Understanding EN 1090 & Execution Class 4: Your Guide to Quality and Compliance

The EN 1090 standard is the legal framework that governs the fabrication of steel and aluminium structures in the UK and Europe, ensuring they are safe and fit for purpose. 

As a specialist certified to Execution Class 4 (EXC4), the highest level of this standard, we at RMP Products live and breathe these principles. This guide breaks down what our accreditations mean for your projects and why choosing an EXC4, certified partner is critical for safety, sensitive applications. 

 

What are Execution Classes? A Simple Breakdown 

EN 1090 uses a risk-based system called Execution Classes (EXC) to match the level of quality control to the potential consequences of a structural failure. There are four classes: 

• EXC1: For structures with low risk, such as agricultural buildings like barns.    

• EXC2: The most common class, covering the majority of UK commercial and residential buildings. If no class is specified, EXC2 is the default.    

• EXC3: For structures with a higher risk, including bridges, stadia, and buildings over 15 floors.    

• EXC4: Reserved for structures where failure would have extreme consequences. This is the most stringent class, demanding the highest level of quality control and assurance.    

A supplier can only produce components for the class they are certified for and any classes below it. Our certification to EXC4 means RMP Products is qualified to handle projects at every level of risk, from the simplest to the most complex. 

 

Why Execution Class 4 is the Ultimate Mark of Quality 

Specifying EXC4 is a declaration that a structure is of national importance and that no compromise on safety is acceptable. It is reserved for projects where failure is not an option. 

Typical EXC4 Structures Include: 

• Major long, span bridges and critical rail & transport infrastructure.    

• Structures within nuclear power plants and other energy facilities.    

• Major stadiums and arenas with complex roofs, like Wembley Stadium.    

• Offshore platforms and critical industrial installations.    

 

What Does It Take to Achieve EXC4 Certification? 

Achieving EXC4 certification requires a profound commitment to quality that impacts every part of the manufacturing process. More than just an upgrade from EXC3; it’s a different philosophy of risk management. 

Here are the key pillars of EXC4 compliance: 

• A Rigorous Factory Production Control (FPC) System: This is a comprehensive, audited quality management system that governs every step, from reviewing an order to final delivery. For EXC4, this system must be integrated with the highest standards for welding quality (EN ISO 3834, 2).    

• Complete Material Traceability: Every single piece of steel, every plate and beam, must be traceable from its origin at the mill right through to the final component. This forensic level of detail is essential for accountability and is a hallmark of EXC3 and EXC4.    

• Stricter Fabrication and Machining Rules: To preserve the material’s integrity, certain cost, effective methods are forbidden. For EXC4, holes must be drilled, never punched, to prevent micro, cracks that could lead to fatigue failure. Tolerances are also tighter, demanding greater precision in manufacturing.    

• Advanced Welding Control: Welding is a “special process” where quality is built, in, not just inspected at the end. EXC4 demands a highly qualified Responsible Welding Coordinator (RWC), empirically proven welding procedures, and the highest weld quality acceptance criteria (Level B+).    

• Intensive Inspection and Testing: While all welds from EXC2 upwards require 100% visual inspection, EXC4 mandates a massive increase in supplementary Non, Destructive Testing (NDT). For the most critical welds, this can mean 100% of the joint is tested using methods like ultrasonic or magnetic particle inspection to find hidden flaws.    

 

Why Choose RMP Products for Your EXC4 Project? 

When your project demands the highest level of assurance, you need a partner who has already made the investment in quality, equipment and expertise. 

• Certified to the Highest Standard: We are UKCA Marked to EN 1090 Execution Class 4 and certified to BS EN ISO 9001:2015 for quality management. This is your guarantee of compliance and quality. 

• Proven Track Record: For over 35 years, we have been a trusted supplier to the UK’s most demanding industries, including rail, nuclear, offshore and heavy engineering, working with leading OEMs like JCB and Caterpillar. 

• One, Stop, Shop Capability: We handle everything under one roof, from high, definition plasma and flame cutting to a full suite of CNC machining and finishing services. This reduces complexity, shortens lead times, and ensures quality control at every stage. 

• Removing Risk from Your Supply Chain: Our robust quality systems, full material traceability and meticulous inspection processes ensure every component we deliver meets the exacting requirements of EXC4 projects. 

 

Ready to discuss your next safety, critical project? Contact us today for a partner you can trust.