STP SuperThermoLay APP
A five-layer, APP-modified bituminous membrane built for the heat: torch-bonded waterproofing that holds its shape on exposed Indian roofs where softening point and UV resistance actually decide service life.
What is it?
A prefabricated, torch-applied waterproofing membrane made from APP (atactic polypropylene) modified bitumen, reinforced with a non-woven polyester mat and available in 2, 3, 4 and 5 mm thicknesses.
Where is it used?
Exposed and protected roof slabs, terraces, podiums, underground car parks, bridges, tunnels, roof gardens and swimming pools.
Why use it?
Its high softening point (>=150 C) resists flow and slump on sun-baked terraces, while the polyester core carries structural movement without splitting.
How is it applied?
Rolled over a primed, cured substrate and flame-bonded with an LPG torch until the surface embossing melts, with 100 mm end laps and 75 mm side laps sealed by extruded bitumen bead.
About STP SuperThermoLay APP
SuperThermoLay APP from STP Limited is a torch-on bituminous membrane engineered for the reality of Indian rooftops, where summer deck temperatures routinely push conventional bitumen past its limit. The membrane is a five-layer system: a spun-bonded non-woven polyester reinforcement weighing 140 g/m2 sandwiched between layers of APP-modified bitumen, with a thermo-fusible polyethylene film on the torch face. The atactic polypropylene modification is what raises the softening point above 150 C, so the compound stays dimensionally stable and resists flow even under prolonged direct solar exposure. That single property is why specifiers reach for an APP grade over unmodified felt on exposed terraces.
For contractors and consultants, the practical appeal is a fully factory-controlled thickness and a bond that is instant once the torch passes. There is no curing wait as with liquid systems, and no site mixing to get wrong. The polyester core gives the sheet real tensile strength and elongation, letting it bridge shrinkage cracks and accommodate thermal movement of the slab below. STP supplies it in plain finish (PE film both faces) for protected build-ups and in a mineral or natural grey slate finish for exposed applications that need a built-in UV-stable wearing surface. It carries ASTM D 5147 and IS 16532:2017, the current Indian standard for polymer-modified bitumen membranes, which matters when a membrane has to clear a third-party spec on a government or institutional job.
The technical insight
The performance hinges on the polymer. Plain oxidised bitumen behaves like a thermoplastic that softens and creeps as temperature climbs, which is exactly the failure mode on a flat, exposed terrace in Delhi or the plains. Blending atactic polypropylene into the bitumen builds a semi-crystalline polymer network that lifts the softening point to >=150 C and gives “no flow” behaviour when held at 120 C for two hours (IS 13826 Part 5). In practice that means the membrane does not slump at parapets or run at overlaps through peak summer. The non-woven polyester mat is the second half of the story: unlike glass fibre, polyester stretches, so the sheet records elongation of roughly 40 percent in the heavier grades while still carrying 650 N/5 cm longitudinal tensile strength. That combination, high heat stability from the APP and high strain capacity from the polyester, is what lets one torched layer take up slab movement and thermal cycling for years rather than cracking at the first stress line.
