About STP SuperThermoLay FR

{“name”:”SuperThermoLay FR”,”slug”:”stp-superthermolay-fr”,”brand”:”STP”,”realProduct”:”yes”,”officialSource”:”https://stpltd.com/wp-content/upload/TDS/SuperThermoLay-FR.pdf”,”category”:”waterproofing”,”metaTitle”:”SuperThermoLay FR | Fire-Retardant APP Membrane | Space Arc”,”metaDescription”:”STP SuperThermoLay FR is a BS 4735 fire-retardant, APP-modified bituminous membrane with a 160 gsm polyester core, torch-applied by Space Arc in Delhi NCR.”,”heroSubtitle”:”A BS 4735 fire-retardant, polyester-reinforced APP torch-on membrane for roofs, basements, tunnels and public-assembly decks that need flame-spread control without giving up the toughness of a standard APP membrane.”,”glance”:{“whatIsIt”:”A pre-fabricated plastomeric waterproofing membrane — APP-modified bitumen reinforced with a 160 gsm spun-bonded non-woven polyester mat, formulated and tested to resist flame spread per BS 4735.”,”whereUsed”:”Protected roofs, basement/podium roof slabs, auditoriums, covered car parks, tunnels and bridge decks — essentially anywhere a fire-rated waterproofing membrane is called for in the fire-NOC or project specification, plus as a base ply under multilayer damp-proofing systems.”,”whyUse”:”It lets a specifier meet a fire-retardancy clause (BS 4735 burning rate under 25 mm/min) without switching to a different, weaker membrane family — the ASTM D-5147 tensile, tear and elongation figures are on par with STP’s standard APP range, so nothing structural is traded away for the FR rating.”,”howApplied”:”Primed with ShaliTex Primer (or cold-bonded with ShaliPrime APP where open flame isn’t allowed), then torch-applied in a single layer with an LPG torch — flame moved in an L-pattern, laps heat-welded and hot-trowelled with 75 mm longitudinal / 100 mm transverse overlaps — and finally protected with a reflective coat or a screed/tile wearing course depending on traffic.”},”technicalInsight”:”The FR performance comes from formulation, not from a coating: the APP-modified bitumen compound itself is tuned to self-extinguish and slow flame travel, verified by the BS 4735 burning-rate test (<25 mm/min). That sits alongside the same 160 gsm polyester reinforcement and ASTM D-5147 tensile/tear/elongation figures used across STP’s SuperThermoLay range, which is why the FR grade doesn’t feel like a compromise membrane on site — softening point stays at 145-150°C+ and heat resistance at 120°C for 2 hours shows no flow, so it holds up under Delhi NCR’s summer roof temperatures as well as the standard grade does. Puncture resistance is rated L-3/I-3 under UEAtc 5.1.9, which in practice means it tolerates foot traffic and light construction debris during the screed-laying stage without needing a separate protection board. One nuance worth flagging to site teams: laying an FR-rated membrane is itself a hot-work activity, since torch-application is the standard fixing method — the fire-retardant property protects the building after cure, not the crew during installation.”,”applications”:[“Podium and covered-car-park roof decks that need fire-NOC-compliant waterproofing over occupied space below”,”Auditoriums, multiplexes and assembly halls where local fire authorities mandate a flame-retardant roofing membrane before occupancy certification”,”Tunnel and underpass linings combining waterproofing with flame-spread control”,”Bridge and flyover deck waterproofing beneath the asphalt wearing course”,”Basement roof slabs at the transition between below-grade tanking and above-grade waterproofing”,”Terraces of hospitals, malls and institutional buildings with high public occupancy and stricter fire codes”,”Base ply in multilayer built-up roofing and damp-proofing systems”,”Industrial roofs adjoining boiler rooms, DG sets or kitchens where flame-spread risk is already elevated”],”advantages”:[“Meets BS 4735 flame-spread/burning-rate requirement without a separate coating or additive step”,”Total impermeability once torch-welded into a homogeneous, seamless sheet”,”Tensile and tear strength (ASTM D-5147) on par with STP’s non-FR APP membranes — no structural trade-off for the fire rating”,”Softening point of 145-150°C+ and no-flow heat resistance at 120°C/2 hr suit Indian roof-surface temperatures”,”Cold flexibility down to -2°C keeps the membrane workable during winter installation and cold nights”,”Inherent acoustic damping from the bitumen-polyester composite, useful on auditorium and terrace slabs”,”Puncture and impact resistance (UEAtc 5.1.9, L-3/I-3) tolerates normal construction traffic before protection is laid”,”Single-layer torch-on installation is faster and has fewer failure points than multi-coat liquid systems”],”limitations”:[“Torch-application is a hot-work activity — installing an FR membrane still needs a fire watch, extinguishers and a trained crew on the roof”,”BS 4735 rates surface flame spread of the finished membrane; it is not a fire-resistance (REI/time-temperature) rating for the whole roof or slab assembly, and cannot substitute for a structural fire engineer’s specification”,”Torching is restricted or disallowed on some occupied-building retrofits and green-rated sites, forcing the cold-bonded ShaliPrime APP route, which is slower and more primer-dependent”,”Left exposed without a UV-protective top coat (Super Silver Shield) or protection screed, any bitumen membrane degrades faster under sun and thermal cycling”,”Seam quality is almost entirely dependent on applicator skill with the torch — under-heated laps are the