a can of liquid breather membrane that is also a weatherproof membrane
passive purple external waterproof breather membrane that is liquid applied
Timber frame with passive purple external being used as a waterproof airtight liquid breather membrane
Passive Purple external breather membrane that is liquid applied and passivhaus certified
spray applied airtight liquid facade membrane that is airtight and passivhaus certified
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SKU: IM/00PPE10

Passive Purple External Airtight Fire Rated Façade Waterproofing Membrane (10kg) – Spray / Roller

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Usage: External or Internal
Applied By: Roller or Spray
Colour: Purple, Black,Cream or White
Size: 10kg
Certification: BS Fire Class B | ASTM Fire Class A
Sample Available Here

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Our Fire Class B Liquid Applied Weather Barrier is an advanced protective solution designed to meet the highest standards of fire safety and energy efficiency. This versatile weather barrier is Passivhaus certified, ensuring airtightness and thermal performance, while also providing robust protection against external weather conditions.

Key Features and Benefits:

  • Fire Class B Rated: Specifically designed with fire safety in mind, this weather barrier offers a Class B fire rating, providing enhanced resistance to flame spread and adding an extra layer of safety to your building projects.
  • KIWA Approved: Approved as an intelligent moisture management membrane.
  • Passivhaus Certified: This product is meticulously engineered to meet the stringent requirements of Passivhaus standards, ensuring optimal airtightness and energy efficiency. It’s ideal for creating sustainable, eco-friendly, and low-energy buildings.
  • Liquid Applied for Seamless Coverage: Unlike traditional sheet barriers, our liquid applied membrane forms a seamless, continuous layer that conforms to any surface. This eliminates weak spots like seams and overlaps where air or moisture could penetrate.
  • Weatherproof Protection: Designed to withstand harsh environmental conditions, it acts as a powerful barrier against wind, rain, and other external elements, ensuring the building envelope remains airtight and protected.
  • Versatile Application: Suitable for a variety of substrates, including timber, steel, and concrete, this weather barrier can be applied to both new builds and retrofit projects, making it a flexible choice for a wide range of construction needs.

Why Choose This Weather Barrier?

  • Energy Efficiency: Helps reduce energy consumption by minimizing air leakage, contributing to a more sustainable and cost-effective building.
  • Fire Safety: Provides peace of mind with a certified fire safety rating, meeting the latest building regulations.
  • Long-Lasting Durability: Offers long-term protection against weather and fire, ensuring your building remains safe and energy-efficient for years to come.

With its combination of fire safety, KIWA Approved, Passivhaus certification, and superior weatherproofing capabilities, our Fire Class B Liquid Applied Weather Barrier is the smart choice for those looking to build safe, sustainable, and high-performance structures.

Passive Purple External is a waterproof moisture management coating that helps with dampness and vapour. It is at Passivhaus level and is proven to achieve above the required levels of airtightness to meet building regulations. As an added bonus it is fire class B making it the ideal solution for any building project. It offers methane and anti carbonation protection.

It is the new and intelligent method of moisture management and is preferred to traditional paper membranes because of its fast drying and easy installation using spray and roller. It flexes when the building has movement and has no space inbetween the wall making the coverage fully protected. The fire protection increases safety, whereas traditional paper membranes burn like hell in the event of a fire. It is robust and does not tear.

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Tin Coverage
Masonry: 8m2
Timber: 13m2
Plasterboard: 15m2 per tub

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View on BIM Object

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Not just in purple. Browse our product spec for more colours. 

 

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You Will Need

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  • Key Details

    Why Choose Passive Purple External?

    Passive Purple External is the ultimate airtight and weatherproof vapour control paint, engineered for high-performance building envelopes. Whether for retrofit or new build projects, it delivers unbeatable protection, speed of application, and long-term durability.

    ✅ Key Benefits

    • 💰 Cost Effective – A single installer can cover up to 300m² per day using an airless spray device. That means faster application, reduced labour costs, and quicker project delivery.

