Fosroc Supercast SW30
High-swell hydrophilic waterstop strip that expands up to 500% to self-seal non-movement concrete construction joints against 100 m of hydraulic head.
What is it?
A high-performance synthetic-elastomer hydrophilic (water-swellable) waterstop strip that expands on contact with water to seal in-situ concrete construction joints. It is the high-swell member of the Fosroc Supercast SW family, sitting above SW10 and SW20.
Where is it used?
Non-movement construction (day-work) joints in water-retaining and below-ground concrete: basement rafts and walls, secant-pile and diaphragm-wall basements, pile caps, lift pits, water tanks, STPs/ETPs, tunnels and pipe penetrations.
Why use it?
It self-seals joints and minor surface undulations without complex shuttering, tolerates salts in concrete and saline groundwater, keeps performing through repeated wet/dry cycling, and links into Supercast PVC networks for a continuous waterproofing system.
How is it applied?
Bonded to clean, sound, damp-tolerant concrete along the centre-line of the joint using Supercast SWX swellable paste or Supercast SW Adhesive (minimum 12 mm bead), or cast into a formed groove, then the second concrete pour is placed over it with adequate cover.
About Fosroc Supercast SW30
Fosroc Supercast SW30 is a hydrophilic, water-swellable waterstop supplied as a preformed rectangular elastomer strip. It belongs to the Fosroc Supercast SW range of swellable waterstops, which also includes the lower-swell SW10 and SW20 grades, plus the companion Supercast SWX gun-grade paste and Supercast SW Adhesive used to bond and link the strips. SW30 is the high-swell grade: where SW10 and SW20 expand up to around 200%, SW30 is rated to increase in volume by up to 500% on contact with water, which lets a single strip self-seal joint gaps and surface irregularities of up to about 2 mm and resist a hydrostatic head of up to 100 metres in a properly detailed, restrained construction joint. The swelling action comes from hydrophilic groups built into the polymer’s molecular structure rather than from a bentonite or rubber-bentonite filler; because these groups are an intimate part of the polymer, they are not leached out and the strip keeps swelling reliably through repeated wet and dry cycles over the life of the structure. Unlike movement-accommodating gun-grade sealants such as Fosroc Nitoseal or Thioflex, SW30 is not a sealant for moving expansion joints, it is a passive sealing strip for non-movement joints where two concrete pours meet. For specifiers and contractors in India working on basements, water tanks, treatment plants and tunnels, SW30 is a clean, fast-to-install alternative to traditional centre-bulb PVC waterstops that would otherwise need careful shuttering and positioning during the first pour, and it integrates with Supercast PVC waterstops via Supercast SWX so a single project can mix swellable strips at construction joints with PVC waterstops at expansion joints while keeping the network continuous. Space Arc Engineering supplies Supercast SW30 as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, with site-level guidance on joint detailing, adhesive selection and concrete cover.
The technical insight
The performance of a hydrophilic strip like SW30 is governed by confinement, not by raw swell percentage. When the second pour cures around the strip, swelling is restrained, so instead of simply getting bigger the strip develops a positive contact pressure against both faces of the joint, and it is that pressure (not the volume change) that blocks water. Two practical consequences follow. First, adequate concrete cover is essential: the surrounding concrete must be thick enough to contain the swelling pressure without cracking or spalling, which is why the range specifies a minimum cover of roughly 75-100 mm (SW10 75 mm, SW20 80 mm, and SW30 the highest because it is the highest-swell grade). Second, the strip must never be allowed to pre-swell before it is encapsulated, hence the delayed-swell behaviour engineered into the SW family and the rule that the strip must not be immersed in water before the concrete is placed. Swell rate is also a function of water chemistry and temperature: colder water and higher dissolved-solids (saline) content slow the swell down, which is actually an advantage on Indian coastal and high-water-table sites because it reduces the risk of premature swelling while still delivering a durable seal. SW30’s 500% capacity gives it the working margin to seal larger surface undulations and the higher 100 m head rating, making it the grade of choice for Grade 3 (BS 8102) basements and deep, high-pressure conditions.
