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For weatherproofing external concrete, cement render, face brick, and porous pavers where you need to block water ingress without altering the natural appearance of the substrate, Duram S900 is a clear, non-glossy, penetrating siloxane sealer. It sinks deep into the tissue of the material to create a sub-surface water barrier while maintaining vapour diffusion, allowing the treated substrate to breathe and release internal moisture.
How it works
S900 penetrates porous masonry, block work, sandstone, and terracotta to form a hydrophobic barrier below the surface. By blocking liquid water ingress while remaining permeable to water vapour, the treatment helps prevent structural and aesthetic failures. It stops rain and salt spray from driving into the substrate, which minimizes the migration of soluble salts to prevent efflorescence. This dry sub-surface environment also assists in preventing mould and fungus growth, and protects reinforced concrete from steel corrosion caused by water and carbon dioxide permeability. The siloxane chemistry is stable under high pH conditions, making it suitable for application over new concrete and lime-based mortars.
Numbers that matter
- 6m² per litre: Estimated coverage rate when treating grout lines on ceramic tiled areas.
- 4m² per litre per coat: Estimated coverage rate for face brick surfaces to ensure adequate penetration.
- 3m² per litre per coat: Estimated coverage rate for terracotta tiled areas.
- 2m² to 3m² per litre per coat: Minimum coverage floor for highly porous areas to achieve an effective waterproofing barrier.
- 12 to 24 hours: Time required at 25°C and 50% relative humidity to reach full cure and service readiness.
Where to use it
S900 is suitable for external application on porous vertical and horizontal substrates, including:
- Concrete and cement render
- Block work and face bricks
- Porous pavers and terracotta pavers
- Sandstone and other highly porous masonry
Application and preparation
The substrate must be completely sound, stable, clean, dry, and free of existing paints, sealers, efflorescence, or laitance. Efflorescence must be wire-brushed, washed, and allowed to dry fully before application. S900 can be applied by brush, roller, spray, or by pouring. It is essential to wet-soak the surface; apply a soaking coat, allow it to absorb, and immediately apply additional coats wet-on-wet until the substrate is thoroughly saturated.
Limitations
- S900 relies on the soundness and stability of the host substrate; it penetrates the tissue and will not bridge or seal cracks.
- Cracks must be repaired prior to application. If using flexible sealants, apply them after S900 has cured, as the solvent carrier may pit or dissolve the sealant.
- Highly porous, sandy, or friable surfaces may lack the density required to absorb and build up an adequate barrier. Test areas are highly recommended to verify absorption and ensure latent salts do not cause discolouration.
- Sealed surfaces may become slippery when wet.
Frequently asked questions
Does Duram S900 change the appearance or gloss of masonry?
No, Duram S900 dries clear and non-glossy. It forms a sub-surface barrier, preserving the original look of porous mineral substrates while limiting water ingress.
How do I apply S900 on highly porous or friable areas?
Apply multiple wet-on-wet soaking coats until the substrate refuses further absorption. Test a small area first to confirm uptake, then target porous zones with additional passes for adequate penetration.
What is the typical cure time before service?
At 25°C and 50% relative humidity, Duram S900 is touch dry in 2–4 hours and achieves full cure in 12–24 hours. Conditions like substrate porosity, temperature, and ventilation will influence drying.
Can Duram S900 seal cracks in masonry?
No, Duram S900 relies on the integrity of the substrate. It is designed to penetrate and protect porous surfaces, not to bridge or fill existing cracks. Repair cracks before application.
Applications and benefits
| Application | Key benefit | Primary trades |
|---|---|---|
| External concrete, render, face brick, block walls | Sub-surface weatherproofing without altering the original appearance or breathability. | Waterproofers, Builders |
| Sandstone and porous pavers | Limits water uptake and staining through deep penetration into absorbent substrates. | Builders, Remedial Contractors |
| Terracotta and grout lines | Minimises efflorescence at joints by targeted saturation of porous areas. | Tilers, Waterproofers |
Applying Duram S900: Enhanced Protocols & Best Practices
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Surface Preparation
Substrate must be sound, stable, dry and clean. Remove dust, coatings, laitance and efflorescence. Repair cracks as required.
