Sika Sikalastic-590 IN
Single-component, water-based PU-modified acrylic liquid membrane that turns a leaking roof into a seamless, crack-bridging, solar-reflective waterproof skin.
What is it?
A one-component, water-based polyurethane-modified acrylic liquid-applied membrane from Sika, designed for exposed roof waterproofing with genuine cool-roof reflectivity.
Where is it used?
Exposed RCC roof slabs, terraces, parapets, and detailed roofs on residential, commercial, and institutional buildings across Delhi NCR and Pan-India.
Why use it?
It waterproofs and cools in one system: a seamless membrane that resists limited ponding, bridges hairline cracks, and reflects solar heat to cut cooling load.
How is it applied?
Brush, roller, or spray in a primer plus base and top coats, optionally reinforced with Sika Fabric-50 or Reemat Premium-225 over movement zones and details.
About Sika Sikalastic-590 IN
Sikalastic-590 IN is Sika’s answer to a problem every Indian building owner knows well: flat and low-slope roofs that leak at the joints, crack under thermal cycling, and bake in the summer sun. It is a single-component, ready-to-use liquid membrane built on a polyurethane-modified acrylic dispersion. You apply it cold, straight from the 20 kg pail, and it cures in air to form a seamless elastomeric skin bonded directly to the substrate. Because it is water-based, it is non-toxic, low-odour, and VOC-compliant, which makes it practical for occupied buildings, schools, and hospitals where solvent systems are hard to schedule.
What sets the 590 IN apart from a plain acrylic paint-grade coating is the combination of ponding tolerance, crack-bridging, and reflectivity in one product. The membrane withstands water standing on it for 72 hours without blistering or peeling, so the ordinary puddles that collect on a poorly-graded terrace after monsoon rain do not destroy it. It stays flexible enough to span the hairline movement cracks that open and close as a slab heats and cools. And in the White grade it carries a Solar Reflectance Index of 106, which pushes it firmly into cool-roof territory rather than merely claiming to be light in colour. For contractors and consultants, it is a single specification that covers refurbishment of a failing roof, life extension of an ageing one, and energy-efficiency upgrades on new construction.
The technical insight
The performance comes from the chemistry of the binder. A polyurethane-modified acrylic dispersion carries the elasticity and abrasion toughness associated with polyurethane while keeping the UV stability and water-based handling of acrylics. As the coating dries, water evaporates and the dispersed polymer particles coalesce into a continuous, cross-linked film rather than a brittle paint layer. That coalesced film is what delivers the roughly 300% elongation at break and around 50 Shore A hardness the datasheet reports: soft enough to stretch across a moving crack, firm enough to take foot traffic during maintenance. Adhesion of at least 1.5 N/mm2 to porous and non-porous substrates means the membrane grips concrete, old bitumen, and metal details without delaminating, so water cannot track sideways under the film the way it does beneath a poorly-bonded sheet. The acrylic component resists yellowing and weathering, which is why the white grade holds its reflectance instead of greying off within a season. Where cracks are wide or movement is significant, embedding Sika Fabric-50 or Reemat Premium-225 between coats turns the coating into a reinforced membrane, distributing strain across the mesh so the film is not asked to bridge a moving gap on its own.
