Fosroc Nitoproof 21
Solvent-free, cold-applied bituminous emulsion for damp-proofing and vapour-barrier protection on concrete, masonry and foundations.
What is it?
A single-component, water-based bituminous emulsion (type ED to UNE 104231) that dries to a flexible black film acting as a moisture and vapour barrier on building substrates.
Where is it used?
Below-grade and at-grade damp-proofing of foundations, retaining walls, plinth beams, basement and party walls, and as a tanking or vapour-barrier coat behind cladding and screeds.
Why use it?
It is solvent-free, brush- or spray-applied cold without heating or torching, bonds to most common substrates, and gives an economical seamless damp barrier with no joints or laps.
How is it applied?
Applied cold by brush, roller or spray over a clean, sound surface in two coats at roughly 0.5-0.7 kg/m2 total, the first coat allowed to dry before the second is applied at right angles.
About Fosroc Nitoproof 21
Fosroc Nitoproof 21 is a ready-to-use, single-component bituminous waterproofing emulsion supplied as a viscous black liquid that cures by water evaporation to form a continuous, flexible damp-proof film. It is classified as a type ED emulsion under the Spanish standard UNE 104231, which covers non-ionic, paste-consistency bituminous emulsions intended for damp protection of walls, foundations and below-render applications. Because it is water-carried rather than solvent-carried, the product is low-odour, contains no flammable solvents, and can be applied in confined and occupied spaces with far fewer handling restrictions than a hot-bitumen or solvented coating.\n\nThe material is engineered for the unglamorous but critical job of stopping rising and lateral damp. Once cured it works as both a moisture barrier and a vapour barrier, meaning it resists liquid water ingress and slows water-vapour transmission through the structure. Fosroc states good adhesion to the substrates most commonly met on an Indian jobsite – concrete, brick, steel, cork and timber – so a single product can be carried across foundations, blockwork and mixed-substrate junctions without changing systems. It is cold-applied entirely by hand tools or spray, with no torch, no kettle and no primer mixing, which makes it well suited to plinth-level and basement work where naked flames are undesirable.\n\nNitoproof 21 sits at the economical, general-purpose end of the Fosroc Nitoproof waterproofing range. It is not a high-build elastomeric membrane for trafficked roofs or ponded podiums; rather, it is the workhorse damp-proof and vapour-barrier coating that protects buried and concealed surfaces and primes substrates ahead of heavier membrane systems. For Indian contractors and consultants it offers a familiar, brand-backed alternative to commodity bitumen primers and cut-back coatings, with the assurance of a Fosroc technical specification behind it.
The technical insight
The defining technical characteristic of Nitoproof 21 is that it is a type ED bituminous emulsion rather than a cut-back (solvent-thinned) bitumen. In an emulsion, bitumen droplets are dispersed in water; the film forms as the water evaporates and the droplets coalesce. This delivers three practical consequences. First, there is no flammable solvent and very low odour, so it can be used in basements, lift pits and enclosed shafts where solvented primers would be a fire and ventilation hazard. Second, because film formation depends on water evaporation, application is sensitive to ambient conditions – it needs a dry, above-dew-point substrate and must not be applied when rain is imminent, since uncured emulsion can re-emulsify and wash off. Third, the cured film is flexible and continuous, with no joints, laps or seams, so performance does not depend on overlap workmanship the way a sheet membrane does. The published consumption of roughly 0.5-0.7 kg/m2 applied in two coats reflects a thin-film damp-proof and vapour-barrier function, not a high-build trafficable membrane; coverage will move toward the higher figure on porous brick and blockwork and toward the lower figure on dense, smooth concrete. The first coat can be water-diluted to act as a penetrating primer that wets the substrate and improves adhesion, with the second, neat coat building the barrier film.
