Sika Sikalastic-853 R AP
Two-component, hot spray-applied hybrid polyurea membrane that cures in seconds to form a seamless, crack-bridging waterproofing skin on roofs and decks.
What is it?
A 2-part, hot spray-applied hybrid polyurea membrane that gels in about 20 seconds to give a seamless, fully bonded waterproofing layer roughly 1.5 to 2.0 mm thick.
Where is it used?
Exposed and protected flat or sloping roofs, balcony and terrace decks, podiums, pedestrian decks, stadium seating and concrete or metal deck protection.
Why use it?
It bridges cracks, has no laps or joints, and is rain-resistant within about 5 minutes, so large roofs are watertight in a single fast-track shift.
How is it applied?
Sprayed by trained applicators through heated, high-pressure plural-component equipment onto a primed substrate, followed by an aliphatic top coat where UV-exposed.
About Sika Sikalastic-853 R AP
Sikalastic-853 R AP belongs to Sika’s family of liquid-applied roofing membranes, but it behaves quite differently from a brush or roller coating. It is supplied as two reactive components, an isocyanate (Part A) and a polyol blend (Part B), mixed one-to-one by volume through a heated spray gun, with a Part C toner included to set the colour. The instant the two streams meet on the substrate they react and gel in roughly 20 seconds, building a continuous elastomeric film that owes its speed and toughness to polyurea chemistry rather than to solvent leaving the film. Because it is near-100% solids with very low VOC, almost everything sprayed stays on the roof as membrane, and there is no shrinkage or off-gassing as it cures.
For engineers and contractors in India, the appeal is throughput and reliability on large or awkward roofs. A seamless spray membrane removes the overlaps, welds and detailing failures that dog sheet systems, and the material wraps upstands, drains, penetrations and complex geometry as one monolithic skin. It is rain-resistant in about 5 minutes at +25°C, so a shower shortly after application does not ruin the day’s work. Where the roof stays fully exposed to sunlight, Sikalastic-853 R AP is over-coated with a Sika aliphatic top coat to hold colour and resist UV; where it is buried under ballast, paving or tiles on a terrace or podium, it works as the concealed waterproofing layer on its own.
The technical insight
The performance comes from the polyurea reaction itself. Isocyanate and polyol react by chemical addition, not by evaporation, so cure does not depend on ambient drying and the film can be built to full thickness in one pass. That reaction is extremely fast, which is why gel time is measured in seconds and why the material must be atomised through heated, high-pressure plural-component equipment that meters and mixes the two parts precisely at the gun tip. The heat, with Part A near 55°C and Part B near 66°C, lowers viscosity for clean atomisation and consistent stoichiometry. The cured membrane reaches about 10 N/mm² tensile strength, roughly 58 N/mm tear strength and around 79 Shore A hardness after 7 days at +23°C, giving a tough yet elastic skin that stretches to accommodate thermal movement and bridges shrinkage cracks in the deck instead of splitting over them. That combination of instant set, seamless build and crack-bridging elasticity is what lets a roof be waterproofed and back in service within hours rather than days.
Where it is used
- Fast-track waterproofing of exposed flat and sloping concrete roofs, finished with a Sika aliphatic top coat for UV stability
- Concealed waterproofing of balcony and terrace decks beneath ballast, paving slabs or tiles
- Podium decks and pedestrian decks carrying foot traffic and protective finishes
- Stadium seating floors and tiered concrete structures with complex geometry
- Protection and waterproofing of metal roof decks and profiled steel
- Refurbishment of ageing roofs where a seamless overlay is preferred to stripping and re-sheeting
- Detailing of upstands, gutters, drains and penetrations as part of a monolithic membrane
- Large-area industrial and commercial roofs where single-shift turnaround matters
Key advantages
- Gels in around 20 seconds and is rain-resistant in about 5 minutes, allowing very fast return to service
- Seamless, fully bonded membrane with no laps, welds or joints to fail
- Bridges cracks and stays elastic, accommodating thermal and structural movement in the deck
- Near-100% solids with very low VOC, so almost no shrinkage and minimal odour
- High mechanical strength, roughly 10 N/mm² tensile and 79 Shore A, for durability under foot and weather
- Conforms to JIS A 6021, giving a recognised performance benchmark for specification
- Wraps complex details, upstands and penetrations as one continuous skin
- Single-pass build to 1.5 to 2.0 mm thickness reduces the number of application stages