    • 🌍 VOC-Free & Eco-Friendly – Water-based and completely VOC-free, making it safe for applicators, building occupants, and the environment.

    • 🎨 Flexible Application – Apply with an airless spray machine for large projects or a roller for smaller areas and touch-ups.

    • 🛡 External Protection – Creates a tough, watertight airtight membrane on external facades, providing UV resistance and long-term weatherproofing.

    • 🔥 Fire Rated – Certified Class B fire resistance, outperforming standard membranes and coatings for safety and compliance.

    • 💨 Breathable Airtightness – Intelligent design ensures buildings stay airtight and smoke-tight, while still allowing vapour to escape where needed.

    • 📜 KIWA Approved – Independently tested and certified for performance, giving you confidence on every project.

    👉 With airtightness, fire safety, weather protection, and breathability combined in one product, Passive Purple External is the smart choice for architects, builders, and retrofit specialists who want certified performance without compromise

  • Description

    Excelling Characteristics of Passive Purple External

    Passive Purple External is the world’s first and only Fire Class B liquid-applied airtight paint, offering unmatched performance for both internal and external applications. It combines airtightness, weather protection, and intelligent moisture management in a single certified solution.

    Key Benefits & Features

    • 🔥 Fire Class B – exceptional fire resistance, setting it apart from standard membranes.

    • 🌧 Raintight & Vapour Breathable – keeps water out while allowing moisture to escape, ensuring a healthy building fabric.

    • 🔒 Airtight & Smoke-Tight – delivers a complete barrier to uncontrolled air leakage and smoke movement.

    • ☀️ UV Resistant & Self-Cleaning – long-term durability with reduced dirt pickup and surface staining.

    • 🦠 Anti-Fungus Protection – prevents mould growth and safeguards indoor air quality.

    • 🧱 Crack-Bridging – maintains airtightness even where movement or minor cracks occur.

    • 🧪 Concrete Protection – blocks carbonation, provides realkalisation, and shields against salts from roads and de-icing.

    • 🌍 Dual Purpose – suitable for internal and external applications across retrofit and new build projects.

    • 💨 Intelligent Moisture Management – allows the substrate to breathe, balancing vapour openness with airtight performance.

    👉 With Passive Purple External, you get airtightness, weather resistance, and long-term structural protection in one advanced, certified liquid membrane — perfect for timber frame, retrofit, and high-performance construction projects

    Additional information

    Choose Option

    75mm x 25m (Single Roll), 75mm x 25m (Box of 5), 100mm x 25m (Single Roll), 100mm x 25m (Box of 4), 150mm x 25m (Single Roll), 150mm x 25m (Box of 2), 200mm x 25m (Single Roll), 200mm x 25m (Box of 2)
  • Uses

    Substrates & Compatibility

    Passive Purple External is designed for maximum versatility and can adhere to virtually any form of construction, including:

    • 🧱 Concrete and brick walls

    • 🪵 Engineered timber panels / OSB panels

    • 🧩 Insulation boards and panels

    • 🪨 Fibre cement boards

    This makes it the ideal solution for both new build and retrofit projects, across residential, commercial, and industrial applications.

    Directions for Use

    For best results, follow these application guidelines:

    ✅ Surface Preparation

    • Remove salt efflorescence, dust, loose materials, and standing water.

    • Apply only on a closed surface – fill holes and joints first with a fast-setting cement-based product or polyurethane foam.

    ✅ Application Conditions

    • Substrate temperature: above 5°C.

    • Application on humid surfaces is permitted, but standing water must be removed.

    • Do not add water or solvents.

    • Do not apply in direct full sunlight or during rain.

    ✅ Application Method

    • Apply using an airless spray device (e.g., Graco) or with a paint roller.

    • Always apply two coats. Allow the first layer to dry fully before applying the second.

    • Clean all tools immediately with water after use.

