Is UPVC Cladding Fire Resistant? The Complete Guide

This blog post examines whether uPVC cladding is fire resistant, looking at its fire rating classification and how it performs when exposed to flames.

Is uPVC Cladding Fire Resistant?

Credit: EnviroBuild

PVC cladding is not naturally fire-resistant and can char and fall away when exposed to fire. It has a fire rating of C or D, meaning it is combustible.

However, there are Class 1 Fire Rated cladding options available that are resistant to the spread of flames.

Key Points

• Standard uPVC cladding has a Class C or D fire rating, meaning it is combustible.
• uPVC will char and melt when exposed to high heat or flame.
• Fire-rated uPVC cladding options are available to resist fire spread.

Our Opinion

In my expert opinion, standard uPVC cladding is not fire-resistant.

While it can achieve Class B fire ratings in some cases, it remains combustible to some degree.

For buildings that require non-combustible cladding, fire-rated uPVC or other Class A1 materials would be a better choice.

Proper fire testing and certification are essential for any cladding product.

What Is the Fire Rating of uPVC Cladding?

It has a fire rating of Class C or D, meaning it is combustible. The fire ranking classification for cladding materials ranges from A1 to F, with A1 being the least flammable.

Some uPVC cladding can be formulated to reach a Class B fire rating. However, there are Class 1 Fire Rated cladding options available that are more resistant to the spread of flames.

• Class C and D uPVC cladding are combustible and not resistant to fire spread.
• Standard uPVC cladding has a poor fire rating, ranging from C to D.
• Special formulations can improve uPVC to Class B, but Class A1 products are much more fire-resistant.
• Alternatives like fire-rated mineral fibre cement cladding have higher fire ratings up to A1.

So in summary, regular uPVC cladding ranks low for fire resistance at Class C or D. While it’s possible to improve the fire rating somewhat, uPVC remains combustible and vulnerable to fire spread. For optimal fire resistance, Class A1-rated non-combustible cladding is a better choice.

How Does uPVC Cladding Compare to Composite Cladding for Fire Resistance?

Credit: EnviroBuild

Composite cladding often uses materials like wood or aluminium composites that have better fire resistance than uPVC. Here’s a comparison:

• uPVC cladding is combustible and has a Class C or D fire rating. Composite wood cladding is normally Class B or C.
• Aluminium composite cladding can achieve Class A2 or even A1 fire rating, making it very fire resistant.
• During a fire, uPVC softens, sags, and falls away as it burns. Composites like aluminium are non-combustible and maintain integrity in fire.
• Standard uPVC ignites easily at low temperatures around 300°C. Fire-rated composites can withstand over 1000°C.
• Toxic smoke from burning PVC is a hazard in fires. Non-combustible composites do not produce smoke or toxic fumes.

The bottom line is composite cladding with materials like fire-rated aluminium can achieve much higher fire resistance than combustible uPVC. Composites maintain strength and limit fire spread far better. For buildings needing non-combustible, fire-resistant cladding, composite is a safer choice than standard uPVC.

Is uPVC Cladding Combustible?

Yes, standard uPVC cladding is combustible and can burn in a fire. Here’s why:

• uPVC stands for unplasticised polyvinyl chloride, which contains a high amount of PVC resin. PVC is inherently flammable.
• Tests show that uPVC ignites easily when exposed to flames or heat. It can begin burning at temperatures around 300°C.
• When heated, uPVC softens and sags as it decomposes. The material cannot maintain its strength or integrity in a fire.
• As uPVC burns, it releases dense smoke containing toxic fumes like hydrogen chloride, carbon monoxide, and dioxins.
• Standard uPVC cladding achieves a Class C or D fire rating. This means it is combustible and does not limit the spread of flames.
• Building codes classify uPVC as a combustible cladding material, unlike non-combustible options like aluminium and fire-rated composites.

While formulations exist to improve fire resistance, regular uPVC cladding burns readily when exposed to high heat or direct flame. This combustibility makes it less ideal for buildings needing non-combustible, fire-safe exteriors. Safer alternatives like aluminium or fire-rated composite cladding are available.

Does uPVC Cladding Meet UK Fire Safety Regulations?

Standard uPVC cladding may not meet current UK fire safety regulations for certain buildings. Here’s a look at the rules:

• England and Wales – The Building Regulations require cladding on high-rise residential buildings over 18 metres tall to be of limited combustibility or better. Standard uPVC does not meet this level of fire performance.
• Scotland – Scottish building standards mandate non-combustible cladding for high-rise domestic buildings and hospitals. Again, regular uPVC cladding does not comply as a combustible material.
• Northern Ireland – In NI, cladding on tall residential buildings must achieve an A2-s1, d0 classification, indicating limited combustibility. Standard uPVC cladding is typically Class C or D.
• While rules focus on high-rises, best practice suggests using fire-resistant cladding on any building where life safety is paramount. Hospitals, care homes, schools etc may opt for non-combustible or fire-retardant materials.

In summary, standard uPVC cladding does not meet the highest levels of fire performance mandated on certain buildings. Safer options like fire-rated composite cladding may be preferred, especially for high-rise residential. Always check the latest regulations for your project.

How Does uPVC Cladding Behave in a Fire?

When exposed to fire, uPVC cladding can pose risks. Here’s an overview of how it behaves:

• Melts rapidly – The vinyl in uPVC starts to soften around 80°C. By 200°C it becomes very soft and can melt, dripping flaming plastic that spreads the fire.
• Burns intensely – PVC is made of carbon and chlorine. When burned, it releases a dense black smoke containing toxic hydrogen chloride gas.
• High calorific value – PVC has a very high heat of combustion, releasing around 20MJ/kg when burned. This provides a significant fuel source for the fire.
• Falls from the facade – As uPVC melts and burns, it can become detached from the facade and fall away. This exposes more fuel to the flames.
• Difficult to extinguish – PVC keeps reigniting after fire suppression. It requires prolonged cooling to extinguish as it insulates itself while burning fully.

In summary, uPVC provides a readily ignitable fuel source that burns intensely and can significantly contribute to fire spread. Non-combustible or fire-retardant options are safer choices where fire performance is critical.

FAQ

Is uPVC cladding fireproof?

No, standard uPVC cladding is not fireproof. It can burn and melt when exposed to high heat or flame.

Is uPVC fire-rated?

Yes, uPVC cladding is given a fire rating based on fire tests. Common ratings are Class C or Class D, which means it is combustible to some degree.

Does my cladding need to be fire-rated?

In most countries, external cladding on buildings over a certain height is required to meet minimum fire rating standards. Check your local building regulations.

What do you put behind uPVC cladding?

uPVC cladding is installed over a waterproof membrane, insulating material, and structural sheathing on the exterior walls of a building.

Conclusion

Standard uPVC cladding is not fire resistant and can burn and melt in a fire. It typically has a Class C or D fire rating, meaning it is combustible to some degree. While uPVC cladding alone is not fireproof, there are fire-rated uPVC products available. The fire rating of cladding is an important consideration, especially for tall buildings. Overall, is uPVC cladding fire resistant? No, standard uPVC cladding will not resist fire.