Fosroc Membrane HDPE-P
Pre-applied HDPE pressure-sensitive adhesive membrane that bonds fully to poured concrete for blindside basement and below-grade tanking, even where there is no working space.
What is it?
A pre-applied, three-layer HDPE waterproofing membrane combining a high-density polyethylene carrier film, a pressure-sensitive adhesive layer and a trafficable protective coating that forms a continuous mechanical and adhesive bond to freshly poured concrete.
Where is it used?
Blindside and confined-space basements, raft slabs, retaining walls against shored/piled/gunited faces, lift pits, water tanks, tunnels and other below-ground civil structures requiring Grade 1-3 tanking under BS 8102 / IS 16471.
Why use it?
It bonds integrally to the concrete so water cannot track laterally between membrane and structure, eliminating the migration problem of loose-laid sheets, and it installs with no primer, no torching and no protection screed in zero-working-space conditions.
How is it applied?
Rolled out adhesive-side up on blinding (horizontal) or fixed mechanically to vertical shoring, laps overlapped 75 mm and sealed with HDPE sealed tape, then reinforcement is fixed and structural concrete is cast directly against it to develop the integral bond.
About Fosroc Membrane HDPE-P
Fosroc Membrane HDPE-P is a pre-applied tanking membrane engineered for the most demanding part of below-ground waterproofing in India: the blindside condition, where a retaining wall is cast hard against a sheet pile, secant pile, soldier-pile-and-lagging or shotcreted soil face and there is simply no room to apply waterproofing from outside after the wall is built. In congested Delhi NCR, Mumbai and Bengaluru basements, this is the rule rather than the exception, and conventional externally-applied membranes or coatings cannot be installed at all. With Fosroc Membrane HDPE-P, the membrane goes down first, the reinforcement is fixed, and the structural concrete is poured directly onto it. The pressure-sensitive adhesive and the textured surface mechanically key into the wet concrete, so the cured slab and the membrane behave as one. The defining advantage of this integral bond is that if water ever finds a defect, it cannot travel sideways in the gap between membrane and concrete the way it does under a loose-laid sheet, so a single puncture stays a local problem instead of flooding the whole basement through an untraceable path. The membrane carries Fosroc’s verified physical property set: 1.2 mm, 1.5 mm or 1.8 mm total thickness, tensile strength greater than 27 MPa to ASTM D412, elongation over 500%, puncture resistance above 1000 N to ASTM E154, peel adhesion to concrete exceeding 1500 N/m, and resistance to a hydrostatic head greater than 70 m to ASTM D751. It is an inert HDPE product, so unlike some bituminous systems it will not react with ponded waste water, alkalis or hydrocarbons sitting on it before the pour. For Space Arc Engineering’s specifiers and contractors, it is the system of choice for deep rafts and perimeter walls where the older approach of brick-protected bituminous membranes is both slow and unreliable. It is supplied as part of a complete Fosroc tanking package alongside HDPE sealed tape, sanded tape for corners and upstands, and Fosroc hydrophilic and PVC waterstops at construction and movement joints, so the whole below-ground envelope is detailed from a single compatible source rather than mixing brands across critical interfaces.
The technical insight
The performance of Fosroc Membrane HDPE-P comes from its three-layer construction working in sequence. The HDPE carrier film provides the puncture, tensile and chemical barrier; the pressure-sensitive adhesive develops the bond to concrete; and the trafficable top layer protects the adhesive on site and lets steel-fixers walk and place reinforcement without damaging it, which removes the need for a separate screed. The integral concrete bond is the key concept: the membrane is laid adhesive-side toward the pour, and as the fresh concrete cures it grips both the adhesive and the textured surface to form a watertight mechanical and adhesive seal at the membrane-concrete interface. This is what defeats lateral water tracking. Because HDPE is chemically inert, the membrane is unaffected by the aggressive ground salts, sulphates and chlorides common in Indian made-up ground, and it tolerates ponded waste before the pour without reacting. Practically, two numbers govern the install: laps are overlapped 75 mm and sealed (HDPE sealed tape over cut joints, applied to 100 mm width by hot-air welding), and where the membrane is on removable shuttering, a minimum concrete compressive strength of 10 N/mm2 should be reached before stripping so the bond is not disturbed. The membrane also resists a hydrostatic head over 70 m, far beyond any practical Indian basement water table, and stays flexible below -25 C with no cracking.
