Fosroc Proofex GP
Cold-applied, self-adhesive polymer-modified bitumen sheet membrane for tanking basements, retaining walls and buried civil structures.
What is it?
A cold-applied, self-adhesive sheet waterproofing membrane built from an internally reinforced polymer-modified bitumen layer bonded to a polyethylene film top surface, with a peel-off silicone release liner on the adhesive face.
Where is it used?
Below-ground tanking of basements, lift pits, retaining walls, podiums, foundations and other building and civil-engineering substructures across Delhi NCR and Pan-India.
Why use it?
It is torch-free and fast to lay, gives a uniform-thickness continuous bond to primed concrete, and removes the fire and flame risk of hot-applied bituminous systems on site.
How is it applied?
Prime the dry, float-finished concrete with Proofex Tackcoat, peel the release paper, press the membrane down with 75mm side and 150mm end laps, then immediately cover with Protection Board or a screed.
About Fosroc Proofex GP
Fosroc Proofex GP is a cold-applied, self-adhesive bituminous sheet membrane engineered for continuously bonded waterproofing of building and civil-engineering substructures. The sheet is a sandwich construction: an internally reinforced, polymer-modified bitumen compound forms the body and the adhesive face, while a tough polyethylene film bonded to the upper surface acts as the protective skin and lap-welding surface. The bitumen adhesive is shielded by a siliconised release paper that is stripped away only at the moment of application, so the membrane self-bonds to the primed substrate without any torch, hot bitumen, bonfire or open flame on site.
For contractors, consultants and architects in India, Proofex GP fills a very specific brief: a dependable, factory-controlled, fixed-thickness tanking sheet for negative-risk areas where liquid-applied coatings are harder to verify and where torch-on felts are undesirable for safety or programme reasons. Because each roll delivers the same nominal membrane thickness end to end, the installed film is not dependent on applicator skill the way a brush- or trowel-applied coating is, which makes site quality assurance and third-party inspection far simpler. The sheet is applied to a Proofex Tackcoat primed surface, lapped, rolled down and then immediately protected from UV and from mechanical damage during back-filling.
The product sits within Fosroc’s wider Proofex range of pre-formed waterproofing membranes and is supported by matching ancillaries — Proofex Tackcoat / Tackcoat WB primers, Proofex Corner Pieces and angle fillets, and Proofex Protection Board — so the whole tanking detail, including junctions and upstands, is covered by one compatible system rather than mixed brands. Note that Fosroc has, in some markets, rationalised the older Proofex GPE name into Proofex GP; specifiers should always confirm the current regional datasheet, as nominal thickness and roll length differ slightly between Fosroc’s regional editions.
The technical insight
Proofex GP is a self-adhesive (cold) modified-bitumen membrane, not a torch-applied APP/SBS felt and not a liquid coating. Its waterproofing function comes from the polymer-modified bitumen mass; the internal reinforcement gives the sheet dimensional stability and tear strength, and the polyethylene facing protects the bitumen and provides a clean lap surface. The performance numbers tell the story of a tanking membrane rather than an exposed roofing sheet: water permeability is Nil under hydrostatic head to DIN 1048, water absorption stays below 0.15% at 24 hours, puncture resistance is a minimum 225 N (ASTM E154), and adhesion both to primed concrete and to itself exceeds 1.8 N/mm (ASTM D1000) — the self-adhesion figure being what makes the 150mm staggered end laps watertight. The adhesive softening point above 105 deg C (ASTM D36) and a low moisture-vapour transmission rate (<0.3 g/m² per 24h, ASTM E96) confirm it is built to sit buried and bonded, not to be left exposed to the sun. The bond is a contact bond formed by the primer, so the single biggest field variable is the substrate: it must be float-finished, dry, frost-free and free of laitance, and the Tackcoat must be allowed to go tack-free before the sheet is laid.
Where it is used
- Tanking of basement raft slabs and retaining walls below the water table
- Lift pits, machine pits and underground tank exteriors
- Foundation and plinth waterproofing protecting concrete from aggressive ground salts
- Podium decks, planter boxes and buried slabs (with protection screed)
- Bridge abutments, box culverts and other buried civil-engineering structures
- Blindside / pre-applied detailing at the wall-floor junction in conjunction with angle fillets and corner pieces
Key advantages
- Cold, torch-free, self-adhesive application — no open flame, hot bitumen or LPG on site
- Factory-controlled uniform membrane thickness, so the installed film does not depend on applicator skill
- Fast to lay, peel-and-stick, which speeds the waterproofing programme on large slabs and walls
- Nil water permeability under hydrostatic head (DIN 1048) and very low water absorption
- Strong self-lap and substrate adhesion (>1.8 N/mm) for reliable, continuous seams
- Robust puncture resistance (min 225 N) suited to back-filling when correctly protected
- Backed by a full Proofex ancillary system — primer, corner pieces, angle fillets and protection board
Limitations & considerations
- Not a final exposed surface — must be covered immediately to protect from UV and mechanical/back-fill damage
- Bond depends entirely on substrate prep: surfaces must be float-finished, dry, frost-free and laitance-free, with primer allowed to go tack-free
- Application temperature window is roughly 5 deg C to 50 deg C; below 15 deg C the back of the sheet may need slight warming for an instant bond
- Solvent-based Proofex Tackcoat is flammable — needs ventilation and ignition control; water-based Tackcoat WB is preferred where possible, though solvent primer is advised on very hot substrates
- Re-priming is required if the primed surface is left more than 24 hours before laying the membrane
- Regional datasheets differ (e.g. 1.6mm / 15m vs 1.5mm / 20m rolls); confirm the current India-market edition before specifying
Selection & best practice
Always start from a sound, float-finished concrete surface that is dry and free of frost, laitance and contamination, and treat junctions first — form a sand/cement mortar fillet at wall/floor slab corners and pre-protect internal and external corners with Proofex Corner Pieces before any sheet goes down. Apply Proofex Tackcoat (or the water-based Tackcoat WB) and let it dry tack-free; re-prime if more than 24 hours pass before laying. Lay the membrane from the lowest level upward on vertical or inclined surfaces, peeling the release paper as you go and pressing the polyethylene face firmly so the bitumen bonds with no trapped air. Maintain a minimum 75mm side lap and 150mm end lap, stagger the end laps, and roll every lap firmly for a positive seal. Then protect the finished membrane immediately, in accordance with BS 8102, using Proofex Protection Board or a sand/cement screed before any back-filling.
