Fosroc Proofex Geomembrane
A 25-micron prime-virgin polymer damp proof membrane (DPM) for below-ground structures, sub-slab moisture barriers and tanking back-up — supplied and applied across Delhi NCR and Pan-India.
What is it?
A high-performance thin-film damp proof membrane (DPM) made from prime virgin polymer to a nominal 25 microns (0.25 mm), supplied in rolls and lapped on site with adhesive tape.
Where is it used?
Below-ground and ground-bearing construction — under floor slabs, over blinding concrete, behind retaining walls and as a moisture/separation barrier in basements, foundations and civil works.
Why use it?
It blocks rising damp and ground moisture, resists naturally occurring subsoil acids/alkalis and biological attack (bacteria/fungi), and installs fast with simple taped overlaps, giving a low-cost, durable first line of moisture defence.
How is it applied?
Rolled out over a clean, prepared substrate (typically blinding or compacted sub-base), lapped at joints and sealed on site with adhesive tape; the reflective film is laid before pouring the structural slab.
About Fosroc Proofex Geomembrane
Fosroc Proofex Geomembrane is a thin, high-performance damp proof membrane (DPM) manufactured from prime virgin polymer film to a nominal thickness of 25 microns (0.25 mm). It belongs to Fosroc’s well-established Proofex family of waterproofing membranes and is positioned as an economical, fast-to-install moisture barrier for below-ground and ground-bearing construction. Rather than being a structural tanking sheet on its own, it functions as a continuous physical barrier that stops capillary rise of ground moisture and water vapour into floor slabs and foundations.
The membrane is produced from prime (rather than recycled) base material, which is important for consistency of film quality, puncture behaviour and long-term durability in buried conditions. Fosroc highlights a highly reflective surface, high tensile strength and high elongation/flexibility — properties that let the sheet conform to slightly irregular substrates and tolerate the handling and concrete-placement loads typical of an Indian site. It is designed to remain serviceable throughout the lifetime of the building once cast into the slab build-up.
For contractors, consultants and architects in India, the appeal is practical. Proofex Geomembrane is rolled out over prepared blinding or sub-base, overlaps are sealed on site with adhesive tape, and the slab is poured over it. There is no torching, no priming and no curing time, so it suits tight programmes on basements, podiums, plinths and ground-floor slabs. Because it resists subsoil chemicals and microbial attack, it performs reliably in the variable, often aggressive soils found across NCR, coastal and high-water-table regions. As an authorised Fosroc distributor and applicator, Space Arc Engineering supplies Proofex Geomembrane alongside the wider Proofex waterproofing system so specifiers can match the membrane to the correct primary tanking and detailing products for each project.
The technical insight
Proofex Geomembrane is best understood as a vapour/moisture barrier and slip/separation membrane, not a self-adhesive bonded tanking sheet. At a nominal 25 microns (0.25 mm), it is a thin reflective film whose job is to interrupt capillary moisture and vapour movement rather than to resist significant hydrostatic head on its own. Its performance therefore depends heavily on continuity: every overlap must be lapped generously and taped, penetrations dressed, and the substrate kept free of sharp aggregate that could puncture the film. Where the design has a real water table or hydrostatic pressure, this membrane is used as a back-up/secondary barrier and the primary waterproofing is handled by a heavier Fosroc system such as a self-adhesive sheet (Proofex 3000) or a pre-applied bonded membrane (Proofex Engage). Specifiers should confirm the exact current roll dimensions, tensile and elongation values, and applicable standards from the latest local Fosroc Technical Data Sheet for the supply region, because Fosroc publishes country-specific datasheets (e.g. for India/SEA) and figures can be revised between editions.
