STP SuperThermoLay Minus 5°C
A torch-applied APP membrane built to stay flexible down to -5°C, so basements, roofs and podium decks don’t crack through North Indian winters.
What is it?
A polyester-reinforced, APP-modified bituminous waterproofing membrane supplied in torch-applied rolls, formulated to hold its flexibility down to -5°C instead of the 0°C most standard APP membranes tolerate.
Where is it used?
Basement tanking, retaining walls, podium decks, protected roofs and terraces, water tanks, sunken slabs, car-park tunnels and bridge decks — mainly on hill-station and northern winter sites where ordinary APP membrane risks cracking.
Why use it?
Standard APP sheeting stiffens as temperature drops, and a stiff membrane cracks at laps and folds when laid or flexed cold. This grade keeps its elongation and lap-joint strength intact at sub-zero site temperatures, so the waterproofing doesn’t fail exactly when it’s needed most.
How is it applied?
Prime with ShaliTex Primer at 0.3 L/m², then torch-weld the roll with an LPG torch (or cold-bond with ShaliBond APP where flame work isn’t permitted), lapping 75mm longitudinally and 100mm transversely, finished with Super Silver Shield on exposed roofs or a 50mm PCC screed dosed with ShaliPlast IW where trafficked.
About STP SuperThermoLay Minus 5°C
SuperThermoLay Minus 5°C belongs to STP Limited’s SuperThermoLay family of torch-applied bituminous membranes. STP is the trading name of Shalimar Tar Products Limited, an 85-year-old Indian manufacturer with a long bitumen-waterproofing history. Construction is familiar: a spun-bonded, non-woven polyester mat runs through the core for tensile strength and lap-joint integrity, set in bitumen modified with Atactic Polypropylene (APP) and proprietary resins. What separates this grade from STP’s regular SuperThermoLay is the resin package, tuned to keep the sheet flexible at -5°C rather than going brittle once the substrate cools.
That distinction matters more than it sounds. Many APP membrane failures in India trace back to how the sheet behaved during a cold-morning application — micro-cracks at folds, laps that never seated, or freeze-thaw flexing a stiff sheet can’t absorb. Space Arc sees this grade specified most on hill-station and high-altitude work — Himachal, Uttarakhand, parts of J&K, and NCR’s colder mornings — usually after a standard membrane already cracked on an earlier project. It isn’t something every site needs, but where winter temperature is a real site variable, it removes an entire failure mode from the waterproofing package.
The technical insight
The chemistry here is about what happens to APP-modified bitumen at low temperature. Atactic Polypropylene lifts a membrane’s softening point and heat stability — this grade holds a softening point of ≥150°C and shows no flow after 2 hours at 120°C, which is why APP membranes are generally trusted over SBS on hot Indian roofs — but that same structure is what makes standard APP sheeting stiffen as temperatures fall, typically losing usable flexibility below 0°C. SuperThermoLay Minus 5°C adjusts the resin and polymer ratio to buy genuine flexibility down to -5°C, without giving up the polyester-reinforced strength (650±150 N/5cm longitudinal lap-joint strength, 45±10% elongation at 23°C) that makes the membrane workable on site. Water absorption is held to 0.2%, in line with what STP publishes across its other SuperThermoLay grades.
Where it is used
- Basement and retaining-wall tanking on winter-schedule sites
- Protected roofs and terraces in single-layer torch-applied systems
- Podium decks and sunken slabs under landscaped or trafficked areas
- Water tanks and reservoirs, including as a base layer under a topping system
- Car-parking decks and underground tunnels needing cold-climate flexibility
- Bridge decks on cold-region infrastructure contracts
- Terrace gardens, as the primary waterproofing layer before growing medium
- Damp-proofing courses as a base layer in multilayer membrane systems
Key advantages
- Cold flexibility down to -5°C — the core reason to choose this over standard APP membrane
- Total impermeability once torch-welded and lapped correctly
- Softening point ≥150°C with no flow after 2 hours at 120°C, so hot-roof performance isn’t traded away for the cold-flex tuning
- Polyester-reinforced tensile and tear strength resists damage during and after installation
- Single-layer application cuts labour, joints and installation error versus multi-coat liquid systems
- Water absorption of just 0.2%, so the membrane itself doesn’t become a moisture path
- Recyclable and free of hazardous or toxic material per the manufacturer’s data sheet
- Can be cold-bonded with ShaliBond APP on sites where open-flame torching is restricted
Limitations & considerations
- Torch application needs trained labour and fire-safety controls — not a DIY or unsupervised-crew product