Where it is used
- Damp-proofing of foundations, footings, plinth beams and grade beams before backfilling
- Tanking and damp protection of basement walls, retaining walls and party walls
- Vapour-barrier coating behind external cladding, dry-lining and rendered finishes
- Damp-proof coating to the underside and edges of ground-bearing floor slabs ahead of screeds
- Protective coating to buried concrete and masonry against soil moisture and ground damp
- Primer / first damp-proof coat on porous masonry ahead of heavier bituminous or membrane systems
- Moisture protection of cork, fibreboard and timber elements in contact with masonry
Key advantages
- Solvent-free and low-odour – safe to use in basements, pits and enclosed, occupied spaces
- Cold-applied by brush, roller or spray with no heating, torching or kettle work
- Seamless, jointless film eliminates the lap and overlap failures common to sheet membranes
- Good adhesion across mixed substrates – concrete, brick, steel, cork and timber
- Acts as both a liquid-moisture barrier and a water-vapour barrier in one coat system
- Economical general-purpose damp-proofing backed by the Fosroc technical specification
- Flexible cured film tolerates minor substrate movement and surface irregularities
- Single-component and ready to use – no mixing of two-part components on site
Limitations & considerations
- Not a trafficable or exposed-roof membrane – intended for concealed, buried and protected surfaces
- Black bituminous film is unsightly and not a decorative or UV-stable finish; protect or overcoat where exposed
- Water-based cure means it must not be applied to damp surfaces, in the rain, or when rain is imminent
- Lower film build than high-performance elastomeric or reinforced systems – limited crack-bridging
- Bituminous coatings can soften at sustained high temperatures and should not be over-coated with incompatible solvented products without checking compatibility
- Requires a dry, clean, sound and laitance-free substrate; performance depends on correct surface preparation
- Always confirm coverage, pack sizes and exact properties against the current Fosroc India datasheet, as regional product data can differ from the international listing
Selection & best practice
Prepare the substrate first: it must be sound, clean and free of laitance, dust, oil, curing-compound residue and loose material, and surface-dry before coating. Make good honeycombing, blowholes and cracks and form smooth fillets at all wall-to-floor junctions so the film is not bridged over a sharp internal angle. Apply the first coat well worked into the surface – diluting it with clean water where a penetrating primer effect is wanted – and allow it to dry before applying the second coat at right angles to the first to even out pinholes and thin spots, targeting roughly 0.5-0.7 kg/m2 in total. Do not apply to wet substrates, when surface temperature is near the dew point, or when rain is expected before the film has cured, as uncured emulsion can wash away. Where the coating will be backfilled, protect the cured film with a protection board or geotextile before placing fill, and allow full cure before covering. Verify the current Fosroc India technical datasheet for drying times, dilution rates and pack data before specifying.
Specifications
| Product type | Single-component bituminous waterproofing emulsion (water-based) |
| Classification | Type ED emulsion to UNE 104231 |
| Function | Moisture barrier and water-vapour barrier (damp-proofing) |
| Solvent content | Solvent-free |
| Appearance (wet / cured) | Black liquid emulsion drying to a black flexible film |
| Coverage | Approx. 0.5-0.7 kg/m2 applied in 2 coats |
| Number of coats | 2 (first coat may be water-diluted as a primer) |
| Application method | Cold-applied by brush, roller or spray |
| Suitable substrates | Concrete, brick, steel, cork and timber |
| Cure mechanism | Air drying by evaporation of water |
| Pack size | Confirm against current Fosroc India datasheet (not stated on international listing) |
Industry use cases
Residential & Commercial Buildings
Damp-proofing of foundations, plinth beams and basement / retaining walls to stop rising and lateral ground damp before backfilling and finishing.
Infrastructure & Civil Works
Moisture and vapour-barrier protection of buried concrete and masonry in culverts, service trenches, pits and below-grade structures across Pan-India projects.
Industrial & Warehousing
Vapour-barrier coating beneath ground-bearing slabs and screeds and to plinths to limit moisture migration into floors and stored goods.
Facade & Envelope
Concealed damp and vapour protection behind external cladding, dry-lining and rendered masonry to keep wall build-ups dry.
Repair & Refurbishment
Re-establishing a damp-proof coating on existing foundations, party walls and below-grade masonry during refurbishment of older NCR building stock.
Frequently asked questions
Is Fosroc Nitoproof 21 a solvent-based or water-based product?
What is the coverage of Nitoproof 21?
Can Nitoproof 21 be used as a primer?
Which surfaces can it be applied to?
Is Nitoproof 21 suitable for exposed roofs and trafficked areas?
How many coats are needed and how should they be applied?
How we position Fosroc Nitoproof 21
Within the Fosroc waterproofing portfolio, Nitoproof 21 is the economical, general-purpose damp-proof and vapour-barrier emulsion – the layer that protects buried foundations, plinths and concealed masonry rather than a finished, trafficked surface. It complements rather than competes with Fosroc’s higher-build systems: where a project needs an exposed or trafficable membrane, the Nitoproof liquid-applied range (for example Nitoproof 600 and the PU-based grades) or a Nitocote elastomeric coating is the right step up, while Nitoproof 21 can serve as the damp-proof base or primer beneath them. For positive-side structural waterproofing of basements and water tanks, crystalline and cementitious options elsewhere in the Fosroc range (such as the Renderoc and cementitious tanking products) address pressurised water that a thin bituminous emulsion is not designed for. Against the wider Indian market, Nitoproof 21 occupies the same niche as bituminous damp-proofing emulsions from Dr. Fixit (such as their bitumen-based damp-proof coatings), STP’s bituminous primers and emulsions, MBS waterproofing emulsions, and the bituminous primers and coatings in the Sika range – so the practical choice often comes down to specification fit, technical support and supply continuity rather than chemistry alone. As an authorised Fosroc distributor and applicator covering Delhi NCR and Pan-India, Space Arc Engineering positions Nitoproof 21 as the dependable, brand-backed damp-proofing choice where a clean, solvent-free, cold-applied bituminous barrier is required, with sister Nitoproof and Nitocote products available where a higher-performance membrane is specified.
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