Sika SikaSwell
A hydrophilic swelling profile-and-sealant system that seals concrete construction joints from the inside, expanding on contact with water to shut off seepage paths.
What is it?
A two-part hydrophilic waterstop system: SikaSwell A, an acrylic swelling profile, and SikaSwell S-2, a one-part polyurethane swelling sealant that both bonds the profile and works as a stand-alone bead.
Where is it used?
Construction (day-work) joints and penetrations in watertight concrete — basement rafts and walls, water tanks, STPs, tunnels, pits and pipe entries.
Why use it?
It expands against the joint faces when wet, generating sealing pressure that rises with water pressure, so a single strip closes the joint without embedding a bulky dumbbell waterstop.
How is it applied?
S-2 is gunned as a triangular bead onto the cleaned first-pour face; the A profile is pressed in within 30 minutes, left to harden, then cast over by the second pour.
About Sika SikaSwell
SikaSwell is Sika’s hydrophilic joint-sealing system for watertight concrete, and it is best understood as two products that work together. SikaSwell A is a rectangular acrylic profile that is fixed along the face of a construction joint; SikaSwell S-2 is a one-part, moisture-curing polyurethane that acts as the adhesive bedding for that profile and can also be run as a stand-alone swelling bead where a formed strip is awkward to place. Both are hydrophilic — they draw in water and swell — so instead of relying on a physical labyrinth like a PVC dumbbell waterstop, the seal is created by controlled expansion that presses tightly against both concrete faces of the joint.
For engineers and contractors in India, the appeal is practical. Construction joints between successive concrete pours are the classic weak point in basements, tanks, sewage works and tunnels, and threading a conventional waterstop through congested reinforcement is slow and easy to get wrong. A SikaSwell strip is simply glued to the hardened first-pour face on the centre-line of the section and cast over, which cuts installation labour and suits heavily reinforced or thin elements where a full-cross-section waterstop will not fit. Space Arc Engineering supplies the profiles and sealant and, as an applicator, can set out the joint detailing, cover and pour sequence so the system performs as intended on site.
The technical insight
The mechanism is osmotic swelling, not chemical curing of a barrier. SikaSwell A is built on an acrylic polymer and SikaSwell S-2 on a moisture-cured polyurethane; both carry hydrophilic groups bound into the polymer chain, so when water reaches the joint the material absorbs it and increases in volume. Per Sika’s EN 14498 data the S-2 sealant grows by roughly 25 percent at one day, 100 percent at seven days and about 200 percent at thirty days in demineralised water, while the A profile reaches roughly 50, 130 and 150 percent over the same intervals. Because the profile sits confined at the centre of a dense concrete section, that volume increase has nowhere to go and instead converts into contact pressure — in a sound structure the swelling pressure can exceed 10 bar, and crucially it self-adjusts: the more water pressure the joint sees, the harder the strip presses back, which lets it chase and close small cracks and voids at the interface. The swelling is deliberately delayed by a few hours rather than instantaneous, so the strip does not pre-expand from ambient site humidity or light rain before the covering concrete is placed, and the reaction is reversible — if the joint dries the material shrinks back and re-swells on the next wetting cycle. That reversibility is what gives it durability through repeated wet-and-dry service rather than a one-shot seal.
Where it is used
- Sealing horizontal and vertical construction joints in basement rafts, retaining walls and water-retaining slabs
- Waterproofing pipe, conduit and steelwork penetrations through concrete walls and floor slabs
- Construction joints in water storage tanks, sumps and clear-water reservoirs
- Joints in sewage treatment plant tanks, effluent channels and process structures
- Lining and invert construction joints in road, rail and utility tunnels
- Cable-duct and service-trench construction joints
- Casting new watertight concrete against existing or old concrete
- Congested or thin sections where embedding a full-cross-section dumbbell waterstop is impractical
Key advantages
- Active seal — swelling pressure rises with water pressure, so the joint self-tightens against leakage
- Faster and cheaper to install than PVC dumbbell waterstop; the strip is simply bonded to the joint face, with no wire-tying to rebar
- Fills small cracks, voids and surface irregularities at the joint interface as it expands
- Delayed swelling prevents premature expansion from site humidity or light rain before the second pour
- Permanently water-resistant through repeated wet-and-dry cycles; shrinks and re-swells rather than failing
- Compact profiles (20 mm wide) suit heavily reinforced and thin sections without adding congestion
- S-2 works two ways — as the adhesive for the profile and as a stand-alone swelling bead for irregular details
- BBA-approved system (SikaSwell A-2010 with S-2) with independent watertightness testing, and LEED-conforming
Limitations & considerations
- Not for movement or expansion joints — it seals static construction joints only; use a proper expansion-joint waterstop or sealant there
- Recommended for hydrostatic pressures up to about 2 bar; beyond that use an alternative or a supplementary Sika joint-sealing solution
- Performance depends on adequate, dense concrete cover — a minimum of 75 mm each side in reinforced concrete (150 mm unreinforced); low-density concrete, honeycombing or voids will stop it working
- Swelling in saline or brackish water is reduced and delayed — a dedicated maritime-grade profile is required for marine exposure
- Swelling is not instantaneous, so it should not be relied on to seal a joint that already has standing water at the time of the pour
- The S-2 sealant has a relatively short shelf life (about 9 months) and must be protected from water and cast over within the specified window
Selection & best practice
Set the strip out on the centre-line of the section so it stays confined, and keep the minimum concrete cover — 75 mm each side in reinforced sections, 150 mm in unreinforced. The first-pour face must be sound, clean and dry or only matt-damp; level rough or honeycombed concrete with S-2 or a Sika levelling mortar first, because a rough face leaks. Apply SikaSwell S-2 as a continuous triangular bead (about 12 mm section) and press the SikaSwell A profile firmly into the wet adhesive within 30 minutes, ensuring full, unbroken contact along both the profile and the substrate with no gaps at overlaps. Allow the S-2 to harden for at least 12 hours before casting the next lift — 24 hours where the pour height exceeds 50 cm — and protect it from rain or standing water in the meantime so it does not swell early. When placing the covering concrete, compact it thoroughly around the strip to achieve dense, void-free concrete. On tight-tolerance or high-risk structures, use SikaSwell as a second line of defence alongside a Sika PVC waterbar rather than as the sole barrier.
