Fosroc Supercast WB
Centrally-placed PVC water bar that seals construction and movement joints in cast in-situ concrete — the embedded first line of defence for tanks, basements and tunnels.
What is it?
A flexible, high-grade PVC waterstop (water bar) extruded as a continuous profile that is cast centrally into a concrete joint to form an integral water seal.
Where is it used?
Construction and movement joints of water-retaining structures (tanks, STPs, reservoirs, swimming pools) and water-excluding structures (basements, tunnels, retaining walls, podiums).
Why use it?
It blocks water passage through the weakest point of any concrete structure — the joint — using both a tortuous-path and valve (centre-bulb) principle, with long service-life PVC.
How is it applied?
Positioned centrally across the joint, tied to reinforcement through its eyeletted flanges, half-embedded in the first pour; the second pour encases the remaining half. Lengths are joined by heat-welding.
About Fosroc Supercast WB
Fosroc Supercast WB is a centrally-placed PVC waterstop — commonly called a “water bar” on Indian sites — designed to provide an integral sealing system for joints in concrete cast in-situ. It belongs to Fosroc’s Supercast PVC waterstop family, the same high-grade plasticised PVC compound used across the Hydrofoil and Rearguard profiles, formulated for long-term flexibility and durability in permanently buried or submerged service. The profile is extruded as a continuous ribbon with a central bulb and ribbed/eyeletted edge flanges, and is supplied in straight rolls together with factory-produced intersection pieces (Ls, Ts, crosses and equal-angle junctions) so that complex waterstop networks can be assembled with the minimum of site jointing. Every concrete structure that has to hold water in, or keep water out, is only as watertight as its joints. Concrete is poured in stages, so construction joints (cold joints between successive pours) and movement joints (expansion/contraction joints) are unavoidable, and these planes are the natural path for water under hydrostatic pressure. Supercast WB is cast straight across that plane so that the joint is bridged by a continuous, impermeable PVC barrier before the concrete is even placed. It works on two complementary principles: the long embedded width forces any seeping water along a greatly extended, tortuous path while the central bulb acts as a flexible valve that accommodates joint movement without losing the seal. In Indian construction — where sewage treatment plants, water tanks, metro tunnels, basements in high water-table cities like Kolkata and Chennai, and irrigation canals are built in huge numbers — Supercast WB is specified as the primary embedded waterproofing element, working alongside surface membranes, crystalline admixtures and joint sealants rather than replacing them. Space Arc Engineering supplies the Supercast WB range as an authorised Fosroc distributor across Delhi NCR and pan-India, with the matching welding tools, jointing guidance and complementary Fosroc waterproofing systems for a single-source joint solution.
The technical insight
Supercast WB is plasticised, high-grade PVC, not rubber or bentonite. Its performance rests on the polymer’s mechanical properties: a tensile strength of not less than 14 N/mm² and elongation at break of at least 300% (tested to BS 2782) give the profile the toughness to survive concrete placement and vibration plus the stretch to follow joint movement without tearing. A Shore A hardness in the 80–90 range balances rigidity (so the profile holds its shape during the pour) against the flexibility needed at the centre bulb. The compound is formulated against the US Army Corps of Engineers specification CRD-C 572, the long-standing benchmark for PVC waterstops, and ASTM-tested variants of the range report specific gravity around 1.32 (ASTM D792), tensile strength of roughly 16 MPa (ASTM D638) and elongation above 300%. Because the seal is mechanical and embedded — water simply cannot find a continuous path through a properly welded, properly encased profile — the system does not depend on adhesion, swelling chemistry or surface preparation, which is why correctly installed PVC waterstops last the design life of the structure. The single most important technical point is the joint between lengths: butt joints must be heat-welded (hot-knife/thermostatic welder) so the PVC fuses into one continuous piece. A poorly welded or overlapped joint is the defect that causes nearly every PVC-waterstop leak, not the profile itself.
