Fosroc Nitocote SN522
A colourless, breathable silicone/silane-siloxane water-repellent impregnation that keeps rain and chloride-bearing salts out of brickwork, concrete, render and stone while letting the surface breathe.
What is it?
A single-component, ready-to-use colourless silicone resin / silane-siloxane water repellent that penetrates porous masonry and reacts to form a breathable, water-repellent lining within the surface pores.
Where is it used?
Exterior facades, fair-faced brickwork, concrete, cement render and natural or cast stone on buildings, bridges, water-retaining and marine-zone structures across Delhi NCR and Pan-India.
Why use it?
It dramatically cuts absorption of rainwater and water-borne chloride salts, reduces efflorescence, freeze-thaw damage and atmospheric staining, yet allows trapped water vapour to escape so the substrate stays dry and self-cleaning.
How is it applied?
Brushed or sprayed directly from the container in two coats onto a clean, dry (or slightly damp) surface, well saturated; covers roughly 4.5-9 m2 per litre depending on porosity.
About Fosroc Nitocote SN522
Fosroc Nitocote SN522 is a colourless, ready-to-use silicone water repellent used to protect exterior masonry from the single biggest cause of facade deterioration in the Indian climate: water ingress. Supplied as a low-viscosity silicone resin solution (the current Fosroc range positions the chemistry as a penetrating silane-siloxane impregnation), it soaks into porous substrates such as brickwork, in-situ and precast concrete, cement rendering and natural or cast stone, then cures within the pores to line them with a hydrophobic, water-repellent layer rather than forming a film on top of the surface.
The distinction matters. Unlike a surface coating or paint, SN522 does not bridge the pores or seal the wall. It works at the capillary level, so the treated surface continues to breathe: water vapour and construction moisture can still escape, but liquid water, water-borne chloride and sulphate salts, deicing salts, soot and atmospheric dirt are largely repelled. The result is a wall that stays drier, resists efflorescence and frost damage, suffers less crazing and cracking, and stays cleaner because pollutants cannot key into a wetted surface.
For Space Arc Engineering’s clients – architects specifying fair-faced brick and exposed concrete, structural consultants worried about chloride-driven reinforcement corrosion, facade and waterproofing contractors, and procurement teams sourcing for residential towers, commercial blocks, heritage restoration and infrastructure – SN522 is a low-cost, high-leverage protective treatment. It is colourless and non-staining, so it preserves the natural colour and texture of architectural masonry, and it is applied straight from the container with no mixing, which keeps application fast and predictable on large facade areas.
A water-based companion product, Nitocote SN522 WB, offers the same penetrating silane-siloxane technology in a low-VOC, water-borne carrier for projects with tighter health, safety or environmental requirements.
The technical insight
Nitocote SN522 is a silicone/silane-siloxane water-repellent impregnation, not a barrier coating – a difference that governs where it succeeds and where it fails. The active silicone resin reacts with moisture and the siliceous or calcareous substrate to chemically bond hydrophobic groups onto the pore walls. This lowers the surface energy inside the capillaries so that liquid water beads and is repelled, while the pores themselves remain open to vapour diffusion. Because the protection lives inside the surface, it is invisible and does not alter appearance or sheen.
Critically, SN522 only resists water under no hydrostatic pressure – it stops wind-driven rain and capillary absorption, but it is not a tanking system and will not hold back water under head. It is therefore a complement to, not a substitute for, membrane waterproofing on roofs, basements and water-retaining structures. The product carries BS 6744-92 Class A compliance on predominantly siliceous substrates (brick, concrete, render, siliceous stone) and Class B on predominantly calcareous substrates (sandstone, limestone, calcium-silicate brick, calcareous stone), so the specifier can match the class to the masonry type. With a 38C flash point the solvent-borne grade is flammable and requires ventilation and no naked flames during application; the WB grade avoids this where solvent handling is a concern.
Where it is used
- Water repellent treatment of fair-faced and exposed brickwork on building facades
- Protection of in-situ and precast concrete elements against rain and chloride ingress
- Sealing of cement-rendered and plastered external walls to reduce dampness and staining
- Treatment of natural and cast stone, including sandstone and limestone facades and heritage masonry
- Reducing efflorescence and salt leaching on new and existing brickwork
- Pre-treatment of porous masonry in coastal and salt-laden atmospheres to limit chloride-driven corrosion
- Improving freeze-thaw durability of exposed concrete and masonry in cold-climate regions
- Self-cleaning surface treatment to reduce soot and atmospheric dirt pick-up in polluted urban environments
Key advantages
- Ready to use – brush or spray applied directly from the container with no mixing
- Colourless and non-staining, preserving the natural colour and texture of brick, concrete and stone
- Breathable – allows water vapour to escape so the substrate is not sealed in damp
- Significantly reduces absorption of rainwater and water-borne chloride and sulphate salts
- Reduces efflorescence caused by soluble salts in brickwork
- Improves freeze-thaw resistance and reduces crazing and cracking in concrete
- Self-cleaning effect – resists soot, dust and atmospheric dirt, reducing facade staining
- Effective on both new and old surfaces
- Complies with BS 6744-92 Class A and Class B depending on substrate
- Decorative coatings can be applied to surfaces previously treated, within material compatibility limits
Limitations & considerations
- Resists water only where there is no hydrostatic pressure – not a tanking or below-grade waterproofing system
- An impregnation, not a film – it does not bridge cracks, fill voids or repair defective masonry or joints
- Surface must be sound, clean and essentially dry; cracks and open joints must be repaired before treatment
- Solvent-borne grade is flammable (flash point 38C) and requires good ventilation, no naked flames and no smoking during application
- Short shelf life of about 6 months; high temperature and humidity storage shortens it further
- Water-based cement or emulsion paints should not be applied over treated areas (apply such paints before SN522)
- Effectiveness and coverage vary with substrate porosity, requiring trial areas for unfamiliar masonry
- Not a decorative finish – it provides no colour, gloss or UV-protective topcoat by itself
Selection & best practice
Always start with a clean, sound and predominantly dry substrate – slight dampness is acceptable but oil, grease, loose particles, decayed matter, moss and algae must be removed (Fosroc Reebaklens is recommended for cleaning). Rake out and re-point unsound brickwork joints with cement-sand mortar gauged with Conplast X421IC before treatment, because SN522 will not bridge gaps. Apply two flood coats evenly by brush or low-pressure spray, working wet-on-wet so porous surfaces are well saturated and no run-off or holidays remain. Match the BS 6744 class to the masonry (Class A for siliceous, Class B for calcareous substrates) and carry out a trial patch to confirm coverage within the 4.5-9 m2/litre band and to check there is no colour change. Ensure ventilation, keep ignition sources away from the solvent-borne grade, mask glazing and metalwork, and apply any decorative emulsion or cement paint before SN522, not after. Clean brushes and equipment with Nitoflor Sol immediately after use, and reseal containers to prevent evaporation. Where low-VOC or solvent-free working is required, specify Nitocote SN522 WB.
