Fire Rating Standards for GRP in Construction: Class 2 Explained
Introduction
Fire safety remains a non-negotiable factor in every construction project. Whether the setting is public infrastructure, industrial facilities, or residential access areas, materials must meet stringent fire performance criteria before they can be specified. For Glass Reinforced Plastic (GRP), one of the most common requirements in the UK is achieving Class 2 fire performance under BS 476 Part 7.
While GRP is often chosen for its corrosion resistance, low maintenance, and high strength-to-weight ratio, its fire rating can determine whether it is viable for certain applications. Understanding what Class 2 means, how it is achieved, and where it is applicable ensures that contractors can use GRP with confidence in fire-sensitive environments.
Understanding BS 476 Part 7
BS 476 Part 7 is a British Standard that measures the surface spread of flame for materials used in building construction. The classification ranges from Class 4 (highest spread of flame) to Class 1 (lowest spread of flame). Class 2 materials allow only limited flame spread across their surface, making them acceptable for many external and internal applications.
In practical terms, Class 2 GRP can be safely used in:
● Public walkways, bridges, and platforms
● Rail station access points and trackside installations
● Utility platforms and substations
● Coastal infrastructure where safety is critical
How GRP Achieves Class 2 Performance
Fire-retardant GRP is manufactured using resins formulated with halogen-free additives designed to slow ignition and reduce the spread of flames. During pultrusion or moulding, a surface veil can be incorporated to improve fire resistance and limit heat transfer. Unlike untreated timber, GRP will not continue to burn once the ignition source is removed, and unlike concrete, it does not spall under high temperatures. However, correct specification remains essential — standard grades of GRP without fire-retardant additives will not achieve Class 2 performance.
Compliance in Construction Environments
Construction teams must ensure that the GRP products they install are certified to the correct fire performance for their intended use. This is especially important in sectors where public safety is a priority or where insurance requirements dictate specific ratings.
Examples include:
● Poole’s Wharf pedestrian bridge refurbishment, where GRP Deck 500 panels were manufactured to Class 2 and installed to ensure the upgraded surface met slip resistance and fire safety standards.
● Network Rail’s use of GRP mesh fencing in public access areas, where Class 2 compliance provided additional safety assurance.
Verification and Certification
For contractors, it is critical to obtain and review the manufacturer’s test certificates to confirm compliance with BS 476 Part 7 Class 2. Certificates should reference the specific product, resin system, and manufacturing batch where applicable. This not only supports building control sign-off but also protects the contractor in the event of future compliance queries.
Why Class 2 Matters to Contractors
From a construction perspective, specifying Class 2 GRP is not just about meeting regulations — it is also about reducing future risk. If materials fail to meet required fire performance, replacement or remedial works can be costly, disruptive, and damaging to reputations.
By understanding the fire performance requirements at the design and procurement stage, and ensuring that certified Class 2 GRP is delivered to site, contractors can build with confidence that the installation will meet safety expectations from day one.
Conclusion
GRP can meet demanding fire safety requirements when manufactured and specified correctly. Class 2 under BS 476 Part 7 remains one of the most widely accepted ratings in UK construction, providing assurance that the surface spread of flame is limited.
For contractors, knowing what Class 2 means — and how to verify it — is key to ensuring that GRP is both safe and compliant in fire-sensitive applications. When combined with GRP’s other benefits, such as durability, light weight, and corrosion resistance, Class 2 fire performance makes it a strong contender in construction projects across multiple sectors.