Specifications
| Product type | Cold-applied, self-adhesive polymer-modified bitumen sheet membrane, polyethylene-faced |
| Nominal thickness | 1.6mm (Turkey TDS) / 1.5mm (Singapore TDS) — confirm regional edition |
| Roll size | 15m x 1m (Turkey TDS) / 20m x 1m, approx. 23 kg (Singapore TDS) |
| Primer / tack coat | Proofex Tackcoat (solvent) or Proofex Tackcoat WB (water-based), 20 & 200 litre drums |
| Primer coverage | 3–6 m² per litre |
| Side / end lap | 75mm side lap, 150mm end lap (staggered) |
| Tear resistance (ASTM D4073) | 150 N longitudinal / 135 N transverse |
| Adhesion to primed concrete & to self (ASTM D1000) | >1.8 N/mm |
| Puncture resistance (ASTM E154:1993) | Min. 225 N |
| Water absorption (ASTM D570) | <0.15% @ 24 h; <0.9% @ 35 days |
| Water permeability (DIN 1048 pt.5:1991) | Nil |
| Crack bridging (ASTM C836:1995) | 1.5mm |
| Adhesive softening point (ASTM D36) | >105 deg C |
| Moisture vapour transmission rate (ASTM E96) | <0.3 g/m² per 24 h |
| Application temperature range | 5 deg C to 50 deg C |
| Protection standard | Protect immediately per BS 8102:1990 (Protection Board / screed) |
| Shelf life | 12 months in cool, dry conditions, stored horizontally, unopened |
Industry use cases
Residential & commercial basements
Tanking of basement rafts and retaining walls in NCR high-rises and farmhouse cellars where a verifiable, fixed-thickness, torch-free membrane is preferred over liquid coatings for QA and fire safety.
Infrastructure & civil works
Below-ground waterproofing of box culverts, bridge abutments, underpasses and buried tanks, protecting concrete from aggressive ground salts during the structure’s service life.
Water & wastewater structures
External tanking of underground tanks, sumps and pump-house pits subject to hydrostatic head, where Nil water permeability under DIN 1048 is specified.
Lift pits & service pits
Small, congested pits where a self-adhesive sheet lapped against pre-formed corner pieces gives a faster, cleaner result than hot-applied felt in a confined space.
Podiums & landscaped decks
Buried podium slabs and planter boxes where the membrane is laid, lapped and immediately protected with a screed before soil and hardscape are placed.
Frequently asked questions
Is Fosroc Proofex GP a torch-applied membrane?
What thickness and roll size does Proofex GP come in?
Which primer is used with Proofex GP and how much do I need?
What lap widths should be maintained?
Can Proofex GP be left exposed?
How is Proofex GP different from Proofex Engage or Proofex 3000?
How we position Fosroc Proofex GP
Proofex GP is Fosroc’s workhorse self-adhesive bituminous tanking sheet — the cold-applied, fixed-thickness option to reach for when a project wants a verifiable membrane on primed concrete without the fire risk of torch-on felt or the applicator-dependence of liquid coatings. Within the Fosroc range it pairs naturally with Proofex Tackcoat / Tackcoat WB primers, Proofex Corner Pieces, angle fillets and Proofex Protection Board, and sits a step below the more specialised Proofex 3000 (HDPE-carrier, radon/gas-resistant self-adhesive membrane) and Proofex Engage (pre-applied, mechanically-bonding blindside membrane) — specify those where gas protection or cast-against detailing is needed, and GP for conventional post-applied basements and retaining walls. For projects that lean toward liquid-applied tanking instead, Fosroc’s own Brushbond range or polyurethane coatings are the in-house alternatives. Among other brands available in India, credible self-adhesive or sheet-membrane equivalents include Sika’s SikaBit / SikaProof self-adhesive membranes, STP Ltd’s torch-on and self-adhesive APP/SBS membranes, MBS (Mistral) bituminous membranes, and Dr. Fixit’s self-adhesive tapes and membranes for smaller works. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering supplies Proofex GP with the full compatible primer-and-protection system plus trained applicator support, so the tanking detail is delivered as one warranted system rather than mixed brands.
Related Waterproofing products
Source Fosroc Proofex GP for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.