- Needs a primed, clean, dry substrate; skipping ShaliTex Primer or rushing the dry time undermines adhesion regardless of membrane quality
- Comes only in 3mm and 4mm thickness and standard 1m x 10m rolls, so complex penetrations and upstands still depend on installer skill rather than a pre-formed accessory
- Exposed membrane needs a UV topcoat (Super Silver Shield) or a protective screed on trafficable areas — it isn’t meant to be left bare long-term
- Costs more than STP’s standard SuperThermoLay grade, so it’s worth specifying only where winter conditions genuinely justify it
- The published data sheet doesn’t cite a specific IS/ASTM/BS/EN standard number, so specifiers needing a code reference should confirm current compliance directly with STP
Selection & best practice
Reserve this grade for sites where it earns its keep — hill stations, high-altitude structures, or NCR projects torching on genuinely cold winter mornings — rather than defaulting to it everywhere SuperThermoLay is specified. Prime at the full 0.3 L/m² and respect overnight dry time in humid conditions; lay from the lowest point of a sloped roof upward so laps shed water; hold overlaps at 75mm longitudinal and 100mm transverse and finish every seam with a hot trowel rather than trusting the torch pass alone. Don’t skip the Super Silver Shield topcoat on exposed roofs — UV degrades unprotected bitumen membrane fast in the Indian climate. On trafficable decks, the 50mm PCC screed with ShaliPlast IW is structural to the system’s life, not optional protection. Flood-test or pond the membrane before backfilling or screeding over it — torch-applied membrane failures are almost always installation failures, and far cheaper to fix before the next layer goes on.
Specifications
| Composition | Polyester-reinforced, APP-modified bituminous membrane |
| Cold Flexibility | Up to -5°C |
| Softening Point | ≥150°C |
| Tensile / Lap Joint Strength (Longitudinal / Transverse) | 650±150 / 500±150 N per 5cm |
| Tearing Strength (Longitudinal / Transverse) | 350±100 / 300±100 N |
| Elongation @ 23°C (Longitudinal / Transverse) | 45±10% / 50±10% |
| Water Absorption | 0.2% |
| Heat Resistance | 120°C for 2 hours — no flow |
| Thickness & Pack Size | 3mm & 4mm; rolls of 1m x 10m |
Industry use cases
Hill-station residential and hospitality
Basement and terrace waterproofing for homes and hotels in Himachal, Uttarakhand and similar high-altitude markets, where winter application temperatures routinely fall below what standard APP membrane can handle.
Delhi NCR winter-schedule construction
Basement tanking on projects torch-applied during December–February site conditions, avoiding the lap cracking that shows up on standard membrane laid on cold mornings.
Infrastructure and bridge works
Bridge deck and underground tunnel waterproofing on cold-region contracts specifying a membrane with a defined sub-zero flexibility rating.
Institutional water-retaining structures
Reservoirs and water tanks in northern hill districts, used as a base layer beneath a protective topping system.
Podium and basement developers
Podium decks and sunken slabs on multi-storey developments where waterproofing must be laid and stay serviceable through a full winter before the finish layer goes down.
Frequently asked questions
How is SuperThermoLay Minus 5°C different from STP’s regular SuperThermoLay membrane?
Do we have to torch-apply it, or is there a cold option?
What primer does it need, and how much?
Does the membrane need a topcoat after installation?
Should I choose 3mm or 4mm thickness?
Does Space Arc supply and apply this in Delhi NCR?
How we position STP SuperThermoLay Minus 5°C
SuperThermoLay Minus 5°C is the cold-climate specialist inside STP’s own torch-applied membrane line, which also includes the SBS-modified SuperThermoLay SBS, the heavier-duty SuperThermoLay 7, the fire-retardant SuperThermoLay FR and the aluminium-faced SuperThermoLay AR — worth comparing if your project’s constraint is fire rating or UV exposure rather than cold flexibility. Against the wider market, the closest genuine equivalent is Fosroc’s Proofex Torchseal 4S 250 (-20), an SBS-modified torch-applied membrane rated to a considerably lower -20°C; specifiers on truly extreme high-altitude sites, or who prefer SBS’s elastic-recovery profile over APP, sometimes move to that instead. For most Delhi NCR and northern-plains winter work, though, the -5°C rating on this STP grade already covers the temperature range site crews actually encounter, at a lower cost than reaching for a -20°C-rated alternative.
Fosroc Proofex Torchseal 4S 250 (-20) — Specifiers on genuinely extreme, high-altitude sites — or who simply prefer SBS’s elastic-recovery profile over APP — sometimes choose Fosroc’s Proofex Torchseal 4S 250 (-20), a torch-applied SBS membrane rated to a considerably lower -20°C, instead of this -5°C-rated STP grade.
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