Where it is used
- Blindside basement perimeter walls cast against sheet-pile, secant-pile, soldier-pile or shotcrete soil-retention faces with zero working space
- Below-ground raft slabs and foundation mats where horizontal pre-applied tanking is laid on the blinding before reinforcement
- Deep basements (2-5 levels) under commercial towers, malls, hospitals and metro stations in high-water-table zones
- Lift pits, sump pits and other localised deep excavations requiring continuous Grade 3 dry tanking
- Retaining walls and box structures in civil and infrastructure works including underpasses and cut-and-cover tunnels
- Water-excluding structures and tanks needing protection against aggressive ground salts, sulphates, chlorides and hydrocarbons
Key advantages
- Bonds integrally to poured concrete via pressure-sensitive adhesive, preventing lateral water migration between membrane and structure so a defect cannot flood the whole basement
- Pre-applied design works in zero-working-space blindside conditions where external membranes cannot be installed at all
- No primer, no torching/flame and no separate protection screed required, speeding the programme and improving site safety
- High verified performance: >27 MPa tensile (ASTM D412), >500% elongation, >1000 N puncture (ASTM E154), >1500 N/m peel to concrete
- Inert HDPE film resists aggressive ground salts, chemicals and hydrocarbons and will not react with ponded waste before the pour
- Trafficable protective top layer lets steel-fixers work directly on the membrane without damaging the adhesive
- Withstands hydrostatic head >70 m and stays flexible below -25 C, with a self-adhesive selvedge and full Fosroc waterstop range for a single-source detailed system
Limitations & considerations
- Performance depends entirely on the integral concrete bond; if the membrane is laid the wrong way up or the bond is broken, lateral water tracking can occur and the system fails
- Requires a float-finished, dry blinding or shoring face free of cavities, projecting ribs, laitance, frost and contamination as a substrate
- Lap sealing demands care – 75 mm overlaps, 100 mm sealed-tape coverage and firm rolling/hot-air welding; poor lap workmanship is the most common cause of leaks
- Backfill must be free of sharp objects and must not contain bricks, blocks or boulders larger than 50 mm or the membrane can be punctured
- Penetrations such as pipe entries need bespoke detailing and should be referred to Fosroc rather than improvised on site
- Pre-applied systems are unforgiving of remedial repair once concrete is cast, since the membrane is then permanently bonded and buried
Selection & best practice
Lay Fosroc Membrane HDPE-P adhesive-side toward the pour on a float-finished, dry, contaminant-free blinding or shoring face. Overlap each roll 75 mm, stagger end joints by half a roll length, and seal all cut joints with Fosroc HDPE sealed tape to 100 mm width by hot-air welding, finishing corners and upstands with sanded tape; roll every lap firmly to guarantee adhesion. Detail all construction and movement joints with Fosroc hydrophilic or PVC waterstops and refer pipe penetrations to Fosroc for approved details. Cast structural concrete directly against the membrane and, on removable shuttering, reach a minimum 10 N/mm2 compressive strength before stripping. Protect the laid membrane from sharp debris, ensure backfill contains nothing larger than 50 mm, and store unopened rolls flat in cool, dry, shaded conditions within the 36-month shelf life.
Specifications
| Total thickness | 1.2 mm, 1.5 mm & 1.8 mm |
| Bare film thickness | 1.2 mm (available for 1.5 mm thick membrane) |
| Tensile strength | >27 MPa (ASTM D412) |
| Elongation | >500% |
| Puncture resistance | >1000 N +5% (ASTM E154) |
| Peel adhesion to concrete | >1500 N/m (ASTM D903 Modified) |
| Resistance to hydrostatic head | >70 m (ASTM D751-06) |
| Lap joint strength | 1500 N/m (ASTM D1876) |
| Low temperature flexibility | < -25 C, no crack |
| Linear dimensional change | 0.1% (ASTM D1204) |
| UV exposure (45 days) | No change (ASTM G153) |
| Standards compliance | BS 8102:2022 & IS 16471:2017 (Grades 1, 2 & 3) |
| Roll size | 1.5 x 20 m |
| Shelf life | 36 months in unopened packaging, cool/dry, flat |
Industry use cases
Commercial high-rise basements (Delhi NCR / Gurugram)
Multi-level car-park and retail basements built blindside against secant or contiguous pile walls in high-water-table corridors use HDPE-P as the pre-applied perimeter and raft tanking to achieve Grade 3 habitable dry space.
Metro and infrastructure
Cut-and-cover tunnel boxes, station boxes and underpasses cast against shored faces rely on the integral-bond pre-applied membrane to prevent lateral water tracking across long structures where loose-laid sheets would be untraceable to repair.
Hospitals and institutional buildings
Deep service basements and lift/sump pits requiring guaranteed dry, mould-free environments for equipment and records use HDPE-P with hydrophilic waterstops at all construction joints.
Water-retaining and industrial structures
Tanks, treatment structures and plants in chemically aggressive made-up ground exploit the inert HDPE film’s resistance to ground salts, sulphates and hydrocarbons for long-term durability.
Frequently asked questions
What is Fosroc Membrane HDPE-P used for?
How is HDPE-P different from a loose-laid or self-adhesive membrane?
Can it be installed where there is no external working space?
What are the verified key specifications?
How are the laps and joints sealed?
Does Space Arc Engineering supply HDPE-P across India?
How we position Fosroc Membrane HDPE-P
Fosroc Membrane HDPE-P sits in Fosroc’s pre-applied tanking family alongside Fosroc Membrane HDPE-S (the self-adhesive variant for vertical faces with working space) and is typically specified with Fosroc hydrophilic and PVC waterstops at joints; for positive-side liquid systems Fosroc also offers Brushbond and Proofex ranges. Its closest competitors in the Indian blindside-membrane market are Sika’s pre-applied SikaProof and Sikaplan systems, Dr. Fixit (Pidilite) pre-applied HDPE membranes, STP Limited’s pre-applied/HDPE tanking sheets, and MBS/CICO offerings. Honestly positioned, HDPE-P competes on its verified high tensile (>27 MPa) and puncture (>1000 N) figures, its inert chemical resistance, and Fosroc’s single-source compatible accessory and waterstop ecosystem; the trade-off is that, like all pre-applied integral-bond membranes, it is workmanship-sensitive at laps and effectively unrepairable once buried, so Sika or comparable systems may be preferred where a contractor’s track record or commercial terms favour them. For Space Arc clients it is the strongest choice when the integral concrete bond and a fully Fosroc-detailed below-ground envelope are the priority.
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