Sika SikaProof-315 HDPE SG IN
A pre-applied, fully bonded HDPE sheet membrane that grips freshly cast concrete and shuts down lateral water tracking around basements, rafts and buried structures.
What is it?
A virgin-HDPE self-adhesive sheet membrane, sand-faced and coated with a pressure-sensitive adhesive, that bonds permanently to concrete cast directly against it.
Where is it used?
Below-ground reinforced concrete: basement rafts and walls, subways, tunnels, footings, lift pits and prefabricated structures where the outer face is inaccessible after casting.
Why use it?
Because it is fully bonded, water cannot migrate between the membrane and the slab, so a local puncture stays local instead of tracking across the whole envelope.
How is it applied?
Loose-laid on blinding or fixed to formwork with the adhesive face up, laps sealed 80-100 mm; reinforcement and concrete go straight on top within 45 days, with no protection screed.
About Sika SikaProof-315 HDPE SG IN
SikaProof-315 HDPE SG IN belongs to the pre-applied family of waterproofing systems, the approach specifiers reach for when a structure has to be tanked from the outside but there is no outside to reach once it is built. On a blindside basement wall poured against sheet piling, or a raft cast on lean concrete, you cannot come back later and coat the buried face. The membrane therefore goes down first: the sheet is laid with its adhesive-and-sand face pointing up toward the reinforcement, and the concrete is cast directly onto it. As the fresh mix cures, it keys into that face and the two become one continuous, permanently bonded envelope.
The sheet is built from a virgin, non-recycled HDPE film carrying a high-bond pressure-sensitive adhesive, with a weatherproof sand-sprinkled layer protecting it during construction. That construction gives it real toughness on site: crews can walk it, fix rebar over it and drop chairs on it without a separate screed to protect it. In India the product is declared as a bonded sheet membrane to IS 16471:2017, and its performance is characterised against the ASTM methods that consulting engineers recognise. It is one grade in Sika’s wider preformed-membrane range, positioned above the lighter SikaProof-312 for jobs where a heavier, more robust film is wanted under heavy traffic or aggressive ground.
The technical insight
The value of a pre-applied membrane lives entirely in one word: bond. Loose-laid or post-applied systems sit against concrete but are not married to it, so if water finds a single breach it can travel unseen through the gap between sheet and structure until it surfaces somewhere far from the defect. SikaProof-315 removes that gap. When concrete is placed on the upward-facing adhesive-and-sand layer, cement paste penetrates the sand and the adhesive develops a mechanical and chemical grip on the hardened surface, giving an adhesion in peel of at least 1500 N/m. The result is a full-contact seal with no drainage plane behind it, which is exactly why the datasheet can claim no lateral water migration between the concrete and the membrane. Should the sheet ever be nicked, ingress is confined to that spot rather than pressurising the entire buried face, so remedial injection can be targeted. The HDPE film itself does the heavy structural work, resisting static puncture to 1000 N and staying flexible even at minus 25 degrees C, while its very low water-vapour permeability of under 0.10 ng per Pa per second per square metre and water tightness beyond 71 m of hydrostatic head let it hold back both liquid water and vapour under a high water table.
Where it is used
- Blindside basement walls cast against sheet piling, secant piles or shoring where the external face is permanently inaccessible
- Reinforced concrete base slabs and raft foundations laid over lean-concrete blinding
- Lift pits, plant rooms and other sunken structures sitting below the water table
- Subways, underpasses and cut-and-cover tunnel sections needing continuous below-ground tanking
- Reinforced concrete footings and grade slabs requiring damp-proofing and gas resistance
- Extension and reconstruction works tied into existing buried structures
- Prefabricated and precast concrete elements waterproofed before or during assembly
- Structures in aggressive natural ground water and soils where a durable barrier is essential
Key advantages
- Fully and permanently bonds to the cast concrete, eliminating lateral water tracking behind the sheet
- Pre-applied installation lets crews fix reinforcement and cast directly on top, with no protective screed needed
- Robust virgin-HDPE film resists site traffic and static puncture to at least 1000 N
- High elongation of 500 percent or more gives genuine crack-bridging and accommodates settlement and distortion
- Stays flexible and serviceable down to minus 25 degrees C, useful for cold-store and high-altitude work
- Fully adhered, cold-applied lap joints make installation cleaner and faster than torch-on systems