single most common cause of leaks in APP systems, not membrane failure”,”Not the right product where a true structural fire-resistance rating is required rather than a flame-retardant roofing surface — that calls for a fire-rated deck system, not just an FR membrane”],”bestPractice”:”Keep the substrate moisture below 5%, build a minimum 1:100 fall, and form 75 mm x 75 mm coving at upstands with PCC dosed with ShaliPlast LW+ before the membrane goes down. Correct construction joints first — V-groove, fill with ShaliFix RM C over a ShaliSBR Latex bond coat, and grout at 1 m centres with ShaliGrout IP. Prime with ShaliTex Primer at 0.3 L/m2 (overnight cure in humid weather) or switch to cold-bonded ShaliPrime APP where torching is restricted. Start laying from the lowest point of the slope, heat roughly 75% of the flame onto the roll and 25% onto the substrate and previous lap, and hot-trowel every overlap — 75 mm longitudinal, 100 mm transverse — until excess compound is pressed flush. Finish non-trafficable roofs with Super Silver Shield for UV protection; on trafficable decks, lay a 50 mm PCC screed (with ShaliPlast LW+) or loose tiles over a spot-bonded ShaliGeoText separation layer. Because the whole application is hot-work, get a permit and keep extinguishers and a fire watch on the roof for the duration.”,”specs”:[{“property”:”Chemistry / reinforcement”,”value”:”APP-modified bitumen, 160 gsm spun-bonded non-woven polyester mat core”},{“property”:”Fire performance (BS 4735)”,”value”:”Burning rate < 25 mm/min”},{“property”:”Softening point”,”value”:”≥150°C (3mm & above) / ≥145°C (below 3mm)”},{“property”:”Cold flexibility”,”value”:”-2°C (3mm & above) / 0°C (below 3mm)”},{“property”:”Tensile / lap joint strength, longitudinal (ASTM D-5147)”,”value”:”650 ± 150 N/5cm (3mm & above)”},{“property”:”Elongation @ 23°C, longitudinal / transverse (ASTM D-5147)”,”value”:”40 ± 10% / 50 ± 10% (3mm & above)”},{“property”:”Water absorption”,”value”:”0.2%”},{“property”:”Puncture resistance (UEAtc 5.1.9)”,”value”:”L-3 static / I-3 dynamic indentation”},{“property”:”Pack sizes”,”value”:”2mm: 1m x 15m rolls; 3mm/4mm: 1m x 10m rolls”}],”useCases”:[{“sector”:”Residential/commercial podium”,”detail”:”Fire-NOC-compliant waterproofing over a covered basement car park beneath a landscaped podium deck in a Delhi NCR mixed-use project.”},{“sector”:”Public assembly / entertainment”,”detail”:”Multiplex or auditorium terrace roofing where the local fire department required a BS 4735-tested membrane before granting the occupancy certificate.”},{“sector”:”Infrastructure”,”detail”:”Bridge or flyover deck waterproofing laid beneath the asphalt wearing course ahead of a road-widening project.”},{“sector”:”Underground structures”,”detail”:”Tunnel or utility duct lining needing both waterproofing and controlled flame spread in a confined space.”},{“sector”:”Industrial”,”detail”:”Factory shed roof adjoining a boiler house or DG room, where a flame-retardant roofing membrane reduces risk from adjacent hot-work zones.”}],”faq”:[{“q”:”Is SuperThermoLay FR different from STP’s regular SuperThermoLay membrane?”,”a”:”Yes. The FR grade is formulated and tested to BS 4735 for flame spread; the base SuperThermoLay isn’t certified to that standard. Otherwise both share the same 160 gsm polyester-reinforced APP construction and similar tensile/tear figures.”},{“q”:”Can this membrane be installed without an open flame?”,”a”:”Yes — it can be cold-bonded with ShaliPrime APP where torching isn’t permitted on site, though torch-application with ShaliTex Primer remains STP’s standard, better-bonded method.”},{“q”:”Which thickness should I specify — 2mm, 3mm or 4mm?”,”a”:”2mm is typically used as a base or underlay ply in multilayer systems; 3mm and 4mm are chosen for single-layer exposed roof applications depending on expected traffic and service life. Space Arc can confirm the right grade against your drawings.”},{“q”:”Does the membrane need a protective top coat after laying?”,”a”:”Yes. Non-trafficable roofs should be finished with Super Silver Shield for UV protection; trafficable decks need a PCC screed or loose-laid tiles over a ShaliGeoText separation layer.”},{“q”:”Is this the same membrane used for basement tanking?”,”a”:”It can be, especially at basement roof/podium level where fire code applies. For pure below-grade tanking without a fire-code driver, STP’s standard SuperThermoLay or the anti-root AR grade is often the more cost-effective choice.”},{“q”:”Does Space Arc supply and install SuperThermoLay FR in Delhi NCR?”,”a”:”Yes — Space Arc Engineering is an authorised STP distributor and applicator across Delhi NCR and pan-India, supplying the membrane along with the primers, coving compounds and trained torch-application crews needed to install it correctly.”}],”positioning”:”SuperThermoLay FR sits inside STP’s own APP torch-on family, alongside SuperThermoLay SBS (elastomeric SBS variant for wider temperature swings), SuperThermoLay AR (anti-root, for planted/green roofs), SuperThermoLay Minus 5°C (extra cold flexibility) and the heavy-duty 7-layer grade — Space Arc will help match the right variant when fire-retardancy isn’t the only requirement in play. Outside the STP range, Fosroc’s Proofex Torchseal series (e.g. Torchseal 4PI) is a credible alternative for the same APP torch-on category; a specifier already standardised on Fosroc systems, or on a project where BS 4735 fire certification specifically isn’t the deciding clause, may reasonably choose that route instead.”}

