Understanding EN 13501-1 and Why It Matters for illbruck Membranes

Understanding EN 13501-1 and Why It Matters for illbruck Membranes

Creating high-performance building envelopes requires membranes that deliver airtightness, watertightness, and verified fire performance. With increasing regulatory pressure particularly on high-rise and higher-risk buildings manufacturers must evidence compliance with EN 13501-1, the European standard for reaction to fire classification.

This article explains how EN 13501-1 works, why it matters, and how selected illbruck membranes meet these requirements through robust system level testing.

What Is EN 13501-1?

EN 13501-1 is the harmonised standard that classifies construction products according to their reaction to fire. It evaluates how a material contributes to:

• Fire growth
• Flame spread
• Heat release
• Smoke production
• Flaming droplets

EN 13501-1 assigns a primary classification from A1 to F, along with two additional indicators:

Primary Classes

• A1 - Will not contribute to fire growth.
• A2 – Will not significantly contribute to fire growth.
• B – Minimum acceptable class for most façade membranes or "relevant membranes" in high-rise construction.
• C, D, E – Increasing levels of contribution to fire.
• F – No performance determined.

There are also two additional indicators which contribute to the reaction to fire.

These are:

• s1, s2, s3 – Smoke production
• d0, d1, d2 – Flaming droplets / particles
• s1 – Limited smoke production
• s2 – Medium smoke production
• s3 – No requirements
• d0 – No flaming droplets
• d1/d2 – Limited or unrestricted flaming droplets

Why The Standard Matters

High-rise and higher-risk buildings must comply with Approved Document B (Fire Safety), which uses EN 13501-1 classifications to ensure that façade and internal membranes do not contribute to fire spread. So for membranes to be used on

Which illbruck Products Meet EN 13501-1?

A wide range of illbruck membranes are tested in accordance with EN 13501-1, meeting the minimum Class B requirement for use in practical on-site applications. This ensures the membranes deliver reliable, verified reaction-to-fire performance across typical façade and building-envelope installations.

For example: 

• ME020 FR Window & Door Sealing Membrane achieves B-s2,d0, providing a user-friendly, quick-to-install solution suitable for general façade applications.
• ME050 FR Breather Membrane achieves A2-s1,d0, placing it among the highest-performing fire-rated membranes and making it suitable for high-rise or higher-risk buildings where strict fire performance criteria apply.

Overall, illbruck membranes are designed and tested to ensure dependable fire safety performance, giving confidence that they meet the standards required for compliant installation. Full fire resistance details are on each individual membrane.

✅Class A Fire Rated Membranes

• Class A1 - ME055 FR Breather Membrane
• Class A1 - ME060 A1-Membrane Pro Air and Vapour Control 
• Class A2 - ME050 FR Breather Membrane (ALU)
  
  

✅Class B Fire Rated Membranes

• Class B - ME007 FR Window & Door Sealing Membrane HD
• Class B - ME006 FR AVCL (Class B) | illbruck UK 
• Class B - ME020 FR Window & Door Sealing Membrane | illbruck UK

✅Fire Rated Sealants SP025 Fire Membrane Adhesive

System Testing: Why It’s Essential

Membranes often rely on adhesives, tapes, or integrated self-adhesive layers. EN 13501-1 requires that: The membrane + adhesive must be tested as a system,

• Applied as intended on a representative substrate,
• Ensuring classification reflects actual on-site performance.

This prevents situations where a membrane alone is compliant, but the adhesive layer compromises fire behaviour.

illbruck’s fire-tested membrane range such as ME050 A2-s1,d0 and ME020 self-adhesive Class B membranes offers contractors and specifiers the reassurance they need for both regulatory compliance and best-practice installation.

“Fire safety cannot be an afterthought. By testing systems rather than components, we ensure our membranes perform exactly as expected in real-world applications.”- Steve Wild, Technical Services Consultant Tremco CPG

Find out more about our fire rated membrane range here Fire Rated Membranes | illbruck UK.

If you’d like guidance and more information on how our membranes meet with compliance, contact the Illbruck team.