding water or immersion; free-standing water must drain away and full cure requires seven days before any ponding
- As a thin liquid membrane it is not a substitute for heavy-duty traffic decks or protected below-grade tanking
- Reflectance is highest with the white finish and will fall as the surface soils, so periodic cleaning is needed to retain cool-roof benefit
- Application demands correct surface preparation and priming; adhesion and film build suffer over dusty, damp or contaminated substrates
- Water-based curing is sensitive to weather, so it should not be applied when rain is imminent or outside the +5 to +40 degrees C window
- Substrate moisture above roughly 6 percent by weight and high humidity will slow or compromise film formation
Selection & best practice
Start with a sound, clean substrate: remove laitance, dust, oil and any failed coating, repair cracks and honeycombing, and make sure the roof drains with no dead ponding zones. Prime as recommended for the substrate and let the primer dry. Apply only when air and surface temperatures are between +5 and +40 degrees C, relative humidity is below about 80 percent, and substrate moisture is under roughly 6 percent by weight; never coat if rain is expected within a few hours. Lay the product in two coats to reach the full 1.2 to 1.5 kg per square metre, letting the first coat dry before the second and cross-laying the coats for even cover. Reinforce internal and external corners, drains, pipe collars and cracks with detailing so the weakest points get extra film. Expect light foot traffic in about 24 hours, but hold back any ponding or water testing for the full seven-day cure. Keep the containers sealed, store between +5 and +30 degrees C, and clean tools with water while the material is still wet.
Specifications
| Chemistry | Single-component, water-based modified acrylic dispersion |
| Colour | White or grey |
| Solar Reflectance Index (SRI) | Greater than or equal to 101 (ASTM E-1980-19) |
| Consumption | Approx. 1.2 to 1.5 kg/m2 applied in two coats |
| Density | Approx. 1.37 kg/L at +30 degrees C |
| Tensile strength | Approx. 2 N/mm2 |
| Tensile adhesion | Greater than or equal to 0.5 N/mm2 |
| Shore A hardness | Approx. 70 |
| Crack bridging | Up to 2 mm |
| Curing | Light traffic approx. 24 hours; full cure 7 days before ponding |
| Pack sizes | 5 kg and 25 kg containers |
Industry use cases
Industrial and Warehousing
Coating large factory and warehouse roofs to reflect solar heat, cut internal temperatures and reduce cooling load while keeping the deck watertight.
Commercial Buildings
Sealing and cooling exposed terraces and roof plant areas on offices, malls and institutions where a low-odour, water-based system suits occupied sites.
Residential Terraces
Renovating leaking or heat-soaked RCC terraces on homes and apartments with a single seamless membrane that both waterproofs and reflects.
Roof Refurbishment
Overcoating tired or previously waterproofed roofs with many penetrations, avoiding costly stripping while restoring both watertightness and reflectance.
Frequently asked questions
Does Sikalastic-510 CoolCoat IN both waterproof the roof and keep it cool?
How much material do I need per square metre?
Can it handle standing water on a flat terrace?
Do I need a primer, or can I coat the concrete directly?
White or grey, which should I choose for a cool roof?
Is it safe to apply on an occupied building?
How we position Sika Sikalastic-510 CoolCoat IN
Sikalastic-510 CoolCoat IN is the entry point in Sika’s cool-roof line for straightforward waterproof-plus-reflective work. Where a roof needs extra crack-bridging over an actively moving or micro-cracked substrate, step up to Sikalastic-520 Cool Coat Fibers IN, the fibre-reinforced version in the same family. Sika CoolCoat and its dedicated Sika CoolCoat Primer form the matched primer-and-topcoat reflective system, and for high-performance PU roof waterproofing Sikalastic-590 IN is the tougher liquid-applied option. From our wider portfolio, contractors chasing a cementitious reflective route often compare it with Dr. Fixit and MC-Bauchemie roof coatings, while Fosroc’s own Brushbond range covers the cementitious cool-coat alternative; our team can help you match the right chemistry to the substrate, exposure and budget on each project.
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