  • Data Sheets & Certificates
    Technical Data Sheet (TDS)
    Safety Data Sheet
    Install Guide
    Kiwa Agrement
    Safety Data Sheet (SDS)
    3D Images
    Passivhaus Institut Certificate 2025
  • Architects Specification

  • Reviews

    Reviews

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  • Delivery

    All delivery charges are included in the price of the products and are dependent on the products selected for purchase. This charge is based on delivery to mainland UK, excluding the Scottish Highlands & the Islands where additional shipping charges will apply. For more information read our delivery policy in full.

    Intelligent Membranes do not offer a next day delivery service.

    Intelligent Membranes aim for deliveries to be with the customer within 2 working days. During the festive period deliveries could take longer.

    Orders placed before 12pm will be dispatched the same day, any orders placed after 12pm will be dispatched the following working day

  • Returns

    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 our returns policy in full.

Passive Purple External – FAQ

1. What is Passive Purple External?

Passive Purple External is the world’s first and only Fire Class B airtight paint, designed for both internal and external applications. It is a liquid-applied, spray- or roller-applied membrane that creates a seamless, airtight and vapour-open barrier.

2. What makes it different from standard airtight paints?

  • Fire Class B rated (EN 13501-1).

  • It can be applied both internally and externally.

  • Vapour-open and breathable (prevents trapped moisture).

  • Smoke-tight and airtight.

  • Fully certified by the Passivhaus Institute.

  • The only product in its category with this unique combination of properties.

3. Where can Passive Purple External be used?

  • External weather barrier for timber frame constructions.

  • Internal air barrier for retrofit and new build projects.

  • Sealing complex junctions, penetrations, and connections.

  • Suitable for walls, roofs, soffits, and façades.

4. Is Passive Purple External suitable for retrofit projects?

Yes. Its breathability (vapour-open) ensures existing walls can “breathe,” while creating airtightness for energy efficiency and comfort. Perfect for upgrading existing housing stock without trapping moisture.

5. How is it applied?

  • By airless spray for larger areas.

  • By roller or brush for detail work.

  • No joints, overlaps, or tapes needed—seamless finish.

6. How thick does it need to be applied?

A wet film thickness of 0.8–1.0 mm is required to achieve the correct dry film performance. A wet film gauge should be used during application.

7. How is airtightness tested?

Passive Purple External can achieve <0.6 ACH@50Pa (Passivhaus standard) when applied correctly. Airtightness is verified via blower door testing.

8. What substrates can it be applied to?

  • Timber

  • OSB/Plywood

  • Masonry

  • Concrete

  • Plasterboard

  • Other mineral-based surfaces (with a suitable primer if dusty/porous)

9. Do I need a primer?

On very porous or dusty substrates, a primer such as IM Primer or Lime Prime is recommended to ensure maximum adhesion.

10. Is it weather-resistant?

Yes. Once cured, Passive Purple External acts as a temporary weather barrier. It resists rain and UV during the construction phase, protecting the building fabric until cladding or external finishes are installed.

11. What’s the fire classification?

It is Fire Class B (EN 13501-1) — significantly safer than standard airtight paints that are typically Class E.

12. Is it breathable?

Yes. It is vapour-open (breathable) while still airtight and smoke-tight, allowing trapped moisture to escape.

13. Can it be repaired if damaged?

Yes. Any penetrations or damage can be resealed quickly with brush- or roller-applied Passive Purple External.

14. What certifications does it carry?

Passive Purple External is one of the most tested and certified airtight paints in the world. It holds:

    • Passivhaus Institute Certification – verified airtight component.

    • EN 13501-1 Fire Class B classification.

    • KIWA BDA Agrément – independent third-party approval for construction use.

    • ICC-ES (International Code Council Evaluation Service) – approval for the North American market.

    • Tested for airtightness, vapour diffusion, weather resistance, and smoke-tightness.

15. How long does it last?

Once applied and protected by external finishes (cladding, render, brick, etc.), Passive Purple External provides a permanent airtight layer for the lifetime of the building.

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