Where it is used
- Under-slab damp proof membrane (DPM) for ground-bearing floors, laid over blinding concrete before the structural slab
- Sub-base moisture and vapour barrier in basements, foundations and raft slabs
- Separation / slip membrane between blinding and structural concrete or between concrete and sub-grade
- Secondary (back-up) moisture barrier behind primary below-ground tanking systems
- Protection and isolation layer over compacted fill or hardcore prior to slab casting
- Moisture barrier under screeds and ground-floor build-ups in commercial, residential and industrial buildings
- Temporary protection of horizontal surfaces and reflective vapour-control layer where sunlight exposure is a factor during construction
Key advantages
- Made from prime virgin polymer for consistent film quality and long-term durability when buried
- Effective barrier against rising damp, ground moisture and water vapour into slabs and foundations
- Resistant to naturally occurring subsoil acids and alkalis — suited to aggressive Indian soils
- Biologically inert: unaffected by bacteria, fungi and other soil microorganisms
- High tensile strength with high elongation and flexibility to conform to substrate and resist handling damage
- Fast, low-labour installation — roll out and seal overlaps with adhesive tape; no torch, primer or cure time
- Highly reflective surface, tolerant of sunlight exposure during the construction phase
- Economical first line of moisture defence; integrates with the wider Fosroc Proofex waterproofing system
- Lightweight rolls are easy to transport, store and handle on congested sites
Limitations & considerations
- Thin (nominal 25 microns / 0.25 mm) — a moisture/vapour and damp-proof barrier, not a stand-alone tanking sheet for significant hydrostatic head
- Performance is overlap-dependent: poorly lapped or untaped joints, tears and punctures will compromise continuity
- Requires a clean, smooth, well-prepared substrate; sharp aggregate or debris can perforate the film
- Not a structural or root-resistant membrane and not intended for trafficked or exposed roof waterproofing
- Where a real water table/hydrostatic pressure exists, it must be paired with a primary system (e.g. Proofex 3000 or Proofex Engage)
- Exact roll size, tensile/elongation values and standards vary by region and edition — confirm against the current local Fosroc TDS
- Joints rely on adhesive tape, so installation in wet, dusty or contaminated conditions needs care to achieve a sound seal
Selection & best practice
Lay Proofex Geomembrane over a clean, smooth, debris-free substrate — typically blinding concrete or a well-compacted, levelled sub-base free of sharp projections. Roll out the sheet flat without wrinkles, provide generous side and end overlaps at all joints, and seal every lap continuously with the recommended adhesive tape; dress the membrane neatly around penetrations, columns and upstands. Avoid trafficking the laid film and protect it from tools and reinforcement bar ends before and during concreting. Treat it as part of a system: where there is any hydrostatic pressure or a defined water table, use it as a back-up barrier beneath a primary Fosroc tanking membrane rather than as the sole waterproofing. Always work to the current local Fosroc Technical Data Sheet and method statement for the supply region, and confirm roll dimensions and lap requirements before ordering quantities. Space Arc Engineering can advise on the correct Proofex combination and provide site application support across Delhi NCR and Pan-India.
Specifications
| Product type | Damp proof membrane (DPM) / moisture-vapour barrier sheet |
| Base material | Prime virgin polymer film |
| Nominal thickness | 25 microns (0.25 mm) |
| Surface | Highly reflective; tolerant of sunlight exposure |
| Tensile strength | High (specific value per current local TDS) |
| Elongation / flexibility | High elongation and flexibility |
| Chemical resistance | Resists naturally occurring subsoil acids and alkalis |
| Biological resistance | Unaffected by bacteria and fungi |
| Jointing / sealing | On-site overlap, sealed with adhesive tape |
| Application area | Below-ground / ground-bearing damp proofing and vapour control |
| Supply form | Rolls (confirm width and length against current local Fosroc TDS) |
| Range | Part of the Fosroc Proofex waterproofing membrane family |
Industry use cases
Residential & commercial buildings
Under-slab DPM for ground-floor and basement slabs to stop rising damp and protect finishes, screeds and stored goods from ground moisture.
Basements & deep foundations
Secondary moisture/vapour barrier laid with primary Fosroc tanking on raft slabs and retaining structures where soil moisture and aggressive subsoils are a concern.
Industrial & warehouse floors
Sub-slab vapour barrier under large ground-bearing slabs to keep floors dry for coatings, racking and moisture-sensitive operations.
Infrastructure & civil works
Separation and moisture-control layer between blinding and structural concrete in podiums, plinths, water-retaining and below-ground civil structures.
Roads, podiums & landscaping decks
Reflective barrier and separation layer over compacted fill or hardcore prior to slab casting, protecting the structure from sub-grade moisture migration.
Frequently asked questions
Is Fosroc Proofex Geomembrane a structural waterproofing membrane?
What is it made of and how thick is it?
How are the joints sealed?
Will it survive aggressive Indian soils?
Where exactly should it be installed?
What roll sizes and exact tensile values are available?
How we position Fosroc Proofex Geomembrane
Within the Fosroc range, Proofex Geomembrane sits at the economical, thin-film end of the Proofex waterproofing family — a damp proof and vapour-control layer rather than a heavy tanking membrane. It pairs naturally with primary systems where real water pressure exists: Proofex Engage (pre-applied bonded HDPE membrane that adheres to the poured concrete) for rafts and basements, Proofex 3000 (self-adhesive bituminous sheet) for below-ground tanking, and Proofex GP for general-purpose self-adhesive applications; supporting products such as Nitoseal sealants, Renderoc repair mortars and Conplast admixtures complete the below-ground package. Against competitors, specifiers in India commonly weigh it next to Sika (Sikaplan / SikaProof sheet membranes), MBS/MC-Bauchemie membranes, Dr. Fixit (Pidilite) DPM and pre-applied systems, and STP Limited membranes — many of which offer comparable thin DPM sheets and heavier tanking grades. The honest positioning: choose Proofex Geomembrane when you need a reliable, fast, cost-effective moisture/damp barrier under slabs and as a back-up layer, and step up to a thicker bonded or self-adhesive Fosroc membrane (or an equivalent from Sika/Dr. Fixit/STP) when the design must resist genuine hydrostatic pressure. Space Arc Engineering supplies and applies the full Fosroc Proofex system across Delhi NCR and Pan-India and can specify the correct membrane combination for each project.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.