Mechanical Clean
Wire-brush to remove laitance/salts, then wash and allow to dry.
Masking
Mask adjacent non-porous finishes to prevent incidental wetting.
Timing: Proceed only when substrate is dry.Pro Tip: Always complete a small test area to confirm appearance and the number of soaking coats required. -
Saturation Application (Wet-on-Wet)
Apply by brush, roller, spray or pour. Saturate the surface so S900 is absorbed into the pore structure.
First Soaking Coat
Flood the surface to initiate penetration and allow absorption.
Immediate Follow-Up Coats
While still wet, apply additional soaking coats. Repeat several times until refusal to ensure adequate build within the substrate.
Timing: Maintain wet-on-wet. If a coat cures, further coats may be applied after curing.Pro Tip: Focus extra passes on grout lines, edges and visibly porous patches. -
Curing & Return to Service
At 25°C/50% RH: touch dry 2–4 h; set 4–6 h; full cure 12–24 h. Application temperature 5–30°C; service temperature 0–50°C.
Pro Tip: Maintain ventilation to assist solvent evaporation and uniform curing. -
Clean Up
Clean tools and incidental spills with Duram Solvent or Tremco Xylol.
Product limitations
- Not for: Bridging or sealing cracks; Duram S900 relies on the substrate's soundness and porosity for performance.
- Limited efficacy on: Highly porous or friable areas without multiple soaking coats. Always test a small area first to confirm adequate uptake.
- Safety concern: Sealed surfaces can become slippery when wet.
Safety and handling
Duram S900 is flammable, classified as Class 3 dangerous goods.
Personal protective equipment
Wear solvent-resistant gloves, a mask, and eye protection during application and clean-up.
Ventilation
Ensure adequate ventilation during application and curing, especially in enclosed spaces.
First aid
- General: Refer to the product Safety Data Sheet (SDS) for detailed first aid instructions. Seek medical attention for significant exposure.
Storage and disposal
Keep away from ignition sources. Store upright in its original unopened packaging in a cool, dry place. Product has a shelf life of 12 months when stored correctly.
Substrate guide
Proper surface preparation ensures Duram S900 achieves maximum penetration and forms an effective sub-surface barrier.
Concrete, cement render, blockwork, face brick
Surface prep: Ensure surfaces are sound, dry, clean, and free of dust, laitance, efflorescence, coatings, and contaminants. Wire-brush to remove loose material, wash, and allow to dry completely. Repair any cracks before application.
Primer: Not required. Proceed with wet-on-wet saturation coats to achieve adequate pore filling.
Sandstone, porous and terracotta pavers
Surface prep: Remove all friable material and surface salts. Clean surfaces thoroughly and allow them to dry completely. Mask adjacent finishes to prevent unintended contact.
Primer: Not required. Apply multiple wet-on-wet soaking coats until refusal due to high porosity.
Duram S900 Physical Properties
| Property | Value |
|---|---|
| Base Chemistry | Siloxane |
| Appearance | Clear, Non-gloss |
| Colour | Clear |
| pH Compatibility | Suitable for new concrete and lime-based mortars/bricks |
| Skin Time | 2–4 hours at 25°C, 50% RH |
| Initial Cure | 4–6 hours at 25°C, 50% RH |
| Full Cure | 12–24 hours at 25°C, 50% RH |
| Application Temperature | 5°C to 30°C |
| Service Temperature | 0°C to 50°C |
| Water Vapour Transmission | Allows vapour diffusion |
| Coverage Rate | 2–3 m²/L per coat |
| Clean Up | Duram Solvent or Tremco Xylol |
| Classification | Flammable (Class 3 Dangerous Goods) |
| Packaging | 15 L pail |
| Shelf Life | 12 months (unopened, stored correctly) |
| Storage Conditions | Store upright in a cool, dry place in original unopened packaging |
| Application Technique | Wet-on-wet soaking coats until refusal |