Where it is used
- Construction (day-work) joints in in-situ reinforced concrete rafts, walls and slabs
- Secant-piled and diaphragm-walled basements, including Grade 3 (habitable, dry) basements
- Pile caps and casting fresh concrete against existing/old concrete
- Lift pits, sump pits and below-ground service chambers
- Water-retaining structures: clear-water tanks, reservoirs, ESRs/UGRs, swimming pools
- Sewage and effluent treatment plants (STP/ETP) and other water/wastewater structures
- Pipe and service penetrations through concrete walls and slabs
- Vertical-plane construction joints and kicker joints
- Tunnels, metro and other deep below-ground works in high-water-table or saline ground
- Linking into Supercast PVC waterstop networks (via Supercast SWX) for combined construction + expansion joint systems
Key advantages
- Very high swell capacity (up to 500%) self-seals joint gaps and surface undulations up to ~2 mm
- Resists high hydrostatic head (up to 100 m) in restrained, non-movement joints
- Hydrophilic groups are part of the polymer, so swelling is not lost through repeated wet/dry cycling
- Far simpler and faster to install than centre-bulb PVC waterstops, no special first-pour shuttering
- Bonds to damp substrates using Supercast SWX or Supercast SW Adhesive, suiting real site conditions
- Tolerant of salts in the concrete and in saline groundwater, ideal for coastal and high-TDS sites
- Delayed-swell action reduces premature swelling during wet site conditions
- Integrates with Supercast PVC networks for continuous mixed construction/expansion joint waterproofing
- Highly adaptable around complex joint shapes, pipe entries and congested reinforcement
- Free of rubber and bentonite inclusions, avoiding the wash-out concerns of some bentonite strips
Limitations & considerations
- Not a sealant and not for expansion or moving joints, it suits only non-movement joints with movement under ~2 mm
- Requires adequate concrete cover (high-swell grades need around 100 mm) to contain swell pressure without cracking the concrete
- Must not be immersed or allowed to pre-swell before the second concrete pour is placed
- Swell rate slows in cold and in high-solids/saline water, affecting early sealing speed
- Should not be used where swelling is free and unrestrained, e.g. free-standing bund or dwarf walls, as swell pressure can lift the wall
- Needs sound, reasonably clean concrete and the correct adhesive (Supercast SWX on rough concrete, minimum 12 mm bead) for reliable bond
- Performance depends on correct centre-line positioning and continuity of the strip and its laps
- Not a substitute for a properly designed and compacted, low-permeability concrete mix
Selection & best practice
Treat SW30 as a confined-pressure seal, not just a swelling strip. Design the joint so the strip sits near the centre of the section with a minimum of about 100 mm concrete cover on each side to safely contain the swell pressure; on thin sections drop to SW20 or consult Fosroc rather than risk spalling. Prepare the first-pour face so it is sound, free of laitance, loose material and curing compound, then run a continuous bead of Supercast SW Adhesive on smooth concrete or Supercast SWX on rough concrete (12 mm minimum bead diameter) and press the strip firmly along the joint centre-line, butting ends tightly. Keep the strip dry and protected from rain and standing water until the second pour is cast, because pre-swelling before encapsulation wastes its capacity. Where the construction joint meets a PVC waterstop at an expansion joint, link the two with Supercast SWX to keep the network continuous. Because SW30 cannot accommodate movement, reserve it for non-movement construction joints and detail genuine expansion/movement joints with a movement waterstop or a gun-grade movement sealant such as Fosroc Nitoseal or Thioflex.
Specifications
| Product type | Hydrophilic (water-swellable) waterstop, preformed elastomer strip |
| Chemistry | High-performance synthetic elastomer with intimately bound hydrophilic groups (no rubber/bentonite inclusions) |
| Grade / family | High-swell grade of the Fosroc Supercast SW range (above SW10 and SW20) |
| Form | Rectangular-section elastomeric strip (supplied in rolls) |
| Unrestrained volumetric swell | Up to 500% |
| Self-seals joint gaps up to | ~2 mm (with Supercast SWX / SW Adhesive) |
| Hydrostatic head resistance | Up to 100 metres (non-movement construction joint) |
| Solids content | 100% |
| Minimum concrete cover | ~100 mm (high-swell grade; SW10 75 mm / SW20 80 mm for comparison) |
| Bonding adhesive | Supercast SWX swellable paste (rough concrete) or Supercast SW Adhesive (smooth); 12 mm min bead |
| Compatibility | Links into Supercast PVC waterstop networks via Supercast SWX |
| Suitable for | Non-movement construction joints; movement up to ~2 mm only |
| Environment | Tolerant of salts in concrete and saline groundwater |
| Application | Bond to (damp-tolerant) concrete or cast into a formed groove |
Industry use cases
Basements & deep substructure
Sealing construction joints in secant-pile and diaphragm-wall basements and Grade 3 (habitable) basements where high swell capacity and 100 m head rating are needed.
Water-retaining structures
Day-work joints in clear-water tanks, reservoirs, ESRs/UGRs and swimming pools, where a clean swellable strip avoids complex PVC waterstop shuttering.
Water & wastewater treatment
Construction joints in STP/ETP tanks and channels, including sites with saline or high-TDS effluent where SW30 stays effective.
Infrastructure & tunnelling
Joints and pipe penetrations in metro, tunnel and below-ground utility works in high-water-table or coastal saline ground.
Industrial & precast-to-insitu
Casting new concrete against existing/old concrete at pile caps, lift pits and chambers, sealing the cold joint between the two pours.
Combined waterstop systems
Projects mixing PVC waterstops at expansion joints with SW30 at construction joints, linked through Supercast SWX for a continuous network.
Frequently asked questions
Is Fosroc Supercast SW30 a sealant or a waterstop?
How much does Supercast SW30 swell, and how much water pressure does it resist?
What is the difference between Supercast SW10, SW20 and SW30?
How is Supercast SW30 installed?
Can SW30 be used at expansion or movement joints?
Does it work in saline ground and damp conditions common on Indian sites?
How we position Fosroc Supercast SW30
Within the Fosroc joint-treatment range, Supercast SW30 sits in the swellable-waterstop family, distinct from Fosroc’s gun-grade movement sealants. Use SW30 (or its lower-swell siblings SW10/SW20) for non-movement construction joints, and reach for Fosroc Nitoseal (polyurethane/MS), Thioflex 600 (polysulphide) or Colpor 200PF (pour-grade, for trafficked movement joints) when the joint genuinely moves and needs an elastomeric sealant. SW30 also pairs with Supercast PVC waterstops (via Supercast SWX) so a project can run swellable strips at construction joints and PVC at expansion joints in one continuous network. Among credible alternatives on Indian projects, comparable hydrophilic/swellable waterstops include Sika Hydrotite / SikaSwell profiles and pastes, MBCC/Master Builders Solutions MasterSeal swellable and PVC waterstop systems, and STP Hydroseal-type swellable strips; the right choice usually comes down to specified swell ratio, head rating, available concrete cover and whether the detail must tie into an existing PVC waterstop network. Space Arc Engineering, as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, supplies Supercast SW30 with the matching SWX/SW adhesives and joint-detailing support.
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