Where it is used
- Construction joints in water-retaining structures: water tanks, clear-water reservoirs, overhead and underground tanks
- Sewage and effluent treatment plants (STP/ETP) — aeration tanks, clarifiers, sludge digesters
- Basement rafts and retaining walls in high water-table locations
- Metro, road and utility tunnels, subways and underpasses
- Swimming pools, water features and bunded chemical-containment areas
- Dams, spillways, canals, culverts and other hydraulic/irrigation works
- Podium decks, roof slabs and planters above occupied space
- Movement (expansion/contraction) joints requiring a flexible centre-bulb profile
Key advantages
- Forms a continuous, integral water seal cast directly into the joint — the primary embedded line of defence
- Wide range of profiles and widths (typically 150 mm, 200 mm, 250 mm) to suit varying hydrostatic heads and joint types
- Reinforced, eyeletted edge flanges allow positive tying to reinforcement so the profile stays put during the pour
- Tortuous-path plus central-bulb valve design resists water under pressure and accommodates movement
- Factory-made L, T, cross and angle intersection pieces cut site jointing and reduce weld-failure risk
- High-grade PVC offers excellent long-term flexibility, durability and chemical resistance when permanently buried
- Simple on-site heat-welded jointing using standard waterstop welding tools
- Cost-effective relative to remedial waterproofing of a leaking joint after the fact
Limitations & considerations
- Performance is entirely dependent on correct installation — must be held exactly central in the joint and fully encased in both pours
- Butt joints must be heat-welded; overlapping or tying lengths together is the most common cause of leaks
- Standard PVC is not suitable for continuous high-temperature service or aggressive solvents/oils — check chemical compatibility for industrial effluent
- Cannot be retrofitted — it must be designed in and cast with the structure, not added to an existing joint
- Honeycombing or poor compaction of concrete around the flanges leaves a bypass path; good vibration around the waterstop is essential
- Centrally-placed profiles need careful formwork/split-formwork detailing at the joint face
- Not a standalone waterproofing system — works with surface membranes, crystalline/integral admixtures and joint sealants, not instead of them
Selection & best practice
Position Supercast WB centrally across the joint and secure it through the eyeletted flanges to the reinforcement with tie wire at close centres so it cannot displace during pouring. Half the width is embedded in the first pour; protect the exposed half and keep it clean of concrete laitance before the second pour, which must fully encase the remaining half. Vibrate concrete thoroughly around the flanges to eliminate honeycombing — voids beside the waterstop defeat its purpose. Join straight lengths only by heat-welding with a thermostatically controlled hot plate or hot-knife; never overlap, glue or tie-wire two ends together. Use factory-fabricated intersection pieces at junctions rather than site-forming complex angles. Keep welds away from corners, and pressure-/visually inspect each weld. Always size the profile width to the hydrostatic head and select a centre-bulb (expansion) profile where genuine joint movement is expected.
Specifications
| Material | High-grade plasticised PVC (rubber/bentonite-free) |
| Profile type | Centrally-placed water bar with central bulb and eyeletted edge flanges |
| Available widths (typical) | 150 mm, 200 mm, 250 mm (range extends to larger profiles) |
| Tensile strength | Not less than 14 N/mm² (BS 2782); ~16 MPa (ASTM D638 variant) |
| Elongation at break | Not less than 300% (BS 2782) |
| Hardness | Shore A 80–90 (BS); Shore A ~76 ±3 (ASTM D2240 variant) |
| Specific gravity | ~1.32 ±0.02 (ASTM D792) |
| Specification compliance | US Army Corps of Engineers CRD-C 572-74; tested to BS 2782 |
| Jointing method | Heat-welded butt joints; factory-fabricated L/T/cross/angle intersections |
| Supply form | Continuous rolls plus prefabricated intersection pieces |
Industry use cases
Water & Wastewater
Embedded in construction joints of STP/ETP tanks, clarifiers and clear-water reservoirs to guarantee leak-free water-retaining concrete over the asset’s design life.
Infrastructure & Tunnelling
Used in metro tunnels, subways and underpasses where external hydrostatic pressure demands a continuous embedded barrier at every cold and movement joint.
Buildings & Basements
Specified for basement rafts and retaining walls in high water-table cities (Kolkata, Chennai, Mumbai) as the primary water-excluding element with surface membranes.
Irrigation & Hydraulic Works
Cast into dams, canals, culverts and spillway joints where long-term flexibility and durability under permanent submersion are critical.
Commercial & Podium
Installed at podium-deck and planter-box joints over occupied space to prevent water ingress into basements and parking below.
Frequently asked questions
What does the ‘WB’ in Fosroc Supercast WB mean?
How is Supercast WB different from Supercast SW swellable waterstops?
Does Supercast WB need to be welded at joints?
Which profile width should I specify?
Is Supercast WB a complete waterproofing system on its own?
Where can I buy Fosroc Supercast WB in India and is it available in Delhi NCR?
How we position Fosroc Supercast WB
Within the Fosroc range, Supercast WB sits alongside the Supercast Hydrofoil and XHD Hydrofoil centrally-placed profiles, the externally-placed Supercast Rearguard S, and the Supercast SW swellable waterstops — choose WB/Hydrofoil for cast-in central joints with movement, Rearguard for blinding-face external placement, and SW where a tight construction joint suits a swellable strip. It pairs naturally with Fosroc joint sealants (Thioflex 600, Nitoseal) and crystalline/integral admixtures for a complete joint and waterproofing package. Against competitors, Supercast WB is comparable to Sika’s Sika Waterbar / Sikadur waterstop range, Supreme/Kataria/Duroflex PVC waterbars widely used in India, and BASF/Master Builders Solutions Masterseal waterstops; for the swellable approach, alternatives include Sika Hydrotite, Dr. Fixit and STP (Pidilite) hydrophilic strips and bentonite waterstops. Honestly, the PVC chemistry across reputable brands is broadly similar — the real differentiators are profile quality, the availability of factory-made intersection pieces, weld integrity and installation discipline on site, which is where specifying a full Fosroc system through an authorised distributor like Space Arc Engineering adds value.
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