Fosroc Nitofill WS60
A fast-reacting two-part polyurethane injection resin that meets moving water head-on, foaming inside the crack to shut off active leaks in seconds.
What is it?
A two-part liquid polyurethane crack-injection resin from Fosroc that reacts on contact with water to form a rigid, water-resistant foam barrier inside the crack.
Where is it used?
Cracked and leaking concrete under hydrostatic pressure: basements, water-retaining structures, tunnels, lift pits, retaining walls and construction joints where water is actively flowing.
Why use it?
It stops gushing water almost immediately, buying you a dry working face so a permanent flexible seal can then be injected. Its very low viscosity lets it travel deep into fine cracks before it foams.
How is it applied?
Mixed in the supplied proportions and pressure-injected through packers with a single- or two-component PU pump; the resin expands and cures where it meets water in the crack.
About Fosroc Nitofill WS60
Nitofill WS60 is Fosroc’s answer to one of the most stubborn problems on a repair site: a crack that will not stop weeping long enough for you to seal it. It is a two-part liquid polyurethane, mixed in the ratio supplied, that is injected into the crack under pressure. The moment the resin meets water it reacts, expanding and curing into a dense, rigid foam that physically blocks the flow path. Reaction is quick, typically between 5 and 30 seconds depending on temperature, so even a live, pressurised leak can be arrested rather than chased around the structure. This makes WS60 primarily a water-stopping, or “curtain”, resin rather than a final structural filler.
Because the resin is very low in viscosity, around 2 to 3 poise at 20 degrees Celsius, it penetrates well into hairline and moderate cracks, roughly 0.2 mm to 5 mm wide, before the foaming reaction takes hold. The cured foam resists water, weak acids and alkalis, mineral oils, ground and sea water, petroleum products, and biological attack from fungus and bacteria, which is why it holds up in basements, sumps and water-retaining structures. In practice WS60 is used as the first stage of a two-stage repair: it dries the crack out, and Fosroc Nitofill UR63 or a suitable epoxy is then injected behind it to deliver the permanent, more flexible or structural seal. For engineers in Delhi NCR and across India dealing with monsoon-season ingress, that “stop it now, seal it properly next” sequence is exactly the workflow WS60 is built for.
The technical insight
The chemistry is deliberately water-triggered. WS60 is a polyurethane pre-polymer that stays liquid and stable in the absence of moisture, with a pot life of 6 to 8 hours at 20 degrees Celsius, giving crews a realistic working window. Introduce water and the isocyanate groups react vigorously, releasing gas that drives expansion and simultaneously cross-linking the resin into a closed rigid foam. That single reaction does two useful jobs at once: the gas expansion pushes the resin into side branches and voids of the crack the pump alone could never reach, while the rapid cure locks the mass in place before the flowing water can wash it out. The foam density is low, around 0.025, so a modest volume of resin fills a disproportionately large void. The trade-off is that a rigid foam is a hydraulic plug, not a movement-accommodating gasket, which is why WS60 is specified to arrest flow and dry the substrate, with a more flexible resin following behind for the long-term seal.
