Fosroc Proofex Self Adhesive PR 20
2 mm cold-applied, SBS-modified bitumen self-adhesive sheet membrane, polyester reinforced with a cross-laminated polyethylene film top, for basements, raft slabs, roofs and cut-and-cover tunnels.
What is it?
A 2 mm thick, cold-applied self-adhesive sheet waterproofing membrane built from an SBS-modified bitumen layer internally reinforced with polyester and faced with a cross-laminated polyethylene film. A silicone release paper protects the adhesive face until the moment of application.
Where is it used?
Basements and raft slabs, medium-to-large domestic, commercial and industrial roof slabs, non-root-resistant roof gardens, external faces of cut-and-cover tunnels, and over GI, aluminium and asbestos corrugated sheets where a stick-on membrane is preferred.
Why use it?
It is torch-free and cold-applied, so there is no flame hazard on site; it bonds continuously to primed substrates, offers high elongation, tensile strength and puncture resistance, and resists hydrostatic head, making it suited to below-grade Indian water-table conditions.
How is it applied?
Float-finish and dry the concrete, apply Proofex Tack Coat primer and let it go tack-free, then peel the release paper and press the membrane firmly onto the substrate with no air pockets, allowing 75 mm side and 150 mm end laps; protect immediately with Protection Board or a sand/cement screed.
About Fosroc Proofex Self Adhesive PR 20
Fosroc Proofex Self Adhesive PR 20 is a pre-formed, cold-applied self-adhesive sheet membrane engineered for structural waterproofing and damp-proofing where a torch-applied membrane is undesirable or unsafe. Each 2 mm sheet is a composite: a core of SBS (styrene-butadiene-styrene) modified bitumen, internally reinforced with a polyester carrier for dimensional stability and tear strength, bonded to an outer cross-laminated polyethylene film that resists puncture and abrasion. The underside is a pressure-sensitive polymer-bitumen adhesive protected by a siliconised release paper that is stripped just before bonding to a Proofex Tack Coat primed surface.
For Indian contractors and consultants, the appeal of PR 20 is two-fold. First, it removes the open flame from the waterproofing sequence, which matters on congested basement rafts, occupied buildings, fuel-sensitive sites and tunnels where hot works are restricted. Second, the self-adhesive system gives a fast, repeatable, full-bond application that is far less dependent on torching skill than a built-up bituminous membrane. The membrane handles thermal movement, does not age prematurely when laid correctly, and is positioned as a durable below-grade and roof solution. Space Arc Engineering, as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, supplies PR 20 alongside the companion Proofex Tack Coat primer, Proofex Corner Pieces and Protection Board needed to complete a warranted system.
The technical insight
The defining feature of PR 20 is its SBS-modified bitumen core rather than an oxidised or APP bitumen. SBS is an elastomeric modifier, so the compound behaves like rubberised bitumen: it stays flexible at low temperature and recovers elastically after stretching, which is why Fosroc quotes a polymer-modified bitumen elongation in excess of 2000% (ASTM D 146-04) for the compound itself, and a membrane elongation of around 40% longitudinal and transverse (ASTM D 638) once the polyester reinforcement is engaged. The polyester carrier is the load-bearing skeleton that delivers the 800 N/5 cm longitudinal and 660 N/5 cm transverse tensile strength and 440 N/5 cm tear resistance, while the cross-laminated PE film resists puncture (680 N, ASTM D 4833/5494). A 115 deg C softening point (ASTM D-36) and 0 to -5 deg C cold flexibility with no cracking (ASTM D 836) bracket its service envelope. Crucially, performance is conditional on the bond: the membrane is only as good as the Proofex Tack Coat priming, the float-finished dry substrate and the firmly rolled laps. Trapped air, dust, laitance or moisture under the sheet will defeat the lap adhesion (2.2 N/mm, ASTM D 1000) and create blistering or de-bonding paths for water.
Where it is used
- Below-grade tanking of basement walls and raft/foundation slabs in high-water-table zones
- Medium-to-large roof slabs on domestic, commercial and industrial buildings
- Non-root-resistant roof gardens and landscaped terraces (where root resistance is not a requirement)
- External waterproofing to cut-and-cover tunnels and underground structures
- Stick-on waterproofing over GI, aluminium and asbestos corrugated sheet roofing
- Damp-proofing of masonry and concrete substrates in horizontal and vertical planes
- Wet areas and podiums where torch application is restricted by fire or occupancy constraints
Key advantages
- Cold-applied and self-adhesive: no torch, no LPG, no flame hazard on site
- Fast, repeatable application that is less dependent on operator torching skill
- High elongation and flexibility to accommodate thermal and structural movement
- High tensile strength (800/660 N/5 cm), tear (440 N/5 cm) and puncture resistance (680 N)
- SBS-modified bitumen stays flexible in cold weather (no cracking at 0 to -5 deg C)
- Resists hydrostatic head (60 m water head) for confident below-grade use
- Cross-laminated PE film top resists mechanical damage during backfill
- Environment-friendly with no early ageing when laid correctly per specification
Limitations & considerations
- Requires Proofex Tack Coat priming and a float-finished, dry, laitance-free substrate; bond quality governs performance
- Application temperature limited to 5 deg C to 50 deg C; below 15 deg C the membrane back may need slight warming and material should be stored above 20 deg C before use
- Membrane is flammable and Proofex Tack Coat contains volatile flammable solvents, requiring ignition-source control during priming
- Not root-resistant, so it is unsuitable for green roofs where root penetration must be stopped without an added root barrier
- Always needs immediate mechanical protection (Protection Board or sand/cement screed) ahead of backfill or traffic, per BS 8102:2009
- 12-month shelf life; rolls must be stored horizontally, cool and dry, not more than one pallet high
- Air pockets, dust or moisture trapped under the sheet cause blistering and de-bonding; careful rolling of all laps is essential
Selection & best practice
Begin with a float-finished concrete surface that is dry, frost-free and free of laitance, cavities and projecting nibs. Form a smooth fillet at wall/floor junctions with sand/cement mortar and pre-protect internal and external corners with Proofex Corner Pieces. Apply Proofex Tack Coat at roughly 3-6 m2 per litre and allow it to dry tack-free; re-prime any area left longer than 24 hours. Peel the silicone release paper and bond the sheet firmly, working out air pockets, laying from the lowest level upwards on vertical and inclined surfaces. Maintain a minimum 75 mm side lap and 150 mm end lap, stagger end laps, and roll every lap firmly to seal it. Protect the finished membrane immediately with Protection Board or a sand/cement screed in line with BS 8102:2009 before any backfilling or follow-on trades.
