Fosroc Nitofill PU 1F
Single-component polyurethane injection resin that foams the instant it meets water, sealing live cracks in basements, tanks and tunnels where epoxy injection cannot go.
What is it?
A one-part, moisture-reactive polyurethane grout that stays liquid in the pail and expands into a tough elastic foam the moment it contacts water inside a crack.
Where is it used?
Actively leaking cracks and construction joints in basements, water tanks, sump pits, manholes, tunnels, retaining walls, canals and other water-retaining or below-ground concrete.
Why use it?
It works wet. Where two-part epoxy needs a dry, dormant crack, Nitofill PU 1F reacts with the very water that is leaking, chasing the flow path and stopping running water in seconds.
How is it applied?
Injected under pressure through packers drilled at 45 degrees across the crack line, using a single-component electric injection pump, working bottom-up on vertical cracks.
About Fosroc Nitofill PU 1F
Nitofill PU 1F is Fosroc’s answer to one of the most frustrating problems on a repair site: a crack that will not stop leaking long enough to be treated. Conventional epoxy injection resins demand a clean, dry, non-moving crack, which is exactly what an active seepage will not give you. This product turns the water into an ally. It is a one-part liquid pre-polymerised polyurethane that reacts on contact with moisture, expanding into a closed, elastic foam that fills the crack and physically blocks the flow path. Because the reaction is driven by the leak itself, the resin travels wherever the water travels, sealing branches and voids that a rigid grout would miss.
For engineers and applicators across Delhi NCR and India, that translates into a practical, single-drum solution for wet-condition sealing with no mixing, no catalyst and no proportioning errors on site. It cures to a permanently flexible seal that tolerates substrate movement in excess of ten percent and withstands wet-dry and thermal cycling, so the repair holds up in the very structures where movement and water go hand in hand, from tank walls and sump pits to tunnel linings and retaining walls. As an authorised Fosroc distributor and applicator, Space Arc Engineering supplies Nitofill PU 1F alongside the packers, surface-sealing paste and hole-filling mortars needed to complete the injection system correctly.
The technical insight
The chemistry is what sets a hydrophilic-style foaming PU apart from epoxy. Nitofill PU 1F is a pre-polymer carrying reactive groups that stay dormant while the drum is sealed. When it enters a wet crack, water triggers polymerisation and releases gas, causing the resin to expand into a foam with a volumetric factor of roughly 350 to 400 percent at a 1:1 water ratio. That expansion does two jobs at once: it drives resin deep into fine fissures a low-viscosity liquid could reach on its own, and it exerts pressure that seats the foam firmly against the crack faces. A gel time near 20 seconds and full foaming by around 180 seconds mean the material sets before the leak can flush it away, which is precisely why injection technique and packer placement matter so much on high-pressure leaks. On dry, non-structural cracks that still move, the same resin can be run as a two-component system by injecting it 1:1 with water, giving a controlled elastic foam without relying on ambient moisture.
