If you manufacture structural steel or aluminium components, BS EN 1090 may be an important requirement for your business. Yet many organisations still have questions about what the standard requires in practice, particularly when it comes to understanding Execution Classes (EXC) and how they affect certification requirements.
Whether you’re a fabricator, welder, quality manager or part of an HSEQ team, understanding BS EN 1090 can help you demonstrate compliance, improve consistency and maintain confidence in the products you place on the market.
What is BS EN 1090?
BS EN 1090 is the standard that governs the fabrication, assembly and conformity assessment of structural steel and aluminium components placed on the market.
Manufacturers supplying structural components within the scope of BS EN 1090 are required to:
- Implement a Factory Production Control (FPC) system
- Use qualified welding procedures and competent welding personnel
- Demonstrate compliance through a UK Approved Body or EU Notified Body, where applicable
- Apply the appropriate product marking requirements (UKCA and/or CE marking) for the intended market
Failure to comply can result in legal enforcement, project delays, product withdrawal and reputational damage.
What Are Execution Classes (EXC)?
Execution Classes define the level of quality control, technical requirements and inspection required for a structure based on its complexity, intended use and the potential consequences of failure.
There are four Execution Classes within BS EN 1090.
EXC1: Simple, Low-Risk Structures
EXC1 applies to straightforward structures with relatively low consequences of failure, such as:
- Agricultural buildings
- Simple storage structures
- Basic handrails and barriers
EXC2: The Most Common Execution Class
EXC2 is the execution class most commonly specified across the UK construction sector.
It typically applies to:
- Residential developments
- Commercial buildings
- Office blocks
- Car parks
- Standard structural steel frames
EXC3: Higher-Risk or More Complex Structures
EXC3 is generally used where structures are subject to higher loads or where failure could have more significant consequences.
Examples include:
- Bridges
- Stadia
- Industrial facilities
- Large public buildings
EXC4: Exceptional, Safety-Critical Structures
EXC4 is reserved for highly complex or safety-critical applications where the consequences of failure are severe.
Examples may include:
- Long-span bridges
- Major infrastructure projects
- Power generation facilities
- Special engineering structures
For BS EN 1090-2 (steel structures), the execution class is typically specified by the designer or client. For aluminium structures covered by BS EN 1090-3, EXC2 is commonly adopted where no execution class has been specified, although the designer or client should always confirm the appropriate classification.
Why EXC2 Is So Important
Because EXC2 is the most commonly specified execution class, many fabricators underestimate the level of control required to achieve and maintain compliance.
Typical requirements include:
- Qualified welders
- Approved welding procedures (WPS)
- A Responsible Welding Coordinator (RWC)
- Material and consumable traceability
- Inspection and testing activities
- Non-destructive testing (NDT), where required
- Documented Factory Production Control procedures and records
While EXC2 is often viewed as the standard execution class, it still requires robust controls around welding, traceability, inspection and documentation. These requirements help ensure structural integrity, consistency and confidence in the finished product.
A Legal Requirement for Relevant Structural Components
Manufacturers placing structural steel and aluminium components covered by BS EN 1090 onto the market must comply with the relevant conformity assessment requirements and product marking obligations.
Depending on the market being supplied, this may involve UKCA marking, CE marking or both.
Failure to comply can result in:
- Product withdrawal or recall
- Project delays
- Financial penalties
- Enforcement action
- Reputational damage
- Increased safety risks
The requirements apply to organisations of all sizes, from small fabrication workshops through to large-scale manufacturers.
Taking the Next Step
Whether you’re preparing for certification for the first time or looking to strengthen an existing Factory Production Control system, understanding your execution class requirements is an important step towards demonstrating compliance and maintaining confidence in your products.
As a UK Approved Body, ISOQAR provides BS EN 1090 certification services, helping manufacturers demonstrate compliance with the standard’s requirements and support access to relevant markets.