Where it is used
- Stopping active, pressurised water leaks through cracks in basement walls and floors
- Sealing leaking construction and movement joints in water-retaining and below-grade structures
- Curtain injection behind tunnel linings and segmental joints to arrest ingress
- Drying out lift pits, sumps, sewage and water-treatment tanks before permanent repair
- First-stage water-stop in retaining walls, diaphragm walls and basement rafts
- Emergency control of gushing leaks during monsoon or dewatering works
- Pre-injection of wet cracks ahead of an epoxy or flexible PU permanent seal
- Sealing cracks in dams, reservoirs and hydraulic structures under standing head
Key advantages
- Reacts with water in as little as 5 to 30 seconds, so it stops even fast-flowing leaks
- Very low viscosity (2 to 3 poise at 20 degrees Celsius) lets it penetrate fine cracks deeply
- Expands into a rigid closed foam that fills voids the pump cannot reach directly
- Cured foam resists water, weak acids and alkalis, oils, sea water and microbial attack
- Generous 6 to 8 hour pot life at 20 degrees Celsius gives crews a workable mixing window
- Effective on damp and actively leaking substrates where many resins fail to bond
- Works as the ideal first stage before a Nitofill UR63 or epoxy permanent seal
- Backed by Fosroc’s established injection system of packers, pumps and companion resins
Limitations & considerations
- It is a water-stop, not a structural or flexible final seal; a follow-up resin is usually needed
- The cured foam is rigid, so it does not accommodate ongoing crack movement on its own
- Very fast reaction demands trained operators and proper packer spacing to avoid blocked ports
- Being a two-part system, it must be mixed correctly; careless proportioning affects cure
- Best suited to cracks roughly 0.2 mm to 5 mm; very fine or very wide gaps need other solutions
- Requires a suitable PU injection pump and packers, not a hand-caulked or trowel-applied product
Selection & best practice
Treat WS60 as the flow-control stage of a planned two-part repair, not a one-shot fix. Map the crack, drill and fit mechanical packers at an angle across it at spacing suited to the crack width and concrete section, and flush the crack with clean water first so the resin has moisture to react with and a clear path. Mix only what you can inject within the pot life, and inject from the lowest packer upward, moving to the next port as resin appears. Expect the reaction to be near-instant against flowing water, so keep the pump primed and the sequence tight. Once the leak is arrested and the substrate has dried, re-inject with Fosroc Nitofill UR63 or an epoxy to establish the durable, movement-tolerant seal. Wear gloves and eye protection, work with ventilation, and clean tools and pump with the recommended solvent immediately after use since cured foam is difficult to remove. Store containers sealed in a cool, dry place and use within the shelf life.
Specifications
| Product type | Two-part water-reactive polyurethane injection resin |
| Reaction / cured form | Rigid, water-resistant closed foam |
| Pot life (no water) | 6-8 hrs at 20°C; 3-4 hrs at 35°C |
| Reaction time with water | 5-30 seconds (temperature dependent) |
| Viscosity | 2-3 poise at 20°C |
| Specific gravity | 1.14 ± 0.06 |
| Foam density | Approx. 0.025 |
| Treatable crack width | 0.2 mm to 5 mm (flow dependent) |
| Pack size | 1 litre packs |
| Shelf life | 6 months at 20°C, unopened, dry store |
Industry use cases
Basements & Below-Grade
Arresting live water ingress through raft and wall cracks in commercial and residential basements before a permanent injection seal is applied.
Water & Sewage Infrastructure
Drying out leaking joints and cracks in treatment tanks, sumps and reservoirs so they can be sealed and returned to service.
Tunnels & Metro
Curtain injection behind linings and segmental joints to shut off inflow under hydrostatic pressure during and after construction.
Industrial & Foundations
Sealing lift pits, machine foundations and retaining walls where flowing groundwater must be stopped before structural repair.
Dams & Hydraulic Works
Controlling seepage through cracks in dams, spillways and reservoir walls under a standing head of water.
Frequently asked questions
Is Nitofill WS60 a one-part or two-part product?
Does WS60 give a permanent, final seal on its own?
How quickly does it stop water?
What crack widths can it handle?
Can I apply it by hand or trowel?
Is the cured foam chemically resistant?
How we position Fosroc Nitofill WS60
Nitofill WS60 is the water-stopping first responder in Fosroc’s crack-injection system: use it to kill the flow, then follow with Fosroc Nitofill UR63, a single-component water-reactive PU that cures to a more flexible foam, for the permanent seal on moving or damp cracks. For dry, hairline structural cracks where you want to weld the concrete back together rather than just seal it, move to Fosroc’s low-viscosity epoxy injection resins (Nitofill LV / EPLV family). Where the wider job is tanking a basement or protecting a water-retaining structure, we pair these injection resins with Fosroc’s Nitoproof / Brushbond membrane and Renderoc repair mortar ranges. Across our other brands, comparable water-reactive PU injection systems are available from Sika (SikaFix / Sika Injection PU range) and MC-Bauchemie, which we can specify when a project standard or approval calls for a particular manufacturer. Talk to Space Arc and we will match the resin, packers and pump to your crack condition and water head.
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