Fosroc Supercast SW Adhesive
Gun-applied elastomeric bonding paste for fixing Supercast SW hydrophilic swellable waterstops to concrete construction joints, even on damp substrates.
What is it?
A grey, single-component, gun-applied elastomeric paste from Fosroc used to bond Supercast SW hydrophilic (water-swellable) waterstop sections onto concrete. It is an installation accessory within the Supercast SW swellable-waterstop system, not a movement-joint sealant.
Where is it used?
Non-movement construction (day-work) joints in water-retaining and below-ground in-situ concrete: basement rafts and walls, pile caps, secant-pile and diaphragm-wall interfaces, water tanks, STPs/ETPs, pipe-entry detailing and casting against existing concrete.
Why use it?
It holds the swellable waterstop firmly in correct position during reinforcement fixing and concrete placement, bonds reliably to damp concrete, and avoids the mechanical pinning, nailing or complex shuttering that conventional PVC/rubber waterstops demand.
How is it applied?
Gunned as a continuous bead from a cartridge onto sound, debris-free concrete; the Supercast SW strip is pressed firmly into the wet bead and held until grip develops, then the joint is reinforced and the next concrete pour cast around it.
About Fosroc Supercast SW Adhesive
Fosroc Supercast SW Adhesive is a purpose-made bonding paste within Fosroc’s Supercast SW range of swellable (hydrophilic) waterstops. Its single job is to fix Supercast SW formed waterstop sections securely to a hardened concrete surface so they stay in the right place while reinforcement is fixed and the next lift of concrete is poured around them. It is a grey, single-component, gun-applied elastomeric paste, supplied in cartridge form and applied with a standard skeleton or sausage gun, which makes it fast to use on site without specialist equipment.
It is important to understand what this product is and is not. It is not a polyurethane, polysulphide, silicone or MS-polymer movement-joint sealant of the Nitoseal, Thioflex or Colpor type, and it carries no movement accommodation factor (MAF), no ISO 11600 or ASTM C920 sealant classification, and no primer schedule. It belongs to the waterstop family. The Supercast SW system works on a hydrophilic principle: the waterstop strip contains hydrophilic groups bound into a synthetic-elastomer structure, so when groundwater reaches the cast-in strip it swells, by up to roughly 200% of its original volume, and presses outward against the two concrete faces of the joint. That positive pressure closes the capillary path and stops water tracking through the construction joint. The adhesive simply guarantees the strip is in intimate, continuous contact with the concrete before that swelling mechanism is ever called upon.
A practical strength of the adhesive is that it can be applied to damp substrates, which is realistic for the wet, below-ground environments where swellable waterstops are specified. It also tolerates minor surface irregularities in the concrete, filling small voids so the swellable strip seats evenly. Within the wider Supercast SW system the closely related Supercast SWX, a grey gun-applied swellable paste, performs both as a bonding medium and as a swellable jointing compound that links Supercast SW into conventional Supercast PVC waterstop networks; the SW Adhesive is the dedicated, economical fixing option where you simply need to stick the formed section down. For Indian contractors, consultants and waterproofing applicators, Space Arc Engineering supplies the complete Supercast SW system, Adhesive, SWX paste and SW10/SW20 formed sections, as an authorised Fosroc distributor across Delhi NCR and Pan-India.
The technical insight
The most common specification error is treating Supercast SW Adhesive as a structural seal. It is not. In a Supercast SW joint the seal is produced entirely by the hydrophilic waterstop swelling under groundwater contact and generating confined pressure against the concrete; the adhesive’s structural contribution is effectively zero. Its role is positional, keeping the strip exactly where the designer intended through rebar fixing and the concrete pour. This has two design consequences. First, adequate concrete cover over the strip is essential to confine the swelling pressure rather than spall the cover, Fosroc cites a minimum cover of 75 mm for Supercast SW10 and 80 mm for SW20, so the adhesive should run the strip along the joint centreline with that cover maintained on both faces. Second, pre-swell is the real enemy: if the strip is wetted and swells before the concrete is cast it loses the positive pressure it should have built inside fresh concrete, so SW10/SW20 use a delayed-swell formulation and the strip (and adhesive) should be installed as close as practicable to the pour and protected from standing water. Continuity also matters more than adhesion strength, the bead must be unbroken and the strip butted/lapped per Fosroc’s detail so there is no bypass path; the adhesive’s damp-tolerance is what makes that continuity achievable on a genuinely wet basement face.
