About Fosroc Proofex PGP

Fosroc Proofex PGP is a flexible PVC (polyvinyl chloride) synthetic sheet membrane engineered for the structural waterproofing — or tanking — of tunnels and below-ground structures. Previously sold under the name Proofex Alkorplan, it provides a continuous, factory-manufactured waterproof barrier that can be either loose-laid behind cast concrete or fully bonded to the substrate. The membrane is supplied 2 mm thick in large rolls of approximately 2.1 m width and 25 m length (around 140 kg per roll), which keeps the number of site joints low over large areas such as tunnel inverts and basement rafts. A distinctive feature is the two-tone construction: the upper surface is light grey and the underside is black, so any mechanical damage, puncture or thinning sustained during handling and placement shows up as a colour change and can be repaired before the concrete is poured. Seams between sheets are joined by automatic hot-air welding rather than adhesives or tapes, fusing the PVC into a homogeneous, monolithic barrier. For situations where a bonded system is preferred, Fosroc offers the Proofex PGP GTX (fully bonded) grade, which is glued to the substrate using Proofex PGP GTX adhesive while overlaps are still hot-air welded as in the standard product. The system is completed by a family of detailing accessories — Proofex PGP fitters, flanges and sleeves for fixing and pipe penetrations — and integrates with Fosroc Supercast PVC waterstops and Proofex Sheetdrain drainage/protection layers to build a full waterproofing package.

The technical insight

Proofex PGP belongs to the class of thermoplastic single-ply PVC membranes, and its performance is governed by the same standards used for roofing and tanking PVC sheets. Thickness is verified to EN 1849-2, while tensile and elongation behaviour is assessed to ASTM D412 and EN 12311-2 in both longitudinal and transversal directions, reflecting the orientation-dependent strength of a calendered sheet. Watertightness is demonstrated to BS EN 12390 (Part 8) with no water penetration under pressure, and water-vapour transmission to ASTM E96 is reported as nil — important because below-ground tanking must resist hydrostatic head, not merely shed rain. Resistance to mechanical damage is characterised by puncture resistance to ASTM E154:93 and tear resistance to ASTM D624. The defining feature for buried and landscaped applications is root resistance: the membrane is tested against root penetration (under the UEAtc / CEN protocol, equivalent to the CEN/TS 14416 method cited for the range) and shows no penetration, allowing direct use beneath planters and green roofs without a separate root barrier. The reason a welded sheet membrane outperforms a brush- or spray-applied coating in deep tanking is consistency: every square metre is the rated 2 mm thickness with no pinholes, weak films at edges, or operator-dependent build, and the heat-welded seam is as strong as the parent sheet. This also enables compartmentalisation — welding Supercast PVC waterstops to the membrane to divide the tanking into independent zones, so a single defect leaks only within its compartment and can be located and re-injected rather than flooding the whole structure.

Where it is used

• NATM (New Austrian Tunnelling Method) and sequentially excavated tunnels, installed over a shotcrete substrate and Proofex Sheetdrain drainage layer
• Cut-and-cover tunnels, underpasses, metro stations and cable/utility tunnels
• Deep basements, double/triple-level car parks, lift pits and machine pits subject to hydrostatic water pressure
• Retaining walls and below-ground perimeter walls of commercial and residential structures
• Podium decks, buried/paved roofs and roof gardens over occupied space
• Planter boxes and intensive/extensive green roofs, using the membrane’s inherent root resistance
• Water-retaining and water-excluding civil structures requiring a continuous welded tanking system

Key advantages

• Cold-applied — no flame, torch or hot bitumen kettle on site, reducing fire risk and the need for hot-works permits
• Hot-air welded seams fuse the sheets into a homogeneous, monolithic barrier as strong as the parent membrane
• Two-tone light-grey/black construction makes installation damage instantly visible so it can be repaired before concreting
• Root resistant (no penetration), so it can be used directly under planters and green roofs without a separate root barrier
• Consistent factory-controlled 2 mm thickness with no pinholes or operator-dependent film build, unlike liquid coatings
• Can be compartmentalised with Supercast PVC waterstops to isolate and locate leaks, enabling future re-injection
• Fast to install in large 25 m rolls, covering big areas such as tunnel inverts and basement rafts quickly
• Good puncture and tear resistance plus high flexibility at low temperature for handling in cold conditions
• Available as loose-laid standard grade or Proofex PGP GTX fully bonded grade to suit the structure and substrate

Limitations & considerations

• PVC welding requires trained applicators and automatic/hand hot-air welding equipment, plus seam testing (air-lance/vacuum-box) for quality assurance — not a DIY product
• Substrate must be sound, free of cavities, projecting nibs and running water before installation, so dewatering and surface preparation are prerequisites
• Loose-laid systems generally need a protection/drainage layer (e.g. geotextile or Proofex Sheetdrain) to prevent puncture from the substrate or backfill
• As a thermoplastic, it must be protected from prolonged UV and kept away from sources of heat; long-term performance depends on burial or covering
• PVC membranes can be sensitive to contact with certain bitumen-based products, plasticised materials, solvents and oils — compatibility must be checked
• Detailing at penetrations, internal/external corners and pipe sleeves demands skilled welding using the correct PGP fitters, flanges and sleeves
• Specialised, project-supplied product — not a small over-the-counter purchase; rolls are heavy (~140 kg) and need mechanical handling

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Proofex PGP

Within the Fosroc range, Proofex PGP is the sheet-membrane tanking system for serious below-ground work — tunnels and deep basements — and sits alongside complementary Fosroc products rather than competing with them: Proofex Sheetdrain provides the drainage/protection layer beneath it, Supercast PVC waterstops weld to it for compartmentalisation, and Nitofill/Nitoproof and Proofex Engage (pre-applied bonded) or Proofex 3000 (self-adhesive bituminous) serve adjacent applications. For lighter or simpler jobs, liquid-applied Fosroc systems such as the Brushbond range or Proofex Self-Adhesive PR 15 are often more practical. Against the wider market, Proofex PGP competes with other thermoplastic and bituminous tanking membranes: Sika’s Sikaplan PVC tunnel membranes and SikaProof pre-applied systems, STP’s Cosmofin/loose-laid PVC and HDPE membranes, and bituminous self-adhesive sheets from suppliers such as MBS (Mapei’s range), Dr. Fixit (Pidilite) and IWL/STP. Where the project demands a welded, root-resistant, compartmentalised barrier that can be tested and re-injected — typical of metro tunnels and high-water-table basements — Proofex PGP is a strong, internationally proven choice; for shallow, low-risk or budget-driven work a liquid coating or self-adhesive sheet may be the more economical route. Space Arc Engineering can advise on the right system per project and supply Proofex PGP across Delhi NCR and pan-India.

Related Waterproofing products

View all Waterproofing products →