Where it is used
- Waterproofing exposed RCC roof slabs and terraces on residential and commercial buildings
- Life-extension refurbishment of failing or ageing roof membranes without stripping the existing surface
- Reflective cool-roof coating (White grade) to lower internal temperatures and cooling costs
- Roofs with many penetrations, upstands, and complex geometry where sheet membranes are hard to detail
- Sealing parapets, gutters, and areas prone to limited water ponding
- Reinforced membrane build-up over cracks, joints, and seams using Sika Fabric-50 or Reemat Premium-225
- Waterproofing details around pipe penetrations, drains, and skylights with a thick-hair brush
- New-construction roof waterproofing where a seamless, UV-stable exposed system is specified
Key advantages
- Single-component and ready to use straight from the pail, so no on-site mixing errors or wasted part-B
- Genuine cool-roof reflectivity with a Solar Reflectance Index of 106 in the White grade
- Withstands limited ponding water for 72 hours without blistering or peeling
- Highly elastic with around 300% elongation, bridging hairline shrinkage and thermal cracks
- Seamless, fully-bonded finish with no laps, seams, or heat-welding to fail
- Water-based, non-toxic, low-odour and VOC-compliant, suitable for occupied buildings
- UV-resistant and resistant to yellowing, holding appearance and reflectance over time
- Excellent adhesion to both porous and non-porous substrates, and vapour-permeable so the slab can breathe
Limitations & considerations
- It is an exposed system and must not be overcoated with tiles, screed, or concrete
- Only two factory colours, White and Grey, so it is not a decorative multi-shade finish
- Application is limited to ambient and substrate temperatures of +10 C to +40 C and relative humidity up to 80%
- Substrate moisture must be below 6% by weight with no rising damp, so wet or green slabs must be dried and tested first
- Water-based curing slows sharply in cold or humid weather, extending overcoating and rain-resistance windows
- It tolerates limited ponding but is not a substitute for correct roof falls and functional drainage
Selection & best practice
Success with Sikalastic-590 IN is mostly about substrate discipline. Start with a sound, clean, laitance-free surface and confirm moisture is below 6% using a Tramex meter, CM measurement, or the oven-dry method, with an ASTM polyethylene-sheet check for rising damp. Prime with the 590 IN itself diluted 10% by weight with water and let it take up at roughly 0.3 kg/m2. Apply the base and top coats undiluted, mixing each pail for about a minute with a drill and paddle, and lay coats with a solvent-resistant short-piled lambskin roller to hold a consistent film thickness; use a thick-hair brush to work the material into all details and penetrations. Respect the overcoating windows, which are around 6 hours at +20 C and 4 hours at +30 C between unreinforced coats, and longer where mesh is embedded. Where the roof cracks, moves, or has irregular detailing, build a reinforced membrane by embedding Sika Fabric-50 or Reemat Premium-225 into a wet base coat before the top coat. Keep substrate and uncured material at least 3 C above dew point to avoid condensation, and plan around a full cure of roughly 4 days at +20 C or 2 days at +30 C before heavy service.
Specifications
| Chemical base | Polyurethane-modified acrylic dispersion (single-component, water-based) |
| Colours / Packaging | White or Grey; 20 kg container |
| Density | ~1.30 kg/L at +30 C (EN ISO 2811-1) |
| Solid content | ~60% by weight |
| Tensile strength | ~2.0 N/mm2 (free film, 14 days, +30 C, ASTM D412) |
| Elongation at break | ~300% (free film, 14 days, +30 C, ASTM D412) |
| Tensile adhesion strength | ≥1.5 N/mm2 (ASTM D4541) |
| Solar Reflectance Index | 106 (ASTM E1980-19), White grade |
| Curing at +30 C / 50% RH | Touch-dry ~1 h, rain-resistant ~6 h, fully cured ~2 days |
Industry use cases
Commercial and Institutional
Reflective White membrane over large office, mall, and hospital roof decks to waterproof and cut air-conditioning load in one specification.
Residential Terraces
Seamless waterproofing of exposed RCC terraces and parapets on homes and apartments where monsoon leaks and summer heat are both concerns.
Roof Refurbishment
Cost-efficient life extension of failing or ageing roofs, coating over sound existing surfaces without full demolition or stripping.
Complex-Detail Roofs
Plant rooms and roofs crowded with pipe penetrations, drains, and upstands, where a liquid system details far more reliably than sheet membranes.
Industrial and Warehouse
Reinforced build-up with Sika Fabric-50 or Reemat Premium-225 over large-span slabs subject to thermal movement and cracking.
Frequently asked questions
What is the coverage of Sikalastic-590 IN per square metre?
Can Sikalastic-590 IN take standing water?
Does it really work as a cool roof?
Can I tile or lay screed over it?
When do I need the reinforcement mesh?
How long before it is rain-safe and fully cured?
How we position Sika Sikalastic-590 IN
Sikalastic-590 IN sits in the middle of Sika’s liquid-roofing range: more robust and reflective than a basic acrylic coating, but water-based and cold-applied rather than a heavy PU system. Pair it with Sika Fabric-50 or Sika Reemat Premium-225 where reinforcement is needed, and specify Sika primers and detailing products from the same SikaRoof family for a warranted build-up. For a fully-bonded, higher-performance exposed roof where budget allows, Sika’s solvent-free PU liquid membranes step up from here. Within our wider portfolio, if the roof will be tiled or trafficked, look instead at a protected cementitious system such as Dr. Fixit or Fosroc crystalline and coating products; for below-grade or wet-area waterproofing, an MC-Bauchemie or Fosroc membrane is more appropriate than an exposed roof coating.
Fosroc Brushbond Roofguard — A specifier might choose Brushbond Roofguard when they want a fibre-reinforced acrylic elastomeric roof coating with built-in reinforcement in a single product, or where the project standardises on the Fosroc range.
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