Where it is used
- Exposed terrace and flat-roof waterproofing on domestic, commercial and industrial buildings
- Protected roofing under screed, tiles or paver finishes as a single-layer system
- Podium decks and landscaped roof gardens over habitable space
- Underground car parks and basement raft slabs as part of a tanking build-up
- Bridge decks and tunnels requiring a durable, movement-tolerant barrier
- Swimming pool shells and water-retaining structures
- Damp-proofing course over foundations and plinth beams
- Base layer in a multi-layer membrane system for critical structures
Key advantages
- High softening point (>=150 C) resists flow and slump on hot, exposed Indian roofs
- Non-woven polyester core delivers high tensile strength (up to 650 N/5 cm) and elongation to bridge cracks and movement
- Instantly waterproof once torched, with no curing wait unlike liquid membranes
- Factory-controlled uniform thickness removes the variability of site-mixed coatings
- Cold flexibility down to -2 C, so it stays crack-free across seasonal swings
- Slate/mineral finish option gives a built-in UV-stable wearing surface for exposed decks
- Carries ASTM D 5147 and IS 16532:2017 for tender and consultant approval
- Non-hazardous and non-flammable in the roll for safe storage and disposal
Limitations & considerations
- Requires skilled torch application; over-heating past the smoking point degrades the compound and voids performance
- Open-flame LPG torching brings fire-safety obligations and is unsuitable near live gas lines, combustibles or in confined unventilated spaces
- Substrate must be cured 28 days, dry (<5% moisture) and properly graded, or blistering and debonding follow
- Lap quality is entirely workmanship-dependent; a missing bitumen bead at the edge is a leak path
- Plain finish needs a protective screed or coating when left exposed to long-term UV
- Not a self-levelling or detailing-friendly system at complex penetrations, where a liquid membrane often finishes better
Selection & best practice
Success is decided at the substrate. Allow new concrete a full 28-day cure, mechanically abrade to remove laitance, and confirm moisture content is below 5 percent before priming. Build the correct fall so water drains, keep drain mouths at least 15 mm below deck level, and form 75 x 75 mm coving at all upstands with polymer-modified mortar. Prime with ShaliTex Primer (or the WB grade) at 0.3 to 0.5 L/m2 and let it go tack-free. Torch both the primed deck and the membrane underside until the surface embossing just disappears, then press the roll forward firmly so a continuous bitumen bead extrudes at every edge; keep end laps at 100 mm and side laps at 75 mm. Never heat past the point where the membrane smokes. Envelope the whole building parapet-to-parapet, seal edges into grooves with a polysulphide or polyurethane sealant, and finish exposed non-trafficable areas with a reflective coat such as SuperSilverShield, or protect foot-trafficable zones with a 50 mm PCC screed or loose-laid tiles. Work only between +5 C and +45 C, and never in rain.
Specifications
| Composition | Five-layer APP (atactic polypropylene) modified bitumen membrane, non-woven polyester reinforced |
| Reinforcement | Spun-bonded non-woven polyester mat, 140 g/m2 |
| Thicknesses available | 2, 3, 4 and 5 mm |
| Softening point | >=150 C (IS 1205 / ASTM D 36) |
| Heat resistance | No flow at 120 C for 2 hours (IS 13826 Part 5) |
| Cold flexibility | Does not crack at -2 C (IS 13826 Part 2) |
| Tensile strength (longitudinal) | 300 to 650 N/5 cm depending on grade (IS 13826 Part 1) |
| Water absorption | 1.0% max (IS 13826 Part 6) |
| Roll size / standards | 2 mm: 1 m x 15 m; 3/4/5 mm: 1 m x 10 m. ASTM D 5147, IS 16532:2017 |
Industry use cases
Commercial and institutional roofs
Large exposed terraces on offices, malls and hospitals where the >=150 C softening point prevents slump under Delhi NCR summer loads and the slate finish serves as the wearing surface.
Residential terraces
Single-layer torch-on waterproofing on independent houses and apartment roofs, enveloped parapet-to-parapet and topped with a protective screed for long-term leak-free service.
Infrastructure
Bridge decks, tunnels and metro structures needing a movement-tolerant, standards-compliant membrane that carries slab thermal cycling without splitting.
Basements and car parks
Below-grade tanking of raft slabs and retaining walls in a multi-layer build-up where the polyester core resists hydrostatic pressure and construction damage.
Landscaped and podium decks
Roof gardens and podiums over habitable space, where a robust torched barrier is protected beneath drainage and planting layers.
Frequently asked questions
What is the difference between APP and SBS membranes, and which suits Indian roofs?
Which thickness should I specify?
Can it be left exposed to the sun?
What surface preparation does it need?
Is torch application safe on an occupied building?
What standards does SuperThermoLay APP comply with?
How we position STP SuperThermoLay APP
SuperThermoLay APP is STP’s answer for hot, exposed roofing; where a project needs greater low-temperature elasticity or high structural movement, the SuperThermoLay SBS grade is the better call, and STP also offers SuperThermoLay AR, FR (fire-retardant) and minus 5 C variants within the same family. Pair the membrane with STP’s own system consumables you will already be specifying: ShaliTex Primer as the bond coat, ShaliSeal PS GG or PU GG sealant at edges and grooves, and SuperSilverShield as the reflective top coat. For below-grade tanking on basements, podiums and tunnels, teams often prefer Fosroc’s Proofex line, which is engineered around aggressive-ground exposure; Space Arc supplies and applies both STP and Fosroc, so the choice can follow the spec rather than the stock.
Related Waterproofing products
Source STP SuperThermoLay APP for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.