Specifications
| Product type | Cold-applied self-adhesive SBS-modified bitumen sheet membrane |
| Reinforcement / facing | Internally polyester reinforced; cross-laminated polyethylene film top face |
| Membrane thickness | 2 mm (+/- 5%) (UEAtc M.O.A.T. 30) |
| Nominal weight | 2.28 kg/m2 (UEAtc M.O.A.T. 30) |
| Tensile strength (longitudinal / transverse) | 800 / 660 N/5 cm (ASTM D 638) |
| Elongation of membrane (long. / trans.) | 40% / 40% (ASTM D 638); compound elongation >2000% (ASTM D 146-04) |
| Tear resistance (long. / trans.) | 440 / 440 N/5 cm (ASTM D 5147) |
| Softening point | 115 deg C (ASTM D-36) |
| Cold flexibility (0 to -5 deg C) | No cracks observed (ASTM D 836) |
| Resistance to hydrostatic head | 60 m water head (ASTM D 5385); no leakage (DIN 52123) |
| Lap adhesion strength | 2.2 N/mm (ASTM D 1000) |
| Puncture resistance | 680 N (ASTM D 4833 / 5494) |
| Primer | Proofex Tack Coat (coverage 3-6 m2 per litre; 20 & 200 litre drums) |
| Roll size | 15 m long x 1 m wide |
| Application temperature | 5 deg C to 50 deg C |
| Flash point | Membrane > 65 deg C; Proofex Tack Coat > 38 deg C |
| Shelf life / storage | 12 months, stored horizontally, cool and dry, max one pallet high |
Industry use cases
Commercial & residential basements
Tanking of basement walls and raft slabs in Delhi NCR’s variable water table, where the torch-free, fully bonded system speeds congested-site sequencing and avoids hot-work permits.
Metro & infrastructure tunnels
External waterproofing to cut-and-cover tunnel boxes and underground utilities, where flame-free application and 60 m hydrostatic resistance suit deep, wet ground conditions.
Industrial & warehouse roofing
Stick-on membrane over large roof slabs and GI/aluminium/asbestos corrugated sheets, giving fast coverage without torching near sensitive stored goods or processes.
Podiums & landscaped decks
Damp-proofing of podium slabs and non-root-resistant roof gardens, used with a separate root barrier where planting is involved and always with overlying protection.
Renovation & occupied buildings
Waterproofing works in occupied or fire-restricted premises where open-flame torch membranes are not permitted, leveraging the cold-applied self-adhesive format.
Frequently asked questions
What exactly is Proofex Self Adhesive PR 20 made of?
Does PR 20 need a primer, and which one?
What lap dimensions and roll size should we plan for?
What temperatures can PR 20 be applied and stored at?
Is PR 20 suitable for green roofs and roof gardens?
Does it need a protection layer after installation?
How we position Fosroc Proofex Self Adhesive PR 20
Within the Fosroc Proofex range, PR 20 sits as the 2 mm self-adhesive sheet option for cold, torch-free waterproofing. It is closely related to Proofex Self Adhesive PR 15 (the thinner sibling in the same family) and Proofex Self Adhesive Geotext, and it relies on the Proofex Tack Coat primer, Proofex Corner Pieces and Protection Board accessories. For projects that require a more robust pre-applied or bonded HDPE system against blind-side or aggressive ground conditions, Fosroc’s Proofex Engage and Proofex 3000/3000MR torch-applied membranes are the natural step-up alternatives. Against the wider Indian market, PR 20 competes with self-adhesive and SBS membranes such as Sika’s Bituminous self-adhesive ranges (Sika BituSeal / SikaBit), the Pidilite Dr. Fixit Torchshield and Newcoat lines, STP’s Insuboard/membrane offerings, and MBS membrane products. Specifiers comparing these should weigh PR 20’s documented SBS-modified, polyester-reinforced build, 60 m hydrostatic resistance and torch-free format against the polymer, thickness and reinforcement of the alternative, and verify each TDS for the standard claimed. Space Arc Engineering can supply PR 20 as a complete warranted system with priming, detailing and protection materials, and can advise where a liquid-applied or pre-applied Fosroc alternative would serve the structure better.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.