Limitations & considerations
- Requires heated, high-pressure plural-component spray equipment and trained applicators; it is not a brush or roller product
- On fully UV-exposed roofs it must be over-coated with a Sika aliphatic top coat to retain colour and resist yellowing
- Very short gel time leaves no room to rework the wet film, so surface preparation and equipment calibration must be right first time
- Application is limited to substrate temperatures of +5°C to +35°C, relative humidity up to 85% and substrate moisture not exceeding 4%
- Correct priming of the concrete or metal substrate is essential for adhesion and to avoid pinholing over damp or porous decks
- Supplied only in large drum packs (200 kg, 175 kg and 15 kg), which suits sizeable projects rather than small patch repairs
Selection & best practice
Success with Sikalastic-853 R AP is largely decided before the gun is switched on. Confirm the substrate is sound, clean and dry, with moisture content not exceeding 4% by weight, then apply the appropriate Sika primer for concrete or metal so the membrane bonds and does not pinhole. Only work within the stated window of +5°C to +35°C and relative humidity up to 85%, and check the dew point so condensation does not form on a cool deck. Set the plural-component machine so Part A runs near 55°C and Part B near 66°C, verify the 1:1 mix ratio, and purge and test-spray before starting the roof. Build the base coat to about 2.00 kg/m² for a finished thickness of roughly 1.5 to 2.0 mm, keeping a wet edge and paying close attention to upstands, drains and penetrations. Where the roof will stay exposed, follow with the aliphatic top coat at about 0.2 kg/m² once the base has set. Store the drums unopened between +5°C and +30°C, and because the chemistry and equipment are unforgiving, restrict application to experienced, Sika-trained spray crews.
Specifications
| Product type | Two-component, hot spray-applied hybrid polyurea roof waterproofing membrane |
| Mix ratio | Part A : Part B = 1:1 by volume (Part C toner supplied) |
| Solids / VOC | Near-100% solids content with very low VOC |
| Density | Approx. 1.01 kg/L |
| Gel time | Approx. 20 seconds at +25°C |
| Rain resistance | Approx. 5 minutes at +25°C |
| Tensile strength / Shore A | ~10 N/mm² tensile, ~58 N/mm tear, ~79 Shore A (7 days at +23°C) |
| Coverage | Base coat ~2.00 kg/m²; aliphatic top coat ~0.2 kg/m²; finished thickness ~1.5-2.0 mm |
| Standard / Packaging | Conforms to JIS A 6021; Part A 200 kg drum, Part B 175 kg drum, Part C 15 kg |
Industry use cases
Commercial and industrial roofing
Waterproofing large exposed concrete roofs in a single fast-track shift, over-coated with an aliphatic top coat for long-term UV stability.
Residential terraces and balconies
Concealed membrane under tiles, paving or ballast on terrace and balcony decks where a seamless, crack-bridging layer prevents seepage into slabs below.
Podiums and car parks
Durable, trafficable waterproofing for podium decks and pedestrian areas that must handle movement, foot traffic and protective finishes.
Stadiums and public infrastructure
Monolithic waterproofing of stadium seating floors and stepped concrete structures where complex geometry rules out sheet membranes.
Roof refurbishment
Seamless spray overlay on ageing or failing roofs, avoiding the cost and disruption of stripping and re-sheeting the existing deck.
Frequently asked questions
Is Sikalastic-853 R AP a brush or roller coating?
Does it need a top coat?
How fast can the roof be back in service?
What thickness and coverage should I plan for?
What are the substrate and weather limits for application?
How is it supplied and to what standard does it conform?
How we position Sika Sikalastic-853 R AP
Sikalastic-853 R AP is the fast-track, spray-applied choice within Sika’s roofing range. Where a project needs a liquid membrane that can be brush or roller applied by a general crew rather than a specialist spray team, Sika’s Sikalastic single-component liquid membranes are the more practical route, and Sika primers should be specified to suit the concrete or metal substrate ahead of the base coat. As an authorised distributor, Space Arc can also pair this membrane with joint sealants and repair mortars from Sika and our other principals to complete the roof detailing package. Across brands, buyers weighing a spray polyurea roof will often also look at Fosroc’s spray-applied polyurea systems for a directly comparable option.
Fosroc Polyurea WPE — A specifier may prefer Fosroc’s spray-applied two-component polyurea when the job leans toward tanking, water-retaining structures or corrosion protection and very high elongation matters more than a roof-specific hybrid formulation.
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