The technical insight

The FR performance comes from formulation, not from a coating: the APP-modified bitumen compound itself is tuned to self-extinguish and slow flame travel, verified by the BS 4735 burning-rate test (<25 mm/min). That sits alongside the same 160 gsm polyester reinforcement and ASTM D-5147 tensile/tear/elongation figures used across STP’s SuperThermoLay range, which is why the FR grade doesn’t feel like a compromise membrane on site — softening point stays at 145-150°C+ and heat resistance at 120°C for 2 hours shows no flow, so it holds up under Delhi NCR’s summer roof temperatures as well as the standard grade does. Puncture resistance is rated L-3/I-3 under UEAtc 5.1.9, which in practice means it tolerates foot traffic and light construction debris during the screed-laying stage without needing a separate protection board. One nuance worth flagging to site teams: laying an FR-rated membrane is itself a hot-work activity, since torch-application is the standard fixing method — the fire-retardant property protects the building after cure, not the crew during installation.

Where it is used

• Podium and covered-car-park roof decks that need fire-NOC-compliant waterproofing over occupied space below
• Auditoriums, multiplexes and assembly halls where local fire authorities mandate a flame-retardant roofing membrane before occupancy certification
• Tunnel and underpass linings combining waterproofing with flame-spread control
• Bridge and flyover deck waterproofing beneath the asphalt wearing course
• Basement roof slabs at the transition between below-grade tanking and above-grade waterproofing
• Terraces of hospitals, malls and institutional buildings with high public occupancy and stricter fire codes
• Base ply in multilayer built-up roofing and damp-proofing systems
• Industrial roofs adjoining boiler rooms, DG sets or kitchens where flame-spread risk is already elevated

Key advantages

• Meets BS 4735 flame-spread/burning-rate requirement without a separate coating or additive step
• Total impermeability once torch-welded into a homogeneous, seamless sheet
• Tensile and tear strength (ASTM D-5147) on par with STP’s non-FR APP membranes — no structural trade-off for the fire rating
• Softening point of 145-150°C+ and no-flow heat resistance at 120°C/2 hr suit Indian roof-surface temperatures
• Cold flexibility down to -2°C keeps the membrane workable during winter installation and cold nights
• Inherent acoustic damping from the bitumen-polyester composite, useful on auditorium and terrace slabs
• Puncture and impact resistance (UEAtc 5.1.9, L-3/I-3) tolerates normal construction traffic before protection is laid
• Single-layer torch-on installation is faster and has fewer failure points than multi-coat liquid systems

Limitations & considerations

• Torch-application is a hot-work activity — installing an FR membrane still needs a fire watch, extinguishers and a trained crew on the roof
• BS 4735 rates surface flame spread of the finished membrane; it is not a fire-resistance (REI/time-temperature) rating for the whole roof or slab assembly, and cannot substitute for a structural fire engineer’s specification
• Torching is restricted or disallowed on some occupied-building retrofits and green-rated sites, forcing the cold-bonded ShaliPrime APP route, which is slower and more primer-dependent
• Left exposed without a UV-protective top coat (Super Silver Shield) or protection screed, any bitumen membrane degrades faster under sun and thermal cycling
• Seam quality is almost entirely dependent on applicator skill with the torch — under-heated laps are the single most common cause of leaks in APP systems, not membrane failure
• Not the right product where a true structural fire-resistance rating is required rather than a flame-retardant roofing surface — that calls for a fire-rated deck system, not just an FR membrane

Selection & best practice

Specifications

Industry use cases

How we position STP SuperThermoLay FR

SuperThermoLay FR sits inside STP’s own APP torch-on family, alongside SuperThermoLay SBS (elastomeric SBS variant for wider temperature swings), SuperThermoLay AR (anti-root, for planted/green roofs), SuperThermoLay Minus 5°C (extra cold flexibility) and the heavy-duty 7-layer grade — Space Arc will help match the right variant when fire-retardancy isn’t the only requirement in play. Outside the STP range, Fosroc’s Proofex Torchseal series (e.g. Torchseal 4PI) is a credible alternative for the same APP torch-on category; a specifier already standardised on Fosroc systems, or on a project where BS 4735 fire certification specifically isn’t the deciding clause, may reasonably choose that route instead.

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