STP ShaliUrethane LHM 2K
A two-component, 100% solids polyurethane liquid membrane that cures into a seamless, high-tensile waterproofing skin for roofs, decks and wet areas.
What is it?
A two-part (base + hardener) aromatic polyurethane that is mixed on site and applied cold as a liquid, curing to a joint-free elastomeric membrane at 100% solids.
Where is it used?
Terraces, podium and car-park decks, sunken toilets and balconies, water tanks and other concrete surfaces needing a tough, monolithic waterproof layer.
Why use it?
The chemical cure gives faster strength gain and better mechanical properties than moisture-cured 1K systems, so it handles foot traffic and mild chemical exposure without a fabric reinforcement in most cases.
How is it applied?
Prime the prepared substrate with ShaliPrime, then power-mix Part A and Part B and apply two coats at 720 g/m2 each by brush, roller or airless spray, allowing the first coat to firm up before the second.
About STP ShaliUrethane LHM 2K
STP ShaliUrethane LHM 2K is the two-component member of STP Limited’s ShaliUrethane liquid-membrane family. Where the single-pack LHM relies on ambient humidity to cure, the 2K grade carries its own isocyanate hardener in Part B. Once Part A and Part B are combined, the reaction proceeds on its own timetable rather than waiting on the weather, which is why site teams reach for it during monsoon windows, in cold conditions, and on jobs where the deck has to be handed back quickly. The result is a 100% solids film with no solvent to flash off, so the applied thickness is the built thickness.
For contractors and consultants in Delhi NCR and across India, the appeal is a predictable, seamless membrane that terminates cleanly around drains, upstands and penetrations where sheet systems usually fail. Space Arc Engineering supplies LHM 2K as an authorised STP distributor and applicator, which means the material arrives with the correct primer, the batch is matched to the area being covered, and the crew that lays it understands STP’s coving, priming and recoat discipline. That combination of verified product and trained application is what separates a membrane that lasts a decade from one that debonds in two monsoons.
The technical insight
The performance comes from how the film is built rather than how it dries. Because Part B supplies the curing agent, the polyurethane crosslinks by reacting with itself instead of drawing moisture from the air, so a full-thickness coat gains strength uniformly top to bottom and does not skin over and trap uncured material underneath. At 100% solids there is no solvent evaporation, so a 720 g/m2 coat stays close to 0.7 mm of real membrane, and two coats build the continuous barrier that stops water tracking sideways to a defect. The cured film is deliberately elastomeric, stretching well beyond 300% before it tears, which lets it span shrinkage cracks and ride the daily thermal movement of an exposed slab without splitting. Adhesion to a primed concrete deck is high enough that even if water reaches a pinhole it cannot migrate under the film, and the ShaliPrime layer keeps residual substrate moisture from undermining that bond.
Where it is used
- Terrace and rooftop waterproofing on new and existing RCC slabs
- Podium decks and landscaped areas over occupied space
- Multi-level and basement car-park decks that must reopen to traffic quickly
- Sunken portions of toilets, bathrooms and utility areas
- Balconies, chajjas and planter boxes exposed to standing water
- Water storage tanks and reservoirs (with the appropriate potable-grade check)
- Fast-track and monsoon-season jobs where a moisture-cured 1K would cure too slowly
- Cold-weather waterproofing where ambient humidity alone is unreliable
Key advantages
- Chemical cure gives faster strength gain than moisture-cured 1K PU, shortening the reopening time
- 100% solids means the coat you apply is the thickness you keep, with no solvent shrinkage
- Seamless, joint-free film with no laps or welds to fail at drains and upstands
- High elongation lets the membrane bridge shrinkage cracks and absorb thermal movement
- Strong adhesion to primed concrete resists water creep beneath the film
- Handles foot traffic and mild acid or alkali exposure once fully cured
- Applies by brush, roller or airless spray, so it suits both small wet areas and large decks
- Backed by ASTM C-836 and ASTM C-898 for liquid-applied roofing membranes
Limitations & considerations
- Aromatic PU is not colour-stable in sunlight; exposed decks yellow or chalk unless protected with a UV-stable aliphatic topcoat, tiles or a screed
- Two-component mixing must be accurate and power-mixed; hand-stirring or wrong ratios leave soft, uncured patches
- Pot life is limited (about an hour), so only mix what the crew can lay in that window
- Substrate moisture must be controlled (broadly under 5%); applying over a wet or green slab risks blistering and debonding
- The product is flammable before cure and needs ventilation and PPE, keeping it away from open flames
- Trafficked and podium areas still need a protection screed or wear coat over the membrane
Selection & best practice
Start with a sound, cured slab: grind off laitance, oil and old coatings, cut and fill cracks, and form 75 mm coving at all wall junctions with polymer-modified mortar. Confirm the surface is dry (well below 5% moisture) before priming with ShaliPrime WB or PUM and letting it go tacky. Mix the full Part A and Part B packs together with a slow-speed paddle (around 100 RPM) until uniform, never a partial pack by eye, and use the batch within its pot life. Lay the first coat at 720 g/m2, let it firm to a tack-free state, then apply the second coat at the same rate, ideally cross-hatched to the first for even build. On weak or cracked substrates, or at movement joints, embed a non-woven geotextile in the first coat with overlaps. Protect the finished membrane before it takes service load, and add a UV-stable topcoat or screed anywhere it stays sun-exposed. Coordinate the primer, membrane and topcoat as one STP system rather than mixing brands.
