STP SuperThermoLay 7
STP’s 7-layer, torch-applied APP bitumen membrane – the reference grade in the SuperThermoLay range – for roofs, podiums, basements and bridge decks across Delhi NCR and pan-India.
What is it?
A prefabricated, APP-modified bituminous waterproofing membrane, 3 mm or 4 mm thick, built from seven bonded layers around a 75-micron biaxial polymer film core, faced top and bottom with 15-micron HMHDPE film.
Where is it used?
RCC roofs and terraces, podium decks, terrace gardens, bridge decks and basement raft slabs – wherever a single-layer, torch-applied membrane is specified over a liquid coating.
Why use it?
APP-modified bitumen gives it a 150°C softening point and cold flexibility to 2-5°C, so it survives Delhi’s peak summer roof heat and North Indian winters without softening or cracking.
How is it applied?
Primed with ShaliTex Primer, heat-welded on with an LPG torch at 75 mm/100 mm overlaps, then finished with a UV top coat or a protection screed depending on roof traffic.
About STP SuperThermoLay 7
SuperThermoLay 7 belongs to a category Indian contractors trusted long before liquid coatings became the default pitch: the torch-applied, polymer-modified bitumen membrane. STP Limited has manufactured bituminous waterproofing in India for over eight decades, and SuperThermoLay 7 sits at the modern end of that lineage – a seven-layer, APP-modified sheet built around a 75-micron biaxial polymer film and reinforced with a 90-micron HMHDPE film plus a non-woven polyester mat. A liquid membrane’s thickness depends on how evenly a crew troweled it on site; a prefabricated sheet like this arrives factory-set at 3 mm or 4 mm, so that variable is removed before it ever reaches the roof.
On site, it’s heat-welded rather than stuck down or left loose, fusing overlaps into a genuinely continuous sheet instead of taped joints. That fully-bonded, single-layer build is why STP positions it for demanding substrates – bridge decks, podium slabs – where movement and vehicular loading punish weaker systems, alongside routine terrace and basement work. Exposed bitumen degrades under UV over years, so STP pairs it with a reflective top coat (SuperSilverShield) on non-trafficable roofs, or a protective screed with a geotextile layer on decks that carry traffic – the membrane waterproofs; it isn’t meant to be the wearing surface.
The technical insight
The number that matters most on an Indian roof is the 150°C minimum softening point (ASTM D36). Ordinary oxidised-bitumen felts soften well below what a black RCC roof reaches under peak summer sun, and a softened membrane creeps and splits at the laps. APP modification pushes that ceiling comfortably clear of site conditions. At the other end, the pliability test (ASTM D228, 2-5°C, does not break) matters for hill-belt and North Indian winter work, where a stiff membrane cracks the moment it’s unrolled cold. The 90-micron HMHDPE film between the bitumen-polyester layers is what delivers puncture resistance and near-zero water absorption (under 0.15%, ASTM D5147) – a physical barrier independent of the bitumen itself. None of this replaces correct detailing at drains, upstands and construction joints, which is where most real failures start.
Where it is used
- RCC roofs and terraces on residential, commercial and institutional buildings
- Podium decks over basement or multi-level parking in townships and mixed-use projects
- Terrace gardens, laid beneath a root-resistant protection course
- Bridge decks and flyover approach slabs, ahead of the wearing coat
- Basement raft slabs and retaining structures, positive-side application
- Industrial and warehouse roofs, including re-waterproofing jobs
- Water tank exteriors, sunken slabs and sunken toilet/kitchen portions
- Metro/rail platform and tunnel-portal decks where torch-applied systems are specified
Key advantages
- Factory-set 3 mm/4 mm thickness – film build doesn’t depend on hand application
- Fully heat-welded seams form a continuous sheet, not taped joints
- 150°C softening point handles Indian roof heat without slumping
- Cold-flexible to 2-5°C for hill-belt and winter sites
- Internal HMHDPE film adds puncture resistance and near-zero water absorption
- Single-layer install is faster than multi-coat liquid systems
- High tensile and tear strength tolerates normal structural movement
- Established track record on bridge decks and podiums
Limitations & considerations
- Torch work means open flame on site – needs fire clearance and trained applicators; not ideal on occupied buildings
- Seam quality is applicator-dependent; a rushed or under-heated weld is the top cause of site failures
- Exposed bitumen still degrades under UV – a top coat or protective screed is mandatory, adding cost and time
- Not self-healing at punctures the way some liquid membranes claim to be; follow-on trade damage needs a proper patch repair
- Needs a primed, reasonably dry (under 5% moisture) and mechanically sound substrate
- Bulkier and heavier to transport, store and carry to upper floors than liquid drums
Selection & best practice
Get the substrate right before the torch comes out: grind the deck smooth, grout construction joints with ShaliGrout IP, build a minimum 1-in-100 fall, and form 75 mm coving at upstands. Prime with ShaliTex Primer at about 0.3 L per square metre and let it dry fully – overnight in humid weather – since a tacky primer is a common cause of poor adhesion. When welding, aim roughly 75 percent of the flame at the roll and 25 percent at the substrate or previous lap, and always finish overlaps with a hot trowel rather than trusting the torch pass alone; 75 mm longitudinal and 100 mm transverse laps are the minimum, not the target. Decide the protection system – SuperSilverShield or a ShaliPlast IW screed over ShaliGeoText – before starting; retrofitting it after months of foot traffic costs far more.
