Fire resistance of membrane structures (PVC, PTFE, ETFE)

Tensile membrane structures are taking an ever larger share of contemporary architecture. They are lightweight, they let architects shape the building envelope freely, and they have a distinctive visual identity that conventional construction cannot replicate. Most of these structures are clad in one of three materials — PVC-coated polyester, PTFE-coated fibreglass, or ETFE foil. As they become more common, the question of fire safety naturally moves to the front of every project conversation. As specialists, we want to share what we know so you can make informed and safe design decisions.

Membrane materials and how they react to fire: PVC, PTFE, ETFE

Choosing the right membrane is the foundation. The decision drives not only the look and the durability of the structure, but also how it behaves in a fire. Three materials dominate the market: PVC, PTFE and ETFE. Each has unique characteristics that determine its reaction to flame and high temperature. At Abastran we work with all three on a daily basis when designing and installing tensile membrane and ETFE structures, so we know their specifics in detail.

PVC-coated polyester membranes are the most common, economical option. They are valued for good tensile strength and ease of welding, which lets us produce reliable, watertight seams. From a fire-safety standpoint, PVC is classified as flame-retardant — typically class B-s1, d0 under EN 13501-1. This means the material self-extinguishes once the ignition source is removed. The important caveat: at high temperatures PVC can release toxic gases, which must be considered in the overall fire strategy.

PTFE-coated fibreglass — Teflon on a glass-fibre weave — is a different category altogether. It is extremely durable, UV-stable, chemically resistant, and self-cleaning. From a fire perspective the key fact is that PTFE is non-combustible, classified A2-s1, d0. It does not melt and does not produce flaming droplets, which significantly raises the safety level of the structure. ETFE foil, used mainly in pneumatic cushions, is celebrated for its transparency. Like PVC, ETFE is flame-retardant (typically B-s1, d0). In a fire it melts and forms openings — which can actually help vent smoke from the building, but also carries the risk of dripping hot material.

Fire resistance in regulation: standards and classes you need to know

To assess how a membrane structure will behave in a fire, we use European standards that also apply in Poland and across the EU. The key document is EN 13501-2, which defines how building elements are classified for fire resistance. The classification is expressed as a combination of letters and numbers. Three letters matter most: R (load-bearing capacity), E (integrity) and I (insulation).

• R (load-bearing capacity in fire): how long a structural element — say, a membrane roof on a steel frame — keeps its shape and load-bearing capability under a fire load without collapsing.

• E (integrity in fire): the ability of a barrier to prevent fire and hot gases from passing through to the protected side.

• I (insulation in fire): how effectively the element keeps the temperature on the unexposed side from rising too far. The point is to prevent ignition of other materials and to protect people on the safe side of the barrier.

The number next to these letters (e.g. RE 30, REI 60) is the time in minutes for which the property is maintained under a standard fire test. Whether you are designing a roof or a wall, the specific R/E/I requirements differ. Detailed test methods for specific applications are defined in standards such as EN 1365-2 (for roofs) and EN 13381-1 (for fire protection systems). Interpreting these designations correctly and choosing the right class is the key to a safe project.

How to read a fire-resistance certificate

A fire-resistance certificate is a critical document, but you need to know how to read it. Certificates are issued by accredited testing laboratories. They state the exact fire-resistance class (e.g. REI 60), but the small print matters. The class always refers to a specific tested system: a particular membrane, a particular insulation, a particular supporting structure and a specific installation method.

The most important rule: do not assume that a certificate obtained for one system automatically covers a different system, even if the differences look minor. Changing the insulation thickness or the membrane fixing method can completely change the fire behaviour. Always make sure your design solution is identical to the one described in the certificate. Check the validity date too — standards and technologies evolve. If you have any doubts about how to interpret a document or how to specify a system for your project, get in touch with us — the Abastran team is happy to share what we know.

PVC vs PTFE vs ETFE — fire performance compared

Which membrane is the safest in a fire? A direct comparison shows clear differences. The clear leader is PTFE-coated fibreglass. It is non-combustible (class A2-s1, d0), which means it essentially does not participate in the fire. It does not melt, does not drip, and does not feed the flame. It is the right choice when maximum passive safety is the priority — public venues with high occupancy, for example.

PVC and ETFE are both flame-retardant materials (typically B-s1, d0). They burn with difficulty, release little smoke, and do not produce flaming droplets in standard tests. Their behaviour in a real fire is different from PTFE, however. PVC softens and melts, and — more importantly — can release toxic hydrogen chloride. ETFE also melts, forming openings that can help with smoke venting, but also creating a risk of hot material dripping. The choice between PVC and ETFE depends on the project specifics: the potential consequences (smoke, toxicity, dripping) and the fire-resistance requirements of the entire envelope.

Membranes in practice: examples and lessons learned

How do membranes hold up in real situations? Take a few examples. On large stadiums and concert halls, you will most often find PTFE membranes on the roof. Why? Because PTFE is non-combustible. Even if a fire breaks out beneath the canopy, the membrane itself does not become extra fuel. That is critical for the safety of thousands of people during evacuation.

ETFE foil on roofs and facades has an interesting property: when it melts, it forms openings. Designers sometimes use this as part of a smoke-venting strategy, letting smoke and hot air escape through the roof. The price you pay for this is the risk of dripping molten plastic — escape routes have to be designed accordingly. PVC membranes, while flame-retardant, can release toxic smoke in an intense fire. In facilities with special safety requirements their use may be restricted or require additional protection. Every case is different and requires its own risk analysis.

The reaction-to-fire class of the material itself is not the whole story — the fire resistance of the entire building barrier (R/E/I), including how the membrane works with the supporting structure and any insulation, is what counts. Investing in certified, proven solutions and working with experienced designers and contractors who specialise in membrane technology is the best guarantee of a building that is not only modern and functional, but above all safe for its users.

If you are facing a design challenge involving membrane, steel or ETFE structures, get in touch with Abastran — together we will find an optimal and safe solution. Regular monitoring of the technical condition of the structure ensures it keeps its properties for many years.