About Fosroc Proofex OFB Adhesive

Fosroc Proofex OFB Adhesive is the dedicated bonding agent for the Fosroc Proofex OFB waterproofing system, a fleece-backed synthetic TPO/FPA (thermoplastic polyolefin / flexible polypropylene alloy) sheet membrane used for fully adhered above-ground waterproofing. On its own the adhesive is not a waterproofing layer; it is the chemistry that locks the membrane permanently to the deck so the assembly behaves as one monolithic, fully bonded system rather than a loose-laid sheet. That distinction matters in Indian construction, where loose-laid or partially bonded membranes are a common cause of lateral water migration beneath the sheet when a single puncture or lap failure occurs. By keying into the polyester fleece on the underside of the Proofex OFB sheet, the adhesive removes the void path, so even local damage stays local and is far easier to trace and repair. Chemically it is a solvent-free, moisture-curing polyurethane. It contains no solvents and no plasticisers, which means very low odour and no VOC release on site, an increasingly important factor for occupied buildings, hospitals, and green-rated projects pursuing IGBC or GRIHA credits. Curing is triggered by ambient humidity, so the product is well matched to most Indian climatic zones, though it makes cold, very dry winter mornings in the north slower to cure and humid monsoon conditions faster. The system it serves, Proofex OFB, is a grey-topped, black-backed TPO/FPA membrane available in 1.2 mm and 1.5 mm thicknesses, supplied in 2.1 m wide by 25 m rolls (about 50 m2 per roll), with hot-air-welded 50 mm minimum laps and proven root resistance for green roofs. The adhesive is supplied separately in a 12 kg pail (Fosroc code FC007105-12KG) and is the component that converts that sheet into a fully bonded, trafficable, planted, or ballasted roof or podium deck. For contractors and consultants in Delhi NCR and across India, Space Arc Engineering supplies this as part of the complete Proofex OFB package alongside Proofex OGP detailing strip, internal/external corner pieces, and Proofex Metal Strip for upstand terminations.

The technical insight

The performance-defining number is the concrete bond strength of greater than 0.63 N/mm2 measured to EN 13596, which exceeds the cohesive tensile strength of most sound concrete substrates, meaning a correctly prepared joint typically fails in the concrete, not the glue line. This is why surface preparation governs the result: the deck must be sound, dry of running water, free of laitance, curing compounds, paint, and projecting nibs, because the PU cannot develop full strength over a weak or contaminated skin. The product is single-component and moisture-curing, with a specific gravity of 1.09 and a high flash point (>200 degrees C), so it is not classed as a flammable solvent adhesive on site. The application window is the critical site discipline: spread at about 0.2 kg/m2, leave 5-10 minutes for tack, then bed the membrane before a skin forms. Because cure is humidity-driven, full cure runs roughly 1 to 5 hours depending on temperature and humidity, so crews in dry winter NCR conditions should expect the slower end and avoid over-spreading ahead of the membrane gang. Lightly moistening the fleece face before rolling it in accelerates the initial grab, and a second press at 30 minutes consolidates the bond. The selvedge laps are not adhered to the deck; they are hot-air welded to a minimum 50 mm weld so the waterproofing continuity is entirely a welded-seam function, while the adhesive’s job is the field bond.

Where it is used

• Fully bonded podium-deck waterproofing beneath paving, planters, and landscaping
• Flat and sloping concrete roof waterproofing where a fully adhered TPO system is specified
• Green roofs and garden roofs, paired with the root-resistant Proofex OFB membrane
• Terrace and intermediate roof decks on residential and commercial towers
• Plaza decks and over-basement slabs in mixed-use developments
• Refurbishment overlays where a mechanically and chemically anchored membrane is preferred over loose-laid sheets

Key advantages

• Solvent-free and zero-VOC, with no plasticisers, suitable for occupied buildings and green-rated projects
• High bond strength to concrete of >0.63 N/mm2 (EN 13596), generally exceeding substrate cohesive strength
• Creates a fully bonded system that prevents lateral water tracking under the membrane
• Single-component, moisture-curing, ready to use with no mixing or catalyst
• Fast tack (5-10 minutes) and full cure in approximately 1-5 hours for quick progress
• High flash point (>200 degrees C), so it is not a flammable solvent adhesive on site
• Bonds the membrane fleece to most common cementitious building materials

Limitations & considerations

• Bonds Proofex OFB to the deck only; it is not itself a waterproofing membrane and does not replace welded seams
• Requires a sound, dry, contamination-free substrate; cannot develop strength over laitance, curing compounds, or running water
• Cure speed is humidity- and temperature-dependent, slowing in cold dry winter conditions and accelerating in monsoon humidity
• Limited working window once spread, so it must not be over-applied ahead of the membrane crew before skin formation
• Metal substrates require prior adhesion testing as performance is not guaranteed without it
• 9-month shelf life and sensitivity to heat during storage demand careful stock rotation
• Application is specialised and best executed by trained or Fosroc-approved applicators rather than general labour

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Proofex OFB Adhesive

Proofex OFB Adhesive should be understood strictly as one component of the Fosroc Proofex OFB fully bonded TPO system, not a stand-alone product; it works hand in hand with the Proofex OFB membrane, Proofex OGP detailing strip and corner pieces, and Proofex Metal Strip for terminations. Within the wider Fosroc range it sits alongside alternative waterproofing routes such as the Proofex 3000 / Proofex Engage pre-applied HDPE membranes used below grade, and liquid-applied systems like Brushbond and Nitcoproof, which suit different exposures; OFB is specifically the above-ground, fully adhered sheet solution for podiums, roofs, and green roofs. Compared with competing fully adhered or self-adhered membrane systems in India, credible alternatives include Sika’s Sarnafil and SikaProof TPO/PVC membrane systems, MBS (myk-arment) and STP Limited membrane and adhesive lines, and the Dr. Fixit roofing membrane range; each pairs its own sheet with its own proprietary adhesive, and these adhesives are generally not cross-compatible. The honest position is that the OFB adhesive’s value is realised only when used with the matched Proofex OFB membrane and installed by trained applicators on a properly prepared deck. For purely liquid-applied or below-grade waterproofing, a different Fosroc product, or a Sika, STP, or Dr. Fixit equivalent, may be the better technical fit, and Space Arc Engineering can advise on the right system per application.

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