About STP ShaliCryl LM

STP’s ShaliCryl LM is the workhorse acrylic coating that many Delhi-NCR contractors reach for when a terrace has to be both dry and cool. It arrives ready to use in a single pail, no site mixing of powder and liquid, no pot-life clock ticking, so a crew can prime in the morning and lay coats through the day. Once cured it forms a continuous, rubbery film that moves with the slab, bridging the hairline and shrinkage cracks that inevitably open up on Indian rooftops through the summer-monsoon-winter cycle. Because it is micro-fibre reinforced, the membrane carries more tensile and tear strength than a plain acrylic emulsion, which is why STP rates it as a heavy-duty coating able to take normal foot traffic without a separate protective screed.

The second half of the ShaliCryl LM story is heat. The white grade is engineered as a cool-roof coating with a Solar Reflective Index around 105 and solar reflectance of 0.82, so it throws back a large share of incoming radiation instead of letting it soak into the slab below. For an owner, that means a measurably cooler top floor and lower air-conditioning load, on top of a leak-free roof. The three-colour build sequence is not cosmetic, it is a quality-control tool, the changing colour tells the applicator that each coat is complete and that the specified consumption, and therefore the specified thickness, has actually been achieved. That combination of waterproofing, thermal comfort and built-in QA is what makes it a mainstay of exposed-roof specifications.

The technical insight

The performance comes from three things working together. First, the acrylic polymer cures into an elastomer with elongation at break around 300%, so as the concrete expands, contracts and cracks, the film stretches across the gap rather than tearing, verified crack-bridging is up to 1.0 mm over ten thermal cycles. Second, the dispersed micro-fibres act like rebar in miniature, lifting tensile strength to about 1.7 N/mm² and resisting the tear propagation that normally starts at a crack tip, which is why it survives structural movement where an unreinforced coating would split. Third, the pigmentation and binder are tuned for radiative cooling, high reflectance and high emittance (0.92) let the surface both reject sunlight and shed absorbed heat, while the film stays breathable (water-vapour transmission around 21 g/m²/24h) so trapped moisture can escape instead of blistering the coating from underneath. The result is a membrane that is simultaneously watertight, elastic and heat-rejecting, and that stays that way after 1000 hours of accelerated UV with no hardening or chalking.

Where it is used

• Waterproofing exposed flat and sloped RCC roofs and terraces subject to light foot traffic
• Overlaying and rejuvenating old brick-bat coba and cementitious screed treatments
• Coating complex geometry, domes, arches, shell and paraboloid roofs, and steep flashings where sheet membranes cannot conform
• Sealing parapet walls, chajjas, gutters and channels against driven rain
• Crack repair and surface waterproofing of vertical wall faces in cementitious substrates
• Cool-roof application where a high-SRI white finish is required to cut heat gain
• Re-coating over existing acrylic coatings and concrete screeds as a maintenance layer
• Waterproofing balconies, terrace gardens and podium areas over sound substrates

Key advantages

• Single-component and ready to use, no on-site powder-liquid mixing and no pot-life pressure
• High solar reflectance (SRI ~105, reflectance 0.82) delivers genuine cool-roof and energy-saving benefit
• Micro-fibre reinforcement gives high tensile strength (~1.7 N/mm²) and tear resistance
• Elastic, resilient film with ~300% elongation bridges cracks up to 1.0 mm and absorbs structural movement
• Three-colour coat sequence provides built-in visual QA for correct thickness and consumption
• Seamless, monolithic finish conforms to complicated shapes that sheet membranes cannot
• Water-based, low-odour and non-polluting, with resistance to fungal, yeast and mould growth
• Withstands normal foot traffic without a separate protective screed, and bonds strongly to concrete and metal

Limitations & considerations

• Not a structural or pressure-side membrane, it is a surface coating and cannot resist negative water pressure or standing water
• Cannot be applied over damp substrates or during rain, the surface must be fully dry with no oil, grease, mill scale or rust
• Bitumen-based treatments must be completely removed by mechanical scarification before application, it does not bond over them
• UV/cool-roof benefit depends on a white top coat, coloured finishes reduce reflectance and STP suggests ShaliCryl LM HI as top coat for best SRI
• Under-application below the specified consumption gives thin, under-performing film, the coloured coats must be built to the rated thickness
• Elastomeric acrylic film is best kept to light foot traffic, it is not a wearing surface for vehicles or heavy movement

Selection & best practice

Specifications

Industry use cases

How we position STP ShaliCryl LM

Within the STP range, ShaliCryl LM is the standard high-SRI acrylic membrane, where the coolest possible roof is the priority, STP recommends finishing with ShaliCryl LM HI as the top coat for an even higher Solar Reflective Index. It pairs naturally with the STP repair family that the system itself calls for, ShaliFix FRM 90 for repairing damaged brick-bat coba, PlastiSeal for filling surface cracks, and Shalimar Dam-It for treating blisters, all used during surface preparation. Where a specifier prefers a rigid cementitious pressure-tolerant system for wet areas and sunken slabs rather than an exposed elastomeric roof coating, our Fosroc waterproofing range, including polymer-modified cementitious coatings, is the alternative to consider.

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