Specifications
| System / layers | 7-ply APP-modified bitumen membrane; spun-bonded polyester mat + biaxial polymer film core |
| Thickness | 3 mm or 4 mm |
| Roll size | 1 m x 10 m (10 m² per roll) |
| Softening point | 150°C min (ASTM D36) |
| Tensile / lap joint strength | Longitudinal 650 ± 150 N/5cm; Transverse 450 ± 100 N/5cm (DIN 52123) |
| Elongation | Longitudinal 40 ± 10%; Transverse 35 ± 10% (DIN 52123) |
| Tearing strength | Longitudinal 300 ± 100 N; Transverse 250 ± 100 N (ASTM D5147) |
| Cold flexibility (pliability) | 2°C to 5°C – does not break (ASTM D228) |
| Water absorption | < 0.15% (ASTM D5147) |
Industry use cases
Residential high-rise
Terrace waterproofing on a residential tower in Gurugram, torch-applied over a screeded and primed roof slab, finished with SuperSilverShield.
Commercial/podium
Podium deck over basement parking, protected with ShaliGeoText and a loose-laid paver system ahead of landscaping.
Infrastructure
Bridge deck waterproofing beneath the wearing coat on a flyover approach span, chosen for tensile and tear strength under compaction.
Institutional
Basement raft slab of an institutional building, positive-side membrane laid ahead of backfill with 100 mm transverse laps at upstands.
Warehousing/industrial
Warehouse roof re-waterproofing, chosen for a faster single-layer install versus a multi-coat liquid alternative.
Frequently asked questions
Is SuperThermoLay 7 self-adhesive or does it need a torch?
Should I choose the 3 mm or 4 mm thickness?
Does the membrane need a top coat once it’s laid?
Can SuperThermoLay 7 be used below ground, on a basement?
What primer does it need underneath?
How does it compare with STP’s other membranes, like SuperThermoLay FR or SuperTene 7?
How we position STP SuperThermoLay 7
SuperThermoLay 7 is STP’s baseline 7-layer APP membrane and the reference point for the rest of the range: step up to SuperThermoLay FR for fire-retardant performance, to SuperThermoLay Minus 5°C or SBS for harsher cold flexibility, or sideways to SuperTene 7 for a self-adhesive, torch-free lay-down. Pair it with ShaliTex Primer, SuperSilverShield and ShaliGeoText from the same STP system rather than mixing brands across the build-up. Where a project rules out hot works entirely – an occupied building, a fire-sensitive retrofit – Fosroc’s Proofex 3000 is a genuine cold-applied, self-adhesive alternative on a similar HDPE-bitumen composite principle; Space Arc supplies and specifies both.
Fosroc Proofex 3000 — Where a project rules out hot works entirely – an occupied building, a fire-sensitive retrofit, tight urban infill – Fosroc’s Proofex 3000 is a genuine cold-applied, self-adhesive HDPE-bitumen composite membrane that a specifier might choose over a torch-applied APP system like SuperThermoLay 7.
Related Waterproofing products
Source STP SuperThermoLay 7 for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.