Where it is used
- Fixing Supercast SW10/SW20 swellable waterstops along horizontal construction (kicker/day-work) joints in basement rafts and slabs
- Bonding swellable strips to vertical wall construction joints where shuttering a conventional waterstop would be impractical
- Sealing pipe and service penetrations through water-retaining and below-ground concrete
- Casting new concrete against existing/old concrete, e.g. extensions to existing water structures
- Secant-piled and diaphragm-walled basement interfaces where the strip is bonded to the pile/wall face before the lining wall is cast
- Pile caps and ground beams requiring a non-movement joint seal
- Water tanks, sumps, lift pits, retaining walls, water and sewage treatment (STP/ETP) structures
- Detailing complex joint geometries in conjunction with Supercast SWX and Supercast PVC waterstop networks
Key advantages
- Single-component, gun-applied paste, fast to install with a standard skeleton/sausage gun and no specialist plant
- Can be applied to damp substrates, suited to the wet below-ground conditions where swellable waterstops are used
- Holds Supercast SW sections firmly in position during rebar fixing and concrete placement, reducing displacement defects
- Fills minor concrete surface irregularities so the swellable strip seats in continuous contact
- Avoids the complex shuttering, split formwork and mechanical fixing associated with conventional PVC/rubber waterstops
- Part of a coordinated Fosroc system, integrates with Supercast SWX paste and Supercast SW10/SW20 sections and links to Supercast PVC networks
- Supports detailing of difficult joints, pipe entries, vertical joints and casting against old concrete
- No mixing, no primer schedule and minimal training required for application crews
Limitations & considerations
- Not a movement-joint sealant, it has no movement accommodation factor and must not be used to seal expansion or significant movement joints
- Suitable only for non-movement construction joints; for moving joints use a graded sealant (Nitoseal / Thioflex / Colpor)
- An installation accessory only, the waterproofing seal is provided by the swellable waterstop, not by the adhesive
- Depends on adequate concrete cover (min ~75 mm for SW10, ~80 mm for SW20) to confine swelling pressure, the adhesive cannot compensate for thin cover
- Vulnerable to pre-swell, the bonded strip must be protected from standing water and cast in promptly to preserve positive sealing pressure
- Requires a sound, reasonably clean substrate, it will not bond reliably to loose laitance, dust, oil or curing-compound residue
- Has a limited open time, the strip must be positioned before the bead skins; application temperature should be kept within the manufacturer’s stated range
- Not a standalone product, performance is only meaningful as part of a correctly detailed Supercast SW system
Selection & best practice
Treat the adhesive as a positioning aid, not a seal. Prepare the joint face first: remove laitance, dust, oil and curing residues and expose sound, clean concrete, the surface may be damp but should not have standing water. Run a continuous, unbroken bead of Supercast SW Adhesive along the joint centreline, then press the Supercast SW strip firmly into the wet bead and hold it until initial grip develops, butting or lapping section ends per Fosroc’s detail so there is no bypass path. Maintain the required concrete cover on both faces (minimum ~75 mm for SW10, ~80 mm for SW20) to confine the swelling pressure. Protect the bonded strip from rainfall and standing water and cast the next lift as soon as practical to avoid pre-swell; use the delayed-swell SW10/SW20 sections in wet conditions. Where the swellable run must integrate with PVC waterstops or needs a swellable jointing compound, use Supercast SWX rather than the Adhesive. Always follow the current Fosroc method statement and product datasheet, and confirm pack size, coverage and temperature limits against the supplied label as these vary by region and pack format.
