Fosroc Supercast SL
Blue extruded-PVC waterstop range for sealing movement and construction joints in cast-in-situ water-retaining and below-ground structures.
What is it?
Supercast SL is Fosroc’s range of centrally and externally placed PVC waterstops – flexible blue extruded thermoplastic strips cast into concrete joints to form an integral barrier against water passage, not a gun-applied or pourable sealant.
Where is it used?
Movement and construction joints in cast-in-situ water-retaining structures (reservoirs, sewage and water-treatment tanks, swimming pools, canals, spillways) and water-excluding structures (basements, car parks, tunnels, retaining walls, podium decks).
Why use it?
It provides a permanent, fully embedded waterproof seal that works on both the valve and tortuous-path principles, accommodates joint movement up to 10 mm, resists high hydrostatic head, and forms a continuous four-bulb network across wall and floor junctions.
How is it applied?
Profiles are positioned in the joint before pouring – centrally placed types wired to reinforcement via eyeletted flanges, externally placed Rearguard types nailed to shutter or laid on blinding – then concrete is fully compacted around them and lengths are joined on site by thermal heat welding.
About Fosroc Supercast SL
Fosroc Supercast SL is the company’s PVC waterstop system for sealing joints in cast-in-situ concrete. Rather than a sealant applied into a joint gap after construction, a waterstop is a continuous flexible strip that is positioned in the joint and embedded in the concrete on both sides as it is poured, so that the cured concrete grips the strip and water cannot track through the joint. The Supercast SL range is extruded from a high-grade plasticised PVC compound formulated for long-term flexibility and durability, and is supplied as straight rolls together with factory-moulded intersection and transition pieces. The strips are an unmistakable blue and carry reinforced, eyeletted edge flanges so they can be wired or nailed firmly into position before the pour. The range is built around two families: centrally placed profiles (such as the centre-bulb Hydrofoil and plain-web Watafoil sections, including heavy-duty XHD variants) that sit within the wall thickness and resist water pressure from either face, and externally placed Rearguard, Angleguard and Kicker profiles that are fixed to the shutter or laid on blinding for slabs, kicker joints and below-ground work. Across the network, Supercast SL maintains a fully continuous four-bulb design so the same waterproofing logic carries from floor slabs up into walls without a break. For Indian projects – water and sewage treatment plants, metro and tunnel works, basements, podiums and industrial containment – Space Arc Engineering supplies the Supercast SL range as an authorised Fosroc distributor and applicator, with technical support on profile selection, intersection detailing and site welding.
The technical insight
Supercast SL works on two complementary mechanisms that every specifier should understand. The first is the valve principle: the dumbbell-shaped edge bulbs are cast into adjacent concrete panels and act as anchors, so when a joint opens under shrinkage or movement the bulbs are placed in tension and seal tightly against the concrete at their inner faces. The second is the tortuous-path principle: the corrugated, multi-bulb cross-section dramatically increases the surface area and length of any potential seepage path, so water cannot find an easy route around the strip. The range’s continuous four-bulb profile delivers both effects at once. Because the compound is a true plasticised PVC (not rubber), behaviour depends on temperature – the material stiffens in cold weather, so handling, bending around intersections and heat-weld jointing all need more care below roughly 5 degrees C. Joints between lengths are made by thermal heat welding using Fosroc’s welding equipment: the cut ends are held square and aligned in a jig, pressed against a heated blade until a bead of molten PVC forms, then quickly butted together and allowed to cool into a homogeneous weld. A correctly executed weld is the single biggest determinant of in-service performance, which is why factory-produced intersection pieces are preferred at tees and crosses over improvised site fabrication.
Where it is used
- Expansion and contraction (movement) joints in water-retaining concrete, using centre-bulb Hydrofoil profiles that accommodate movement up to 10 mm
- Construction (day-work / pour) joints in walls and slabs, using plain-web Watafoil or externally placed Rearguard R profiles
- Water-retaining structures: reservoirs, water towers, clarifiers and sewage / effluent treatment tanks, canals, culverts and spillways
- Swimming pools and bunded areas surrounding liquid-retaining tanks
- Water-excluding below-ground structures: basements, underground car parks, tunnels, subways, abutments and retaining walls
- Horizontal and vertical floor-slab and foundation joints using externally placed Rearguard profiles laid on blinding or fixed to shutters
- Wall-to-kicker joints sealed with the extra-wide Rearguard Kicker profile when the kicker is cast separately from the slab
- Roof decks, podium areas and slab soffit level changes using wider movement profiles and the Angleguard transition section
Key advantages
- Permanent integral seal embedded in the concrete – works for the design life of the structure with no re-application
- Dual valve and tortuous-path sealing action from a continuous four-bulb profile for high reliability
- High hydrostatic resistance (up to around 100 m head / 10 bar on heavy-duty central profiles) suiting deep tanks and basements
- Reinforced eyeletted / nailing edge flanges give positive, tear-resistant fixing so the strip stays put during pouring
- Full range of profiles plus factory-moulded intersection and transition pieces maintains network continuity from floors into walls
- Accommodates joint movement up to 10 mm, covering typical expansion and contraction in water structures
- Suitable for use in contact with potable water (regional WRAS / WRC / AS 4020 approvals on the relevant grades)
- Heat-welded on site into homogeneous continuous lengths rather than relying on overlaps or adhesives
Limitations & considerations
- It is a waterstop, not a surface or gap-filling sealant – it must be cast into the concrete before the pour and cannot be retrofitted into a finished joint
- Performance depends almost entirely on full concrete compaction around the strip; voids or honeycombing alongside the waterstop create direct leak paths
