STP TarFelt BH
An IS 1322 hessian-felt classic – hot-bonded with molten bitumen for fully adhered terrace, parapet and sunken-slab waterproofing across Delhi NCR.
What is it?
A hessian-reinforced bitumen felt roofing membrane, IS 1322-1993 Type 3 Grade 1, fully bonded to the deck with hot STP Bitumen 85/25 rather than torch-fused.
Where is it used?
RCC terraces, parapets, balconies, patios, sunken slabs, bridge decks and tunnels, plus retrofit over AC sheet, corrugated iron, timber decking and under Mangalore-tile roofs.
Why use it?
It’s the economical, IS-compliant, fully-bonded waterproofing felt for a conventional terrace job – proven breaking strength, zero leakage at a 300 mm water head, and 85 years of STP’s track record behind it.
How is it applied?
Prime with ShaliTex Primer, mop hot STP Bitumen 85/25 across the deck, unroll and hand-press the felt into the bond coat with 75 mm / 100 mm overlaps, then protect with stone grit, aluminium paint or a PCC/tile screed.
About STP TarFelt BH
TarFelt BH belongs to the older, hot-bonded school of bituminous waterproofing rather than the newer torch-fused or liquid-applied one. A hessian (jute-fibre) core is saturated with straight-run bitumen, coated on both faces with a bituminous compound, and dusted with mica or fine sand so rolls don’t weld together in storage. On site it’s laid into a full mopping of hot STP Bitumen 85/25 rather than self-fused by flame – which is exactly why STP’s own datasheet warns against resealing laps by torching the top surface; the compound simply isn’t formulated for that. It’s manufactured to IS 1322-1993 Type 3 Grade 1, the standard that has governed Indian bitumen felts for decades, by STP Limited, the Delhi-headquartered chemicals major behind the TarFelt range for most of its 85-year history.
For Space Arc’s clients, that translates into a clear brief: specify TarFelt BH when the job is a conventional RCC terrace, parapet or balcony that needs a fully bonded, IS-compliant membrane at a price well below elastomeric torch or liquid systems, and where the extra elongation and UV tolerance of an APP membrane isn’t essential. It’s not the right call for exposed trafficable roofs left without a protective screed, or for detailing-heavy jobs thick with penetrations and movement joints – STP’s own APP and liquid-membrane variants, or a Fosroc system, handle those better. For a straightforward terrace pour, though, it remains one of the most commonly specified line items on an NCR waterproofing BOQ.
The technical insight
Two figures on the datasheet matter most before ordering. Breaking strength – over 135 kg warp, over 90 kg weft, per IS 1322 – tells you the felt survives being pulled taut around corners and drain outlets without tearing. The pressure-head test, no leakage at a 300 mm water column, is a realistic proxy for monsoon ponding on a terrace with slow drains. Water absorption of just 1.2-1.8% shows the bitumen-saturated, mineral-dusted core is keeping moisture out of the hessian itself. What the heat-resistance rating (no flow at 68±2°C for 3 hours) and the “don’t torch to reseal” instruction are really telling installers is that this is a hot-bonded product, not a self-fusing one – the compound bonds permanently once mopped into hot bitumen, but it isn’t the APP/SBS-modified formulation that lets torch-on felts re-melt at the surface. Crews used to torch membranes sometimes miss this and scorch the coating trying to touch up a lap instead of lifting and re-mopping it with fresh hot bitumen.