Specifications
| Product type | Single-component gun-applied elastomeric bonding paste (accessory within the Supercast SW swellable waterstop range) |
| Primary function | Bonds Supercast SW hydrophilic swellable waterstop sections to concrete |
| Sealing mechanism (system) | Hydrophilic, waterstop swells up to ~200% on water contact to seal the joint (adhesive itself is non-sealing) |
| Colour | Grey |
| Substrate condition | Sound concrete; can be applied to damp substrates |
| Application | Gun-applied (skeleton / sausage gun); no mixing |
| Joint suitability | Non-movement construction joints only (not for movement/expansion joints) |
| Concrete cover (system requirement) | Min. 75 mm for Supercast SW10; min. 80 mm for Supercast SW20 |
| Primer | Not required |
| Movement accommodation factor | Not applicable (not a movement-joint sealant) |
| Related system products | Supercast SWX (swellable paste), Supercast SW10 / SW20 formed sections, Supercast PVC waterstops |
| Manufacturer | Fosroc International |
| Pack / coverage / shelf life | Cartridge format; coverage depends on bead diameter (e.g. distributor data ~3.4 m run per cartridge at 12 mm bead). Confirm exact pack size, coverage and shelf life against current Fosroc datasheet/label for the supplied region |
Industry use cases
Below-ground / basements
Bonding swellable waterstops to secant-pile, diaphragm-wall and raft-to-wall construction joints in deep basements where conventional waterstop shuttering is impractical.
Water & wastewater (STP/ETP, tanks)
Sealing non-movement construction joints in water tanks, sumps, treatment-plant structures and reservoirs where a hydrophilic strip must stay positioned until cast in.
Infrastructure & metro
Construction-joint waterstopping in cut-and-cover boxes, underground stations and tunnels, including pipe-entry and service-penetration detailing.
Building podiums & lift pits
Fixing swellable strips to kicker and day-work joints in podium slabs, retaining walls, lift pits and ground beams to control groundwater ingress.
Repair & extension works
Casting new water-retaining concrete against existing/old concrete, where the strip is bonded to the prepared old face before the new pour.
Frequently asked questions
Is Fosroc Supercast SW Adhesive a joint sealant?
Can it be applied to damp concrete?
What is the difference between Supercast SW Adhesive and Supercast SWX?
Does it need a primer?
How much concrete cover is needed over the waterstop?
Where can I buy Fosroc Supercast SW Adhesive in India?
How we position Fosroc Supercast SW Adhesive
Supercast SW Adhesive sits firmly in the swellable-waterstop accessory category, not the movement-joint sealant category, and it should be specified accordingly. Within the Fosroc range it pairs with Supercast SW10/SW20 formed sections and the more versatile Supercast SWX paste (which additionally links to Supercast PVC waterstop networks), so on most projects you will specify these together rather than in isolation. It does not compete with Fosroc’s gun-grade and pouring-grade movement sealants, Nitoseal (polyurethane/MS), Thioflex 600 (polysulphide) and Colpor 200PF (pavement-grade), which carry movement accommodation factors and ISO 11600 / BS classifications and are the correct choice for expansion and movement joints; SW Adhesive deliberately has no MAF because it serves non-movement construction joints. For the swellable-waterstop function itself, credible alternatives that engineers may encounter include Sika’s hydrophilic profiles and adhesives (SikaSwell range), BASF/Master Builders Solutions MasterSeal swellable/waterstop products, and STP (Supreme/Choksey-type) hydrophilic waterstops in the Indian market. As an authorised Fosroc distributor and applicator in Delhi NCR and Pan-India, Space Arc Engineering can supply the matched Supercast SW system and advise on whether a swellable waterstop, a PVC waterstop or a graded movement sealant is the right specification for a given joint, ensuring the adhesive is used only where it genuinely belongs.
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