- Resistant to aggressive ground water and soil, and temporarily UV- and weather-tolerant during the build
- Declared to IS 16471:2017 and characterised to ASTM methods, easing specification and third-party review
Limitations & considerations
- Blindside pre-applied only: it must be installed before reinforcement and concrete, so it is not a remedial fix for an existing leaking structure
- Concrete has to be cast within 45 days of laying the membrane, which ties the waterproofing programme tightly to the concreting sequence
- On double-faced formwork the membrane can debond from the concrete; Sika prefers post-applied systems for those situations
- Prolonged UV exposure degrades performance, so the system must be covered or backfilled promptly after formwork removal
- The bond quality depends on concrete mix design and workmanship, so poor placement can compromise the seal
- Penetrations, construction joints and detailing need additional Sika joint-sealing products and trained applicators to remain watertight
Selection & best practice
Start with a stable, smooth substrate free of standing water; fill gaps and voids of 12-15 mm or more before laying, since the sheet needs uniform support to avoid movement during the pour. Roll out with the sand-and-adhesive face pointing up toward the reinforcement, loose-laid on horizontal or inclined surfaces and fastened on vertical formwork. Seal side laps by overlapping 80-100 mm and peeling the release liner in the longitudinal direction; on transverse laps, scrape off the sanded layer with a hot-air tool first, then overlap 80-100 mm and bond with the SikaProof cold-applied tape, working a pressure roller across every seam to expel air. Detail all penetrations and construction joints with the matching SikaProof ancillary products, then carry out a final walk-over inspection and repair any damage before concreting. Keep ambient and substrate temperature between +5 and +40 degrees C, place concrete within 45 days, and protect the membrane from UV and backfill damage as soon as the formwork comes off. On projects with double-faced formwork, discuss a post-applied alternative with Sika Technical Services before committing.
Specifications
| Chemical base | Virgin HDPE sheet membrane with adhesive layer and sand topping |
| Product declaration | Bonded sheet membrane to IS 16471:2017 |
| Effective thickness | HDPE film > 1.10 mm; membrane composite > 1.50 mm |
| Tensile strength / Elongation | ≥ 25 MPa film / ≥ 500% (ASTM D412 mod) |
| Resistance to static puncture | ≥ 1000 N (ASTM E154) |
| Adhesion in peel / Joint peel | ≥ 1500 N/m (ASTM D903 mod / D1876) |
| Water tightness / Vapour permeability | > 71 m hydrostatic head; < 0.10 ng/Pa·s·m² (ASTM E96 B) |
| Roll size | 20 m long x 1.2 m, 1.5 m or 2.0 m wide |
| Shelf life / Storage | 12 months; dry, +5 °C to +30 °C, out of direct sunlight |
Industry use cases
Commercial and residential basements
Blindside tanking of multi-level basement rafts and retaining walls poured against shoring, where no external access exists post-construction.
Metro and infrastructure
Continuous below-ground waterproofing to cut-and-cover metro boxes, subways and underpasses under a high water table.
Industrial and utilities
Sealing lift pits, pump rooms, tank rooms and buried plant enclosures against ground water and vapour ingress.
Precast and modular
Factory or on-site waterproofing of prefabricated concrete elements before they are integrated into the buried structure.
Repair and extension
Tanking new below-ground extensions and reconstruction works that tie into existing buried concrete.
Frequently asked questions
What is the difference between SikaProof-315 and SikaProof-312?
Can I lay reinforcement straight onto the membrane?
Why must concrete be placed within 45 days?
How are the laps and joints sealed?
Is it suitable for double-faced formwork?
Does Space Arc supply the accessories and provide application support?
How we position Sika SikaProof-315 HDPE SG IN
SikaProof-315 HDPE SG IN is the heavier-duty grade in Sika’s pre-applied preformed-membrane line; where site duty is lighter, the SikaProof-312 HDPE SG IN offers the same fully bonded principle in a lighter film. The system is completed with SikaProof Sandwich Tape-100 IN for lap and detail sealing, and pairs naturally with Sika’s wider waterproofing range for transitions, including SikaSwell swellable joint profiles and Sikadur epoxy detailing at penetrations. For above-ground or remedial faces where a pre-applied sheet is not the right tool, we would steer engineers to liquid-applied options such as Sikalastic. Across our other brands, Fosroc’s Proofex Engage covers the same blindside pre-applied need, while Dr. Fixit and STP membranes serve podium and roof applications rather than deep below-ground tanking.
Fosroc Proofex Engage — A specifier may prefer Proofex Engage when the design calls for a mechanically keyed cell-mesh bond to concrete or where the project already standardises on the Fosroc waterproofing system.
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