Where it is used
- RCC terrace waterproofing under a protective screed, tile bed or stone grit finish
- Parapet wall upturns and coving details on flat roofs
- Balconies and open patios exposed to standing water
- Sunken slabs in toilets and wet areas before fill and screed
- Bridge decks and tunnel linings on IS 1322-specified infra projects
- Retrofit waterproofing over corrugated iron and AC sheet roofs
- Wooden decking and false-ceiling tops needing a bitumen barrier
- Traditional sloped roofs under Mangalore tiles on older NCR properties
Key advantages
- Among the most economical fully-bonded waterproofing systems on an Indian BOQ
- Manufactured to IS 1322-1993 Type 3 Grade 1, a recognised national standard
- Fully bonded to the deck via hot bitumen, so a puncture doesn’t let water migrate under the membrane
- Breaking strength (>135 kg warp / >90 kg weft) resists tearing during installation and thermal movement
- Passes a 300 mm water-head test with no leakage, a realistic monsoon scenario
- Flexible enough to dress around parapet upstands and irregular contours
- Wide substrate compatibility – concrete, AC sheet, corrugated iron, timber decking, under-tile roofing
- Backed by STP Limited’s 85-year manufacturing history in Indian waterproofing
Limitations & considerations
- Needs a hot bitumen kettle and trained labour – not a cold or peel-and-stick product, so execution quality depends heavily on the applicator
- Must be protected after laying; left exposed to UV and foot traffic without grit, aluminium paint or a screed, it degrades faster than rated
- Not torch-fusible for repairs – damaged laps need lifting and re-mopping with hot bitumen, not re-torching the top surface
- Hessian reinforcement is less puncture- and tear-resistant than the polyester-reinforced APP/SBS membranes used on premium projects
- Hot bitumen handling adds site safety and logistics overhead (boiler, trained crew, fire precautions) versus liquid or self-adhesive systems
- Shelf life is a modest 12 months, so rolls should be used within a season rather than stockpiled
Selection & best practice
Treat it as a bonded system: clean and repair the substrate, form 75 mm radius cove fillets at wall-to-floor junctions, and prime with ShaliTex Primer at 0.3-0.4 L/m² first. Mop STP Bitumen 85/25 at roughly 1.2 kg/m² per coat, unroll the felt into it while hot, and hand-press to chase out trapped air – overlaps are 75 mm along the length and 100 mm across end joints, non-negotiable. Add one 100 mm drainage outlet per 40 m² so ponding never nears the 300 mm test threshold, and terminate correctly at parapets – straight to the top under 450 mm, or into a sealed groove above that. Never leave the felt as the finished surface: protect it with hot-bonded stone grit, SuperSilverShield aluminium paint on non-trafficable roofs, or a PCC/tile screed (with ShaliPlast IW) wherever there will be foot traffic.
Specifications
| Standard | IS 1322-1993, Type 3 Grade 1 |
| Roll size | 1 m x 20 m (20 m² per roll) |
| Minimum roll weight | 46 kg per roll (± 1%) |
| Breaking strength (warp way) | >135 kg |
| Breaking strength (weft way) | >90 kg |
| Water absorption | 1.2 – 1.8% |
| Bitumen content per roll | 23 – 24.5 kg |
| Heat resistance | No flow at 68 ± 2°C for 3 hours |
| Shelf life | 12 months, stored as recommended |
Industry use cases
Residential terraces
Standard choice for RCC terrace waterproofing on independent houses and builder-floor projects across Delhi NCR, ahead of tile or PCC protection.
Institutional & school buildings
Specified where budgets favour a proven IS-standard felt over premium torch membranes on large flat-roof areas.
Bridges & tunnels
Used on civil infrastructure decks and linings where the waterproofing schedule calls for IS 1322 felt.
Industrial sheds & retrofit roofing
Applied over ageing corrugated iron or AC sheet roofs during retrofit waterproofing programmes.
Heritage & sloped-tile roofs
Laid under Mangalore tiles on older NCR properties needing a bitumen damp-proof layer beneath traditional roofing.
Frequently asked questions
Is TarFelt BH torch-applied like TarFelt APP?
How many rolls do I need for a 100 sqm terrace?
What else does the system need alongside the felt?
Can it be left exposed without tiles or screed?
How long does a TarFelt BH terrace typically last?
How is TarFelt BH different from TarFelt LM?
How we position STP TarFelt BH
TarFelt BH sits at the economical end of STP’s bituminous waterproofing family – step up to TarFelt APP for a polyester-reinforced, torch-applied elastomeric membrane with better elongation and UV tolerance, or to TarFelt LM for a brush-applied liquid membrane on smaller, detail-heavy areas; TarFelt FG and TarFelt BS cover other grade variants under the same IS 1322 umbrella. It’s normally specified alongside ShaliTex Primer and STP Bitumen 85/25 as the bonding coat, and protected with SuperSilverShield aluminium paint or a PCC/tile screed. Where a project genuinely needs a self-fusing, polyester-reinforced torch membrane – aggressive basement or podium tanking, for instance – Fosroc’s Proofex Torchseal 3P/4P is a credible alternative worth comparing on spec and price; Space Arc supplies and applies both STP and Fosroc systems, so the choice comes down to project detailing and budget rather than brand loyalty.
Related Waterproofing products
Source STP TarFelt BH for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.