Specifications
| Product type | Hydrophilic swellable waterstop system — SikaSwell A (acrylic profile) + SikaSwell S-2 (1-part PU sealant/adhesive) |
| Chemical base | A profile: acrylic polymer. S-2 sealant: 1-part moisture-curing polyurethane |
| Profile sizes (SikaSwell A) | A-2005: 20 x 5 mm (20 m/roll); A-2010: 20 x 10 mm (10 m/roll); A-2025: 20 x 25 mm (5 m/roll) |
| Volume swell — S-2 (demin. water, EN 14498) | ~25% at 1 day, ~100% at 7 days, ~200% at 30 days |
| Volume swell — A profile (demin. water, EN 14498) | ~50% at 1 day, ~130% at 7 days, ~150% at 30 days |
| Swelling pressure | Up to >10 bar in a sound concrete structure |
| Sealing capacity | Recommended for water pressures up to 2 bar |
| Density | A profile 1.50 kg/l; S-2 sealant 1.24 kg/l (at +23 °C) |
| S-2 packaging / handling | 300 ml cartridges (12/box) and 600 ml unipacks (20/box); skin ~60 min; harden 12 h before pour (24 h if pour height >50 cm) |
Industry use cases
Basements & podiums
Sealing raft-to-wall and wall lift construction joints in deep basements and podium tanks where reinforcement is too congested for a conventional dumbbell waterstop.
Water & wastewater
Watertight construction joints in clear-water reservoirs, ESRs, STP tanks and effluent channels, where the reversible wet-dry swelling suits fluctuating liquid levels.
Tunnels & infrastructure
Lining and invert construction joints in road, rail and utility tunnels, and cable-duct joints, where a low-profile strip is easier to place than a formed waterbar.
Penetration sealing
Ring-sealing pipe, sleeve and steelwork penetrations through walls and slabs using S-2 as a stand-alone swelling bead around the profile.
Repair & extension
Casting new watertight concrete against existing or old concrete, where the strip bonds to the prepared old face and seals the cold joint.
Frequently asked questions
Is SikaSwell a replacement for a PVC waterstop?
What is the difference between SikaSwell A and SikaSwell S-2?
How much SikaSwell S-2 do I need per metre of joint?
What concrete cover does SikaSwell need to work?
How long before I can pour the covering concrete?
Does it still work if the joint dries out between wet seasons?
How we position Sika SikaSwell
SikaSwell is the swellable-strip option within Sika’s construction-joint waterproofing family. Where the design calls for a physical barrier waterstop, pair or compare it with Sika Waterbar (PVC dumbbell and centre-bulb waterstops) for the main joints, and use SikaSwell S-2 for penetration ring-seals and awkward details. For the wider watertight-concrete package, Space Arc typically specifies it alongside Sika crystalline or membrane systems and Sikadur / SikaGrout products for adjacent repair and anchoring work. Against our other brands, it competes directly with Fosroc’s Supercast SW hydrophilic waterstop range and Dr. Fixit / STP swellable strips; the choice usually comes down to the approved specification on the project and availability, and our team can match the correct grade to the joint detail and hydrostatic head.
Fosroc Supercast SW — A specifier standardised on a Fosroc waterproofing package, or one who wants the swellable waterstop and its adhesive from the same house as the rest of the joint system, may prefer Supercast SW as the direct hydrophilic-strip equivalent.
Related Sealants & Joint Treatment products
Source Sika SikaSwell for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.