Specifications
| Product type | Single-component colourless silicone / silane-siloxane water-repellent impregnation |
| Form | Ready-to-use silicone resin solution (no mixing) |
| Colour / appearance | Colourless |
| Coverage | 4.5-9 m2 per litre on brickwork and smooth cement render, depending on substrate porosity |
| Number of coats | Two coats; porous surfaces well saturated |
| Application method | Brush or spray, applied direct from container |
| Standards compliance | BS 6744-92 Class A (siliceous substrates) and Class B (calcareous substrates) |
| Substrates | Brickwork, in-situ and precast concrete, cement rendering, natural and cast stone |
| Water resistance | Repels rainwater / inhibits surface water ingress where there is no hydrostatic pressure |
| Water-vapour permeability | Breathable – allows surface to release water vapour |
| Flash point | 38 C (solvent-borne grade – flammable) |
| Pack sizes | 1 litre, 5 litre and 20 litre containers |
| Shelf life | 6 months in original packing in dry store; reduced by heat/humidity |
| Equipment cleaning | Nitoflor Sol immediately after use |
| Water-based variant | Nitocote SN522 WB (low-VOC penetrating silane-siloxane) |
Industry use cases
High-rise residential & commercial facades
Two-coat treatment of exposed brick and concrete elevations to cut rain penetration, dampness and staining, extending repaint cycles and keeping facades looking clean in polluted city environments.
Coastal & marine-zone structures
Pre-treatment of porous concrete and masonry in salt-laden atmospheres to reduce chloride absorption and slow chloride-driven reinforcement corrosion, used alongside Fosroc anti-carbonation coatings.
Heritage & stone restoration
Colourless, breathable protection of sandstone, limestone and historic brickwork (BS 6744 Class B) that repels water and reduces efflorescence without altering the appearance of the original masonry.
Infrastructure & bridges
Water-repellent impregnation of exposed concrete piers, parapets and decks to improve freeze-thaw durability and limit ingress of deicing salts and water-borne contaminants.
Institutional & industrial buildings
Treatment of large rendered and fair-faced masonry areas on schools, hospitals and factories to control rising-damp staining and efflorescence, applied rapidly by spray with no on-site mixing.
Frequently asked questions
Is Fosroc Nitocote SN522 a waterproofing membrane?
What surfaces can SN522 be applied to?
How much area does one litre cover?
How many coats are needed and how is it applied?
Will it change the colour or appearance of my facade?
Can I paint over a surface treated with SN522?
How we position Fosroc Nitocote SN522
Within the Fosroc range, Nitocote SN522 is the colourless, breathable water-repellent impregnation for porous masonry, and it pairs naturally with companion Fosroc products that Space Arc supplies: Reebaklens for surface cleaning, Conplast X421IC for re-pointing mortar, and Nitoflor Sol for equipment cleaning. Where a low-VOC or solvent-free option is needed, Nitocote SN522 WB delivers the same penetrating silane-siloxane chemistry in a water-borne carrier. SN522 is best understood as the first line of defence against water ingress – for active anti-carbonation or anti-chloride film protection of concrete, specifiers typically step up to Fosroc Dekguard elastomeric and protective coatings, and for membrane waterproofing to the Fosroc Brushbond or Proofex ranges. Among comparable products on the Indian market, credible silane-siloxane and silicone water repellents include Sika Sikagard-703 W, MBCC/Master Builders Solutions MasterProtect H series, Dr. Fixit Roofseal/silicone water repellents and STP (Pidilite group) impregnation products. SN522’s positioning rests on Fosroc’s established distributor and applicator network, BS 6744 Class A and Class B compliance, simple ready-to-use application and strong availability through authorised channels such as Space Arc Engineering across Delhi NCR and Pan-India; for projects that demand a coloured anti-carbonation finish or guaranteed waterproofing under pressure, a film-forming coating or membrane should be specified instead.
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