Debunking GRP Design Myths: Structural Capability and Safety Explained
Introduction
Glass Reinforced Plastic (GRP) has been part of the construction and engineering landscape for decades, yet misconceptions about its performance continue to influence design decisions. Some architects, engineers, and contractors still view GRP as a specialist or lightweight alternative rather than a material that can stand alongside steel, aluminium, and concrete in permanent works. These assumptions often stem from outdated experiences with early GRP products or a lack of familiarity with the latest technical standards and manufacturing techniques.
In reality, modern GRP offers a proven combination of structural strength, long-term durability, safety compliance, and environmental benefits. Manufactured to rigorous British and international standards, it is now a core material in applications ranging from pedestrian bridges and blast walls to offshore platforms and high-voltage substations. This article examines the most common myths surrounding GRP’s design capability and safety, using technical evidence and real-world examples from Engineered Composites to provide clarity for those making specification decisions.
Myth 1: GRP is not as strong as steel or aluminium
One of the most persistent beliefs is that GRP cannot match the structural strength of metallic alternatives. While GRP has a lower modulus of elasticity than steel, meaning it will flex more under load, this does not equate to weakness. Pultruded GRP profiles manufactured to BS EN 13706 E23 grade can achieve axial tensile strengths up to 240 MPa and flexural strengths in the same range. The tensile modulus is typically around 23 GPa, giving designers predictable performance for structural applications.
Rather than directly replacing steel on a like-for-like section size, GRP profiles are specified to meet the same load requirements with tailored dimensions and support configurations. The reduced self-weight — often up to 75% lighter than steel — can also lower the load on supporting structures, reduce installation equipment needs, and speed up build programmes.
A prime example is the rooftop helicopter landing pad at Tres Cruces Hospital in Spain, where GRP structural profiles replaced the steel alternative. The project team selected GRP due to strict weight limitations on the existing roof structure. Despite the lighter mass, the GRP framework delivered the required strength and stiffness to support emergency landings while also meeting fire safety requirements.
Myth 2: GRP lacks long-term durability
Some design professionals assume GRP will degrade more quickly than steel or concrete in exposed conditions. In reality, GRP’s corrosion resistance is one of its defining strengths. It will not rust, rot, or spall, and is unaffected by saltwater, most industrial chemicals, and UV exposure when manufactured with the correct resin systems and stabilisers. Properly specified GRP structures can deliver service lives in excess of 50 years with minimal maintenance.
This long-term performance is illustrated by the refurbishment of Poole’s Wharf pedestrian and cycle bridge in Bristol. The bridge, exposed to rain, frost, and heavy footfall, was upgraded using GRP Deck 500 panels, non-slip flat sheets, and decking strips from Engineered Composites. The quartz-gritted surfaces restored slip resistance, while the GRP’s inherent weatherproof qualities ensured the upgrades will remain effective for decades without the need for repainting or galvanising.
Myth 3: GRP cannot meet safety standards
Another misconception is that GRP cannot meet the fire, slip, and electrical safety requirements demanded in modern infrastructure. In fact, Engineered Composites’ structural GRP products can be manufactured with fire retardant resins to meet Class 2 fire performance under BS 476 Part 7. Slip resistance can be engineered to exceed BS 7976 standards, ensuring safe footing even in wet or oily conditions.
The non-conductive nature of GRP also makes it ideal for live electrical environments, where steel would require earthing systems and additional safety measures. This is particularly valuable in applications such as substations, rail environments, and telecoms installations. The GRP mesh fencing supplied for Network Rail is a clear example: the system provides robust track-end protection while remaining electrically insulating and free from the signal interference associated with metallic fencing.
Myth 4: GRP is unsuitable for permanent works
GRP is sometimes seen as a temporary or stop-gap solution rather than a material suited to permanent installations. This perception often stems from early use cases in temporary site walkways or modular structures, but modern projects demonstrate its suitability for permanent civil engineering works.
For the Alyth Substation in Scotland, part of a major power transmission upgrade, Engineered Composites supplied GRP palisade fencing to provide non-conductive, corrosion-resistant perimeter security. The system was designed to withstand decades of service in a high-voltage environment exposed to harsh weather, with the added benefit of low maintenance requirements. Its inclusion in a multi-million-pound critical infrastructure project underscores GRP’s capability as a long-term asset.
Myth 5: GRP is a ‘light duty’ material
A related myth is that GRP is inherently less robust than steel and therefore only suitable for light-duty applications. Modern pultrusion technology, strict quality assurance processes, and compliance with structural standards have completely changed the reality.
The blast wall at Copenhagen Kastrup Airport demonstrates GRP’s role in heavy-duty, safety-critical infrastructure. Here, GRP structural profiles were selected over steel to provide a corrosion-resistant, non-magnetic barrier capable of withstanding extreme coastal weather and meeting stringent aviation safety standards. The structure is designed for long-term resilience without the continual repainting and inspection that a steel equivalent would require.
Addressing misconceptions through proper specification
Many of the misconceptions about GRP arise from either outdated product performance or incorrect specification. When engineers and designers work with a supplier who can provide complete technical data, load tables, and test certificates, GRP can be confidently designed into projects alongside — and often in preference to — more familiar materials.
For example, BS EN 13706 defines the performance requirements for pultruded GRP profiles, giving designers a clear benchmark. Fire performance to BS 476 Part 7, slip resistance to BS 7976, and compliance with BS EN 4592 for industrial flooring all give assurance that GRP is a tested and regulated choice. By reviewing the relevant certificates and ensuring the correct grade is specified for the environment and loading, specifiers can remove uncertainty and make decisions based on performance rather than perception.
Engineered Composites provides full support for specifiers, including CAD drawings, structural calculations, and case study evidence across multiple sectors. Whether it is GRP gratings for industrial platforms, GRP handrails for walkways, or GRP box sections for framing, every product is backed by the data and documentation needed to satisfy technical and compliance requirements.
Conclusion
The belief that GRP is inherently weaker, less durable, or less safe than traditional materials does not stand up to technical scrutiny. When designed and specified correctly, GRP offers structural capability that meets demanding loads, service lives exceeding half a century, compliance with fire, slip, and electrical safety standards, and resistance to environmental degradation that metals cannot match without significant upkeep.
From rooftop helipads to coastal blast walls, GRP has proved its value in high-profile, high-performance applications across multiple industries. For engineers, architects, and contractors seeking to combine safety, longevity, and environmental responsibility, GRP is not just a viable alternative — it is often the superior choice.
Those making design decisions are best served by examining the evidence, understanding the material’s modern capabilities, and working with an experienced supplier like Engineered Composites to ensure their GRP specification delivers the full benefits available.
