Understanding Fire Ratings of Steel Cladding Finishes: Galvanised vs. Plastisol vs. Polyester Paint
When choosing the right steel cladding for your project, performance and appearance often take centre stage — but fire safety is just as important. At Accord Steel Cladding, we supply a wide range of steel sheeting finishes, each with its own characteristics, durability, and fire performance.
In this post, we’ll take a closer look at the fire ratings of four common finishes we offer: Galvanised, Plastisol-coated, Polyester-painted, and Powder-coated steel.
🔹 Galvanised Steel Cladding
Galvanised steel is simply steel coated with a layer of zinc to protect it from corrosion. Because the coating is metallic, there are no combustible components — which means galvanised steel offers excellent fire resistance.
Fire Rating: Non-combustible
Reaction to Fire Class (EN 13501-1): Class A1
Key Benefit: Does not contribute to the spread of flame or emit toxic smoke.
Galvanised sheets are often chosen for agricultural, industrial, and internal applications where fire resistance and longevity are priorities.
🔹 Plastisol-Coated Steel Cladding
Plastisol finishes are made by coating galvanised steel with a layer of PVC (polyvinyl chloride) for added protection and colour. This makes the sheet tougher and more resistant to scratching or corrosion — ideal for external walls and roofs.
However, because the PVC layer is an organic material, it can soften or degrade under high heat. While the steel substrate remains non-combustible, the coating itself can melt or emit smoke if exposed to fire.
Fire Rating: Typically Class 0 / Class 1 (BS 476) or Class B-s2,d0 (EN 13501-1)
Key Consideration: The steel core won’t burn, but the PVC coating can contribute to smoke production under fire conditions.
Plastisol-coated sheets are still widely used thanks to their durability and visual appeal, but care should be taken in applications where fire resistance is critical (for example, near boundary walls or in public-access buildings).
🔹 Polyester Paint-Coated Steel Cladding
Polyester paint finishes (also known as PVF2 or simply “painted steel”) use an organic paint layer applied to galvanised steel. This type of coating is thinner than Plastisol and offers a smooth, decorative finish with good weather resistance.
In fire conditions, the polyester paint layer may burn off, but — as with Plastisol — the steel substrate remains structurally sound and non-combustible.
Fire Rating: Class 0 / Class 1 (BS 476) or Class A2-s1,d0 (EN 13501-1)
Key Benefit: Lower smoke and flame spread than thicker PVC coatings, with strong performance under fire exposure.
Polyester finishes are a great all-round choice for cost-effective, durable, and attractive cladding where a balance of performance and appearance is required.
🔹 Powder-Coated Steel Cladding
Powder-coated finishes use a dry powder — typically a polyester-based coating — electrostatically applied to galvanised steel and then cured to form a tough, protective surface. This creates a durable, fade-resistant finish available in a wide range of colours and gloss levels.
From a fire safety perspective, the powder coating layer is thin and contains very little organic material, meaning its contribution to combustion is minimal. The underlying steel substrate remains non-combustible, ensuring good overall fire performance.
Fire Rating: Class 0 / Class 1 (BS 476) or typically Class A2-s1,d0 (EN 13501-1)
Key Benefit: Excellent durability and colour stability with minimal smoke and flame spread under fire conditions.
Powder-coated steel is an ideal choice for architectural and decorative applications that demand both visual appeal and reliable fire performance.
🔹 Summary: Comparing Fire Performance
| Finish Type | Fire Rating (Typical) | Combustibility | Smoke / Flame Contribution | Best Suited For |
|---|---|---|---|---|
| Galvanised | A1 (non-combustible) | None | None | Internal linings, agricultural, industrial |
| Plastisol-Coated | B-s2,d0 / Class 0 | Low | Moderate | Roofs, walls, external cladding |
| Polyester-Coated | A2-s1,d0 / Class 0 | Low | Low | General-purpose cladding, decorative facades |
| Powder-Coated | A2-s1,d0 / Class 0 | Low | Very low | Architectural, decorative, high-visibility projects |
🔹 Final Thoughts
All steel cladding products supplied by Accord Steel Cladding meet strict quality and performance standards — but when it comes to fire safety, understanding the differences between finishes is key.
For maximum fire resistance, galvanised steel is the safest option.
For durable and attractive external finishes, Plastisol, Polyester, and Powder coatings all perform well, though each contains an organic layer that can affect fire classification.
If your project requires specific fire certification or compliance with Building Regulations (Approved Document B), our team can advise on suitable products and provide technical data sheets on request.
Need advice on choosing the right finish for your project?
Contact Accord Steel Cladding today — our experienced team is always happy to help with technical queries, samples, and product recommendations.