Where it is used
- Sealing actively leaking cracks in basement walls, rafts and retaining walls
- Stopping water ingress at construction joints in water-retaining structures
- Waterproofing tunnels, shafts and underground box structures against seepage
- Sealing cracks and joints in tanks, sump pits, manholes and canals
- Emergency control of running-water leaks ahead of permanent lining works
- Injecting fine cracks (down to 0.2 mm) where flow permits penetration
- Two-component 1:1-with-water injection of dry, moving non-structural cracks
- Foam curtain and void filling behind leaking concrete where water is present
Key advantages
- Truly single-component: no mixing, no catalyst, no on-site proportioning errors
- Reacts with water, so it seals live leaks that stop epoxy injection dead
- Low 400 mPa.s viscosity penetrates fine cracks before it foams and expands
- Expands 350-400 percent, chasing the flow path and pressing into the crack faces
- Cures to a permanently elastic seal that tolerates over 10 percent substrate movement
- Withstands wet-dry cycling and thermal movement in water-retaining structures
- Fast 20-second gel and 180-second foam set before the leak can wash it out
- Non-toxic once fully cured; runs on standard single-component injection pumps
Limitations & considerations
- Needs water to cure; dry cracks must be pre-injected with water or run 1:1 with water
- As a flexible foam it seals and waterproofs but does not restore structural crack strength
- Injection quality depends heavily on operator skill, packer spacing and pump control
- Flammable (flash point 107 C): keep away from ignition sources and use ventilation
- Humidity-sensitive in storage; keep the pail sealed until the crack is ready to inject
- Over-pressurising injection can crack the concrete further or blow out the packers
Selection & best practice
Prepare the crack first: clean the surface, remove loose or contaminated material by water-jetting or light abrasive blasting, and flush out dust. Drill packer holes at a 45-degree angle so they bisect the crack near mid-depth, spaced 150 to 500 mm apart depending on crack width, concrete thickness and water pressure; stagger ports on both faces of a through-crack. Where flow allows, surface-seal the crack line between packers with Nitomortar TC2000 (about 30-40 mm wide, 2-3 mm thick); on severe leaks this putty step can be skipped. Inject with a single-component electric pump, starting at the lowest packer on vertical cracks and working upward, feeding methodically point to point without over-pressurising. Open the pail only when you are ready to inject, since a surface skin can form. If there is no active water, pre-inject the crack with clean water. Afterwards remove the packers, fill the holes with Renderoc Plug, scrape off foam residue, and clean tools immediately with Fosroc Solvent 102 before the resin hardens. Given how much the result depends on technique, use an experienced applicator for high-pressure leaks.
Specifications
| Type | Single-component, moisture-reactive foaming polyurethane injection resin |
| Gel time | 20 seconds (at 25 C) |
| Foaming time | 180 seconds (at 25 C) |
| Density | 1.1 kg/L |
| Viscosity | 400 mPa.s |
| Solids content | 100% |
| Expansion (volumetric, 1:1 water) | 350-400% |
| Minimum crack width treatable | 0.2 mm (subject to water flow) |
| Packaging | 20 kg pail (yield approx. 18 L) |
| Shelf life / storage | 12 months unopened; store dry, 5-30 C, away from frost and heat |
Industry use cases
Basements & below-ground
Sealing live seepage through raft and retaining-wall cracks in deep basements and podiums where the water table keeps the crack permanently wet.
Water & wastewater
Stopping leaks in tanks, sump pits, manholes and treatment structures, curing to a flexible foam that survives fill-and-empty cycles.
Tunnels & metro
Curtain and crack injection against hydrostatic ingress in tunnel linings, shafts and cut-and-cover box structures during and after construction.
Infrastructure & hydraulics
Sealing cracks and joints in canals, culverts, dams and retaining walls subject to continuous water pressure and thermal movement.
Repair & rehabilitation
Emergency water control on leaking joints and cracks as a first step before permanent lining, coating or structural repair works proceed.
Frequently asked questions
Can Nitofill PU 1F stop a crack that is actively leaking water?
How is it different from Fosroc Nitofill LV epoxy injection resin?
Do I need to mix it or add a catalyst?
What if the crack is dry when I want to inject?
How small a crack can it seal, and how do I space the packers?
What pack size does it come in and what is the shelf life?
How we position Fosroc Nitofill PU 1F
Nitofill PU 1F is the wet-crack specialist in a complete injection system rather than a standalone product. Pair it with the companion Fosroc materials the job actually needs: Nitomortar TC2000 epoxy paste to surface-seal the crack line between packers, and Renderoc Plug rapid-set mortar to fill the packer holes and handle any gushing pressure leak before injection begins; clean up with Fosroc Solvent 102. When the crack is dry and dormant and the real goal is to restore structural strength rather than stop water, move to Fosroc Nitofill LV, the low-viscosity epoxy injection resin, instead. For broader below-ground protection around these repairs, Space Arc also supplies waterproofing membranes and coatings from Fosroc and our other brands including Dr. Fixit and Sika to complete the envelope.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.