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Class A W1 Breather Membrane

The Class A W1 Breather Membrane is a product of the ARBOSHIELD Pro® category. It is a high-performance vapour-permeable wall membrane with a low emissivity reflective surface and Class A2-s1,d0 reaction to fire – suitable for all light steel frame and SFS type walling applications.

ARBOShield Pro Class A W1 Breather Membrane open roll
ARBOShield Pro Class A W1 Breather Membrane open roll

Class A W1 Breather Membrane – Fire-Rated Wall Membrane

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Unique properties of Class A W1 Breather Membrane

Resists the spread of fire across the cavity of the façade and can be installed onto almost any substrate.

  • Class A2-s1,d0 reaction to fire

  • Class W1 resistance to water penetration

  • 5,000 hours tested resistance to UV exposure (equivalent to 9 months continuous)*

  • Suitable for modular off-site construction

  • Compatible with almost any substrate – sheathing boards, window frames, concrete, steel and blockwork

  • Airtightness: 0.093 m³/(h × m² at 50 Pa)

Technical Specifications & Downloads

Description/StandardPerformance
Reaction to Fire (EN 13501)A2-s1,d0
Resistance to Water Penetration (EN 13859-1)Class W1
Tensile Strength MD (EN 13859-1) 3200 N/50mm BS EN 12311-1
Tensile Strength CD (EN 13859-1)3000 N/50mm BS EN 12311-1
Flexibility at Low Temperature (EN 13859-1)-40 °C
Water Vapour Transmission (ISO 12572)0.08sd
Resistance to Nail Tearing MD (EN 13859-1)580N BS EN 12310-1
Resistance to Nail Tearing CD (EN 13859-1)450N BS EN 12310-1
UV Resistance5,000 hours passed (9 months
continuous)
Airtightness (EN 12114)0.093 m³/(h × m² at 50 Pa)

Associated Products

Class A Air & Vapour Control Layer - ARBOSHIELD Pro®

ARBOSHIELD Pro® Class A Air & Vapour Control Layer is a high performance air and vapour control layer featuring a low-emissivity reflective surface designed to combine Class A2-s1,d0 fire classification with high tensile strength, enhanced thermal performance and air tightness.

Class B W1 Breather Membrane - ARBOSHIELD Pro®

ARBOSHIELD Pro® Class B W1 Breather Membrane is an extremely vapour permeable wall membrane with Class B-s1,d0 fire classification.

External Perimeter Class A Membrane (EPAM)® - ARBOSHIELD Pro®

The new and unique ARBOSHIELD Pro® External Perimeter Class A Membrane (EPAM)® combines an industry leading self-adhesive, Class A2-s1,d0 fire protection along with a complete waterproofing and airtightness window and façade seal all in one product.

Class A High Tack Sealing Tape - ARBOSHIELD Pro®

ARBOSHIELD Pro® Class A High Tack Sealing Tape has been specifically designed to provide a strong and resilient seal when secured against a membrane lap or detailing such as window and/or door openings.

Frequently Asked Questions

1

Why choose the ARBOSHIELD Pro® Class A W1 Breather Membrane?
The ARBOSHIELD Pro® Class A W1 Breather Membrane is the only breather membrane to combine Class A2-s1,d0 fire classification with Class W1 water resistance and 5,000 hours UV resistance. Its unique composition resists the spread of fire across the façade cavity, making it the correct choice for schools, hospitals, care homes and high-rise residential blocks.

2

What are the key benefits of the ARBOSHIELD Pro® Class A W1 Breather Membrane?
Key benefits include: Class A2-s1,d0 reaction to fire; Class W1 water resistance; airtightness of 0.093 m³/(h × m² at 50 Pa); compatibility with almost any substrate; suitability for modular off-site construction; and the ability to repair minor damage with ARBOSHIELD Pro® High-Tack Sealing Tape.

3

What is the ARBOSHIELD Pro® Fire-Resistant Façade System?
It is a complete, innovative solution for façade and apertures that brings together a ground-breaking group of products into one cohesive range. The system combines industry-leading fire safety (with up to Class A2-s1,d0 reaction to fire) with W1-rated resistance to water penetration and airtightness.

4

What products are included in the complete ARBOSHIELD Pro® range?
Alongside the innovative self-adhesive EPAM® perimeter seal, the complete system includes a Class A W1 Breather Membrane, a Class A Air & Vapour Control Layer, Class A High-Tack Sealing Tapes, and a Class B W1 Breather Membrane.

5

Which types of projects is the ARBOSHIELD Pro® range suitable for?
The system is ideal for both new build and refurbishment projects across commercial, industrial, residential, and retail buildings. Because of its consistency and ease of installation, it is also an excellent choice for modular and off-site factory-built construction projects.

6

What technical support is available for specifying the ARBOSHIELD Pro® system?
ARBO® offers full technical support for specification, including NBS and Autodesk Revit integration, project specification tools and direct access to ARBO Technical Services for advice on product selection, detailing and installation guidance.

Explore the ARBO® Product Family

Sealants

Sealants for reliable movement joint, perimeter and weatherproof sealing in a wide range of applications.

Weather Protection

Effective weather sealing solutions for interface applications, penetration sealing and structural joints.

Adhesives

Bonding solutions for secure and durable adhesion across façade and construction substrates.

Accessories

Caulking Guns, Nozzles, Knives, Scrapers, G Clamps etc.

Find your contacts

Regardless of whether you are an architect and planner, property developer, industry specialist, distributor, applicator or specifier – if you have any questions about our products, services or specific construction projects, please feel free to contact the CARLISLE® contact person in your area with your technical questions. Our experts will be happy to advise you.

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Main Applications

Class A W1 is Suitable for a wide range of building types where fire performance and vapour permeability are both required.

High-Rise Residential

Meets fire performance requirements for residential buildings over 18 metres (11 metres in Scotland).

Schools, Hospitals & Care Homes

Class A2-s1,d0 fire classification makes it suitable for schools, hospitals and other high-risk occupied buildings.

Modular Off-Site Construction

Compatible with modular build programmes and off-site construction methods.

SFS & Light Steel Frame Walling

Designed for use with light steel frame and structural framing systems (SFS) in both new-build and refurbishment.

ARBOShield Pro Class A Air & Vapour Control Layer
Read more
ARBOShield Pro Class B W1 Breather Membrane
Read more
ARBOShield Pro External Perimeter Class A membrane (EPAM)
Read more
ARBOShield Pro Class A High Tack Sealing Tape
Read more

Complete solutions for your façade challenges

The ARBOSHIELD Pro® fire-resistant systems range offers a fully compatible suite of membranes, seals, and adhesives. Whether for new builds, refurbishments, high-rise residential developments, or modular construction – our cohesive product family provides the highest level of safety, weatherproofing, and compliance for your projects.

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