Repair Systems — 03 — Facade & External Envelope
Sika Protectosil penetrating silane-siloxane water repellent
Technical product reference for Sika Protectosil BHN and CIT penetrating silane water repellents by Sika Australia. Covalently bonds within the pore structure of masonry and concrete — no surface film — colourless — vapour permeable. Reduces water absorption up to 95%. Applied by flood coat at 150–250 mL/m². Masonry must be clean, dry, and all defects repaired before treatment.
What is Sika Protectosil penetrating silane water repellent?
Sika Protectosil BHN and CIT are penetrating silane water repellents that chemically bond within the pore structure of masonry and concrete, forming a hydrophobic lining without a surface film. Applied by flood coat at 150–250 mL/m², the treatment reduces water absorption by up to 95% while maintaining vapour permeability. The treated surface is colourless and unchanged in appearance. Masonry must be clean and dry. All cracks and defects must be repaired before application.
Supplier reference — Sika Protectosil penetrating silane
Sika Protectosil BHN / CIT penetrating silane water repellent
Deep-penetrating silane water repellent — covalently bonds within pore structure — reduces water absorption up to 95% — no surface film — vapour permeable — for porous masonry, brick, stone and render
Sika Protectosil — key technical data
| Attribute | Value |
|---|---|
| Supplier | Sika Australia |
| Product range | Protectosil BHN / CIT |
| Type | Penetrating silane |
| Surface film | None (penetrating treatment) |
| Vapour permeable | Yes |
| Penetration depth | 10–30 mm depending on substrate |
| Water absorption reduction | Up to 95% |
| Coverage rate | 150–250 mL/m² (flood coat) |
| Application method | Brush, roller or low-pressure spray — flood coat |
| Substrate moisture limit | Below 4–6% by weight |
| Reapplication interval | 10–15 years |
| Colourless | Yes — appearance unchanged |
- Water repellent treatment to porous masonry facades after structural repairs, repointing and crack repair are complete
- Supplementary protection on exposed masonry parapets, piers and wind-driven rain faces
- Penetrating treatment of concrete masonry facades to reduce chloride ingress in coastal locations
- Specify Protectosil BHN for general mixed masonry facades — broad-spectrum silane/siloxane blend
- Specify Protectosil CIT for very porous old brick or concrete where maximum penetration depth is required
- Apply as a flood coat — surface must be saturated; inadequate application rate is the most common cause of poor performance
- Does not seal cracks — any crack wider than ~0.1 mm will allow water entry regardless of silane treatment
- Will not stop rising damp or below-ground moisture — silane is a facade water repellent only
- Ineffective on painted, coated, or contaminated surfaces — must penetrate bare masonry pore structure
- AS 3700 — Masonry Structures — references water repellent treatment as supplementary protection
- BS EN 13580 — Products and systems for protection and repair of concrete — water absorption after impregnation
- CCAA Data Sheet — Water Repellent Treatments for Concrete — guidance on silane selection and application
- Porous or absorbent masonry facade where water ingress occurs through the pore structure (not through cracks or open joints)
- Wind-driven rain penetration on exposed elevations where masonry porosity is confirmed as the ingress mechanism
- Efflorescence caused by water cycling through porous masonry — treat after eliminating salts and completing repointing
- Modern fired clay brick — bare, dry, unpainted surface required — flood coat application to saturation
- Historic and heritage brick — confirm Protectosil CIT for very porous old brick — consult heritage specialist
- Concrete masonry block — bare, dry concrete — Protectosil CIT recommended for corrosion protection
Do not confuse Sika Protectosil with:
- Surface-film sealers and coatings — film-forming silicone or acrylic sealers that coat the surface rather than penetrating the pore structure; these can trap moisture, peel, and alter surface appearance; Protectosil is a penetrating treatment with no surface film
- Silicone emulsions — shorter service life (typically 5–7 years vs 10–15 years for silane/siloxane blends); lower penetration depth; confirm the product chemistry before specifying on critical masonry facades
- Anti-carbonation coatings — surface-film barrier coatings applied to concrete to resist CO2 diffusion and slow carbonation; different purpose from water repellent treatment; both may be used in combination on concrete facades
- Elastomeric crack-bridging coatings — these seal cracks through film formation; Protectosil does not bridge cracks and must not be relied upon to seal open defects
- Mapei Antipluviol S — a water-based silane/siloxane blend by Mapei; similar performance; suitable where solvent odour is a constraint during occupied-building applications
Disclaimer
This page provides general technical information only. Silane product selection, application rate, coverage, and re-application interval must be confirmed against the project's masonry type, porosity and exposure conditions. Treatment is supplementary to structural repair — not a substitute for defective masonry remediation. Confirm current product data with the Sika TDS before specifying or applying.