• brush applied airtightness that spans large gaps and used externally on a building
  • Passive Purple External airtight fire rated facade waterproofing membrane 5kg brush applied
  • Passive Purple External airtight fire rated facade waterproofing membrane 5kg brush applied
  • Passive Purple External airtight fire rated facade waterproofing membrane 5kg brush applied
  • Passive Purple External airtight fire rated facade waterproofing membrane 5kg brush applied
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Passive Purple External Airtight Fire Rated Façade Waterproofing Membrane (5kg) - Purple Brush

Passive Purple External Airtight Fire Rated Façade Waterproofing Membrane (5kg) - Purple Brush

£55.99 GBP
£55.99 GBP
excl. VAT
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Passive Purple External Brush, specifically designed to seal joints and gaps with precision and durability. This advanced liquid-applied weather barrier is perfect for external applications where airtightness and weather protection are critical. The brush version contains specialised fibres, allowing it to span larger gaps and joints, delivering exceptional coverage and performance in challenging areas.

Tested & Certified — fire-rated, watertight & breathable

Independently certified to both European (EN) and US (ASTM) standards:

  • 🔥 Reaction to fire Euroclass B-s1,d0 (EN 13501-1, on A1 substrates ≥653 kg/m³) & ASTM E84 Class A (Flame Spread 0 / Smoke 15)
  • 💧 Watertight Class W1 (EN 13859-2) & water permeability Class W3 (EN 1062-3); near-zero water absorption (EN 16302)
  • 🌬️ Breathable / vapour-open — Sd ≈ 0.6 m (EN ISO 12572)
  • 🧱 Crack-bridging A3 (23°C) / A4 (-10°C) (EN 1062-7) & CO₂ / carbonation barrier Class C1 (EN 1062-6)
  • ☀️ UV-stable (strength increases after 500 h UV) · low-emission EMICODE EC2 · anti-fungus (rating 0)
  • 🇬🇧 Kiwa BDA Agrément (BAW-21-214-P-A-UK) · Passive House component (phB) · US ICC-ES AC212 water-resistive barrier

See all test data & certifications → · read about Passive Purple External

Quality assurance: Download the free Installation & QA Record sign-off sheet (IM-QA-05) for this product.

  • Details
  • Uses
  • Technical Data
  • Data Sheets
  • FAQ

Key Features and Benefits:

Seals Joints and Gaps: The brush-applied Passive Purple External is designed to seal even the most challenging joints and gaps, ensuring complete weatherproofing and airtightness. The added fibers provide extra strength to span wider gaps and irregular surfaces, offering a durable and long-lasting seal.

Weatherproof Protection: Formulated for external use, this product provides a robust barrier against wind, rain, and other environmental elements. It ensures that the building envelope remains airtight while keeping moisture out, offering superior protection in all weather conditions.

Enhanced Airtightness: Like all Passive Purple products, this brush version maintains excellent airtightness, making it ideal for projects focused on energy efficiency and Passivhaus certification.

Brush-On Flexibility: The brushable formulation allows for easy application in difficult-to-reach areas and on complex surfaces, ensuring that every joint, crack, and gap is securely sealed. This makes it perfect for both new builds and retrofits.

Ideal for External Use: Designed for external walls, roofs, and other weather-exposed areas, the brush version of Passive Purple External ensures your building stays protected from the elements while maintaining a breathable, airtight seal.

Can Adhere to Any Form of Construction and includes:

– Insulation panels
– Concrete and brick walls
– Fibre cementboards
– Engineered wooden panels / osb panels

Directions of use:

  • Remove salt efflorescence, dust, loose parts and standing water from the surface
  • Apply on a closed surface; if necessary, fill holes and joints with a fast setting cement based product or polyurethane foam
  • Apply Passive Purple External at T < 5°C (also substrate temperature)
  • Application on humid surfaces is allowed, but remove standing water
  • Do NOT add water or solvents
  • Do NOT apply in full sunlight
  • Do NOT apply during rain
  • Clean tools with water after use

Usage:External
Applied By:Brush
Colour:Purple
Certification:BS Fire Class B

Passive Purple External Brush - Technical Data Sheet (TDS)

Passive Purple External Brush - Install Guide

Passive Purple External Brush - Safety Data Sheet (SDS)

Resistance To Mould Growth - Passive Purple External Brush

3D Detail Drawings - Booklet Set One

3D Detail Drawings - Booklet Set Two

3D Detail Drawings - Booklet Set Three

3D Detail Drawings - Timber Frame

Detail Drawings - SIPS (PDF)

All 3D Detail Drawings

At Intelligent Membranes, we help architects, contractors, retrofitters and self-builders achieve airtightness and waterproofing targets with liquid-applied systems. Our flagship airtight system, Passive Purple®, is airtight at all times yet breathable when the building fabric needs to release vapour — we call this intelligent breathability.

Read more...

Why Choose Passive Purple External?

  • Cost Effective – Brush application allows precise coverage of joints and gaps, reducing waste while delivering reliable facade protection.
  • VOC Free – Passive Purple External is water-based and VOC-free. You won’t find any nasties in our airtight paints.
  • Easy Application – Designed specifically for brush application, making it ideal for detailed work, joints, gaps, and hard-to-reach areas.
  • External Use – Applied to the external facade to create a super-tough, watertight vapour control membrane for weatherproofing and UV resistance.
  • Breathable – Allows vapour where needed while ensuring the facade remains airtight.

Shipping & returns summary

We, at Intelligent Membranes, would like you to be 100% satisfied with your purchase and our service. In the unfortunate event of any item being unsuitable or wrong, please read the following for advice on returning goods to us.

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For architects and specifiers

How to specify this product

The NBS clauses and Uniclass codes this product is specified under, with clause wording you can paste straight into your specification.

NBS clauses

  • P10/320Breather membrane
  • H92/785Breather membrane

Uniclass 2015

  • Pr_25_57_10_94Vapour-permeable sheets
View on NBS SourceGet specification support

Clause wording

BREATHER MEMBRANE – DETAILING
Manufacturer: Intelligent Membranes Ltd, Cambridge. Tel 01223 208174. intelligentmembranes.com
Product reference: Passive Purple External Brush, brush-applied airtight, rain-tight, vapour-permeable membrane for joints, junctions, openings and penetrations.
Reaction to fire: Class B to EN 13501-1.
Field area: Passive Purple External / Passive Purple X spray/roller grade over the detailing.
Installation: In accordance with the manufacturer's current technical data sheet and installation guide.

Check against the current technical data sheet before issue. Certificates are in the Downloads tab.

Discover which Intelligent Membranes product best fits your build with our handy comparison table.

Watch Passive Purple External Airtight Fire Rated Façade Waterproofing Membrane (5kg) - Purple Brush in Action