- Site heat-weld quality is critical – a poor or contaminated weld is a weak point; factory intersections are preferred at tees and crosses
- PVC stiffens in cold weather, so handling and welding need extra care at low temperatures and cannot be done in wet or contaminated conditions
- Movement accommodation is limited (around 10 mm); very large movements need a specifically designed movement profile and joint detail
- Externally placed (Rearguard) profiles in walls only resist water pressure from the face to which they are fixed – orientation matters
- Correct width must be matched to wall thickness, rebar position and aggregate size; an over-wide strip in a thin section impairs compaction
- It addresses joints only – it is not a substitute for an integral waterproofing admixture or membrane across the wider concrete surface
Selection & best practice
Select the profile to suit the joint type and concrete section: centre-bulb Hydrofoil for movement (expansion/contraction) joints, plain-web Watafoil or Rearguard for construction joints, and heavy-duty (XHD) sections where concrete is placed from a height in deep shutters. As a rule of thumb the 250 mm width suits walls 250 mm thick and over; for thinner sections choose a narrower strip approximating the wall thickness so concrete can still be fully compacted on both sides. Centre the strip on the joint line and embed it equally in each pour. Fix positively before concreting – wire central profiles to reinforcement through the eyeletted flanges, and nail Rearguard profiles through the outer nailing flanges (leaving nail heads proud) or lay them on blinding for slabs. Keep adequate clearance to rebar so the concrete can be vibrated tight against the strip with no voids. Make all changes of direction, tees and crosses with factory-moulded intersection / transition pieces, and join straight lengths only by proper thermal heat welding with the ends cut square, clean, dry and aligned in a jig. Avoid welding in very cold, wet or dusty conditions, and protect installed waterstop from damage and displacement until the pour. Where a non-movement construction joint also needs a swellable secondary defence, Supercast SL can be combined with a hydrophilic strip from the Supercast SW range to build a layered system.
Specifications
| Product type | Extruded PVC waterstop (centrally and externally placed profiles) |
| Material | High-grade plasticised PVC thermoplastic compound |
| Form | Extruded thermoplastic sections, supplied in rolls |
| Colour | Blue |
| Tensile strength | Minimum 14 N/mm2 (BS 2782); approx 16 MPa min on AS-spec grade (ASTM D638) |
| Elongation at break | Minimum 300% (up to approx 320% on AS-spec grade) |
| Hardness | Shore A 80-90 (approx 76 +/-3 on AS-spec grade, ASTM D2240) |
| Specific gravity | Approx 1.32 (ASTM D792) |
| Hydrostatic head | Up to 100 m (10 bar) on heavy-duty central profiles; up to 60 m typical |
| Joint movement accommodated | Up to 10 mm |
| Profiles | Hydrofoil, Watafoil, XHD Hydrofoil/Watafoil (central); Rearguard S/R, Kicker, Angleguard (external) |
| Typical widths | Range up to ~250 mm standard, with ~330 mm roof movement profile (profile-dependent) |
| Compound standard | US Corps of Engineers CRD-C 572-74; BS 2782; potable-water approvals on relevant grades |
| Jointing method | On-site thermal heat welding using Fosroc welding equipment; factory-moulded intersections |
| Intersection leg length | On-flat 230 mm from centre line; on-edge 75 mm (standard) |
Industry use cases
Water & sewage treatment
Sealing expansion and construction joints in cast-in-situ clarifier tanks, aeration basins, reservoirs and water towers, where centrally placed Hydrofoil profiles resist pressure from either face and keep effluent in and groundwater out.
Metro, tunnels & infrastructure
Joint sealing in cut-and-cover tunnels, subways, station boxes and underpasses, using Rearguard external profiles against permanent shuttering to exclude groundwater under high head.
Basements & high-rise substructure
Waterproofing construction and movement joints in deep basement rafts and retaining walls of commercial and residential towers, often paired with kicker-joint Rearguard profiles at wall starts.
Industrial & containment
Bunded areas, effluent pits and liquid-retaining tanks in plants and factories where a continuous embedded barrier is required across all wall and floor joints.
Hydraulic & water resources
Canals, culverts, spillways and dam appurtenant structures where long runs of waterstop must be heat-welded into a continuous network with factory intersection pieces.
Swimming pools, podiums & roof decks
Movement joints in pool shells, podium slabs and roof decks using wider movement profiles to accommodate construction-stage and thermal movement.
Frequently asked questions
Is Fosroc Supercast SL a sealant or a waterstop?
What joints is Supercast SL used for?
How is Supercast SL jointed on site?
What hydrostatic pressure and movement can it handle?
What width of Supercast SL should I specify?
Can Supercast SL be used in potable-water and below-ground structures?
How we position Fosroc Supercast SL
Supercast SL sits in Fosroc’s joint-treatment portfolio as the cast-in PVC waterstop solution – the first line of defence built into the concrete joint itself, as opposed to the sealants that finish the visible joint gap. It is best understood alongside, not in place of, Fosroc’s gap-filling sealants: Nitoseal (polyurethane) and Thioflex 600 (polysulphide) for general movement and construction joints, and Colpor 200PF for heavy-duty trafficked and pavement joints. On many water and below-ground projects these are used together – Supercast SL embedded to stop water through the joint, with a surface sealant completing the joint face – and for non-movement construction joints it can be combined with the hydrophilic Supercast SW swellable range for a layered seal. Among comparable PVC and waterproofing waterstop systems available in India, credible alternatives include Sika’s PVC waterstops and SikaSwell hydrophilic profiles, MBS (Master Builders Solutions) MasterSeal / MasterFlex waterstops, and STP (Supreme / domestic) PVC waterstop ranges. Space Arc Engineering positions Supercast SL where its proven four-bulb profile range, factory intersection pieces and Fosroc’s specification support give consultants and contractors a well-detailed, well-supported waterstop network – backed locally by an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India.
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