Self-Adhesive Breather Membrane

Class B – EN 13501-1

The OBEX CORTEX 0521FR is a Class B fire-classified, self-adhesive breather membrane engineered for external wall and façade applications. This advanced membrane integrates a fire-classified, self-adhesive backing and breathable, and airtight layer, offering a fully compliant solution in line all UK construction regulations.

Designed with a focus on ease of installation, superior performance, and compliance with construction standards, the OBEX CORTEX 0521FR sets a new benchmark in the field of breather and vapour permeable membranes for external applications. Its innovative features ensure it stands out as the superior option for professionals seeking reliable and effective building envelope solutions.

Key Benefits

  • GOLDEN THREAD ALIGNMENT – Class B fire classified, independent of the substrate, for full compliance with Reg 7.
  • REDUCE WATER INGRESS ISSUES – Rigorously tested to EN 1928 achieving W1 water resistance for ultimate performance.
  • EASIER PROJECT SCHEDULING – 6 months UV resistance for optimum project scheduling flexibility.
  • SUITABLE FOR OPEN CLADDING – Also available in plain black for the ultimate solution behind open rainscreen cladding.
  • EASIER INSURANCE APPROVAL – Full 3rd party approval with internationally recognised KIWA BDA.
  • LESS WASTE & DAMAGES – Excellent scuff and tear resistance with a highly durable outer coating.
  • IMPROVED HEALTH & SAFETY – Ergonomically designed roll sizes to aid manual handling and reduce musculoskeletal issues.
  • COMPLETE PEACE-OF-MIND – 20 year warranty for full confidence in the integrity of the product.
  • PROMOTE YOUR OWN BRAND – Custom options available to elevate your brand’s visibility and enhance brand recognition.
  • UP TO 30% QUICKER INSTALLATION – Split release liner for faster and improved installation with greater control and accuracy.

Typical Applications Include:

For use on external façades, normally applied direct to the sheathing board to prevent water ingress and allow vapour to escape.

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  • 3rd Party Certified 3rd Party Certified
  • 6 Months Exposure 6 Months Exposure
  • 6 Months Outdoor 6 Months Outdoor
  • Class B Class B
  • Lightweight Lightweight
  • Breathable Breathable
  • Vapour Permeable Vapour Permeable
  • W1 - EN 13859-2 W1 - EN 13859-2
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Product Specs


1100mm or 370mm options






Black (OBEX Branded) or Plain Black

Technical Specs

Harmonised Standard

EN 13859-2

Fire Classification | EN 13501-1


Watertightness | EN 1928


Sd value | EN ISO 12572


Tensile Strength | EN 12311-2

Longitudinal: 255 N/50mm, Transverse: 180 N/50mm

3rd Party Approved

KIWA Approval

UV Resistance

6 Months


OBEX CORTEX 0521FR Installation Guide

Product Order Codes

Product CodeProduct DescriptionWidthLengthBox Quantity
20.0521.001OBEX CORTEX 0521FR Self-Adhesive Breather Membrane1100mm25m1 Roll
20.0521.002OBEX CORTEX 0521FR Self-Adhesive Breather Membrane370mm25m1 Roll

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