Specifications
| Product type | Two-component, cold-applied polyurethane liquid membrane (aromatic, 100% solids) |
| Cure mechanism | Chemical cure via Part A + Part B reaction |
| Elongation at break | 500 ± 50% (ASTM D412) |
| Tensile strength | 1.25 ± 0.20 MPa (ASTM D412) |
| Adhesion to primed concrete | 2 ± 0.5 MPa (ASTM D4541) |
| Coverage | ~720 g/m2 per coat, 2 coats (approx. 1.44 kg/m2 total) |
| Pot life / recoat | Pot life 60 ± 10 min; recoat 8-12 hr; trafficable 36-48 hr |
| Standards | ASTM C-836 and ASTM C-898 |
| Pack size / shelf life | 26 kg unit (25 kg A : 1 kg B); 9 months sealed, stored 5-38 C |
Industry use cases
Commercial rooftops
Large office and mall terraces get a seamless membrane that terminates cleanly around the many drains, vents and AC plinths that break up a commercial roof.
Multi-level car parks
The fast chemical cure lets a deck bay be primed, coated and returned to traffic on a tight schedule, with a protection wear coat over the membrane.
Residential wet areas
Sunken toilets, bathrooms and balconies are sealed as a continuous film that wraps up the coving, eliminating the joints where tiled wet areas usually leak.
Water-retaining structures
Tanks and reservoirs benefit from a tough, crack-bridging lining that resists constant water contact and mild chemical exposure.
Podium and landscaped decks
Over occupied space, the elastomeric membrane rides structural movement and is buried under insulation, screed or planting for long-term protection.
Frequently asked questions
What is the difference between ShaliUrethane LHM and LHM 2K?
How much LHM 2K do I need per square metre?
Is ShaliUrethane LHM 2K UV-stable for exposed terraces?
What primer and surface prep does it need?
How long before the deck can take traffic?
Can Space Arc supply and apply it in Delhi NCR and elsewhere in India?
How we position STP ShaliUrethane LHM 2K
ShaliUrethane LHM 2K sits at the workhorse centre of STP’s liquid-membrane range. Where a job is exposed and needs a lasting colour-stable finish, pair it with or step up to an aliphatic UV-resistant grade such as ShaliUrethane LM UV 2K as a topcoat, and reach for the single-pack ShaliUrethane LHM when a simpler moisture-cured membrane is enough. Always specify it as a system with ShaliPrime WB or PUM as the primer, ShaliCrete-modified mortar for coving and crack repair, and ShaliProtek or a screed for protection over trafficked decks. Across our other brands, comparable 2K PU liquid membranes include Fosroc’s Nitoproof line, Dr. Fixit’s Roofseal / Torchshield PU membranes and Sika’s Sikalastic range, so consultants who have standardised on those specifications can be matched to an equivalent without changing the detailing.
Fosroc Nitoproof PU2000 — Specify the Fosroc two-component PU when the membrane is buried below grade in aggressive soil and tanking performance, rather than an exposed or trafficked deck finish, is the priority.
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