About STP ShaliUrethane LHM

ShaliUrethane LHM from STP Limited is a liquid-applied polyurethane waterproofing membrane built for structures that see standing water, thermal movement and constant weathering. Because it is a single-component system, there is no site mixing of resin and hardener and no pot-life clock to beat. The material is simply decanted and rolled or sprayed; it then cures by drawing moisture from the air, chemically knitting into one continuous rubber-like film with no overlaps, seams or heat-welded joints for water to track through. That seamless nature is its biggest practical advantage on Indian roofs, where parapets, drain mouths, pipe penetrations and planter kerbs make sheet systems slow and leak-prone.

For engineers and applicators, the appeal is the balance of high elongation and genuine durability. With elongation of around 700% and the ability to bridge substrate cracks, the cured membrane accommodates the daily expansion and contraction of concrete without splitting. It bonds tenaciously to concrete, screed, plaster and metal, resists water, mild acids and alkalis, and conforms to ASTM C-836 and ASTM C-898, the recognised standards for high-build elastomeric waterproofing. Space Arc supplies ShaliUrethane LHM and, as an applicator, installs it to the correct primer, film build and detailing specification so the membrane performs the way the datasheet promises.

The technical insight

The performance comes from the polyurethane chemistry and the way it cures. ShaliUrethane LHM is a moisture-triggered system: isocyanate groups in the resin react with ambient humidity and with the substrate to build a dense, cross-linked elastomer directly on the deck. Because that reaction happens in place, the membrane forms as one monolithic sheet rather than being assembled from strips, so there is no engineered weak point at a lap. The long, flexible polymer chains give the high elongation and low-temperature crack-bridging that let the film stretch over a moving crack and recover instead of tearing. High solids content means most of what is applied stays behind as cured film, so the specified two-coat, 1.5-2 mm build is achievable in practice. One honest consequence of the aromatic PU backbone is that direct UV exposure will darken or chalk the surface over time; this is cosmetic and does not compromise the waterproofing, but where appearance or UV life matters, an aliphatic PU or reflective top coat is added over it.

Where it is used

• Exposed RCC roof slabs and terraces subject to ponding and thermal cycling
• Balconies, chajjas and sunken wet areas in residential and commercial buildings
• Podium decks and terrace gardens beneath overburden, screed or planting
• Mechanical equipment rooms, plant decks and service floors
• Bridge decks, ramps and car-park decks where a monolithic membrane is preferred
• Water tanks, sumps and reservoirs after suitability confirmation for the exposure
• Detailing of parapets, upstands, drain mouths and pipe penetrations
• Refurbishment of leaking roofs where a cold, seamless overlay is required

Key advantages

• Single-component and ready to use, so no site mixing errors and no pot-life pressure
• Cures into a fully seamless, joint-free membrane with no laps to fail
• Very high elongation of about 700% with crack-bridging over moving cracks
• Cold-applied by roller or airless spray, with no flame or hot works on site
• Excellent adhesion to concrete, screed, plaster, metal and wood
• Stays elastic across a wide -20C to +80C service range
• Conforms to ASTM C-836 and ASTM C-898 for elastomeric waterproofing
• Follows complex geometry and detailing that sheet membranes handle poorly

Limitations & considerations

• The aromatic PU film yellows and chalks under direct UV, so an aliphatic or reflective top coat is advised where appearance or UV life matters
• Being moisture-cured, it needs a dry substrate at application; trapped or rising damp can blister the film
• Correct dry film thickness must be achieved over two coats, uneven or thin application reduces performance
• It is a membrane, not a structural or vapour-barrier substitute, and does not cure underlying structural cracks or drainage faults
• Curing and recoat times lengthen in cold or low-humidity conditions and shorten in hot weather, so timing must suit the ambient environment

Selection & best practice

Specifications

Industry use cases

How we position STP ShaliUrethane LHM

ShaliUrethane LHM sits in STP’s liquid polyurethane waterproofing family alongside the two-component ShaliUrethane LHM 2K, which suits projects wanting fast build and higher film in fewer passes, and STP’s ShaliPrime range of primers that must precede it for reliable adhesion. Where a UV-stable finish is required, pair it with an aliphatic PU top coat. Within our wider portfolio, specifiers comparing brands often weigh it against Dr. Fixit and MC-Bauchemie liquid PU systems for similar exposed-roof and podium duties; we can advise on the right fit for the substrate, exposure and budget rather than pushing a single line.

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