EN 1090 Execution Classes (EXC1 to EXC4) Explained
EN 1090-2 execution classes EXC1–EXC4 explained: what they control, how they're chosen by consequence class and service category, and what they mean for fabricators and buyers.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: EN 1090-2 sets technical requirements for executing steel structures in four execution classes, EXC1 (least onerous) to EXC4 (most onerous). The class is selected by the designer based on consequences of failure, service conditions and production categories, and it determines requirements for materials, welding quality, NDT extent, tolerances, documentation and fabricator quality systems.
On projects designed to European practice, specifications often reference EN 1090-2 and an execution class. Understanding the classes helps buyers evaluate fabricators and costs.
The four classes
| Class | Typical application (general) |
|---|---|
| EXC1 | Low-consequence structures, e.g. simple agricultural buildings |
| EXC2 | Most buildings and general structures |
| EXC3 | Structures with high consequences or fatigue, e.g. stadiums, some bridges |
| EXC4 | Very high consequence structures, e.g. critical bridges and special structures |
The designer chooses the class using guidance in the Eurocodes (consequence class, service category and production category).
What the class controls
- Material traceability level
- Welding quality requirements (linked to EN ISO 3834 parts)
- Welding coordination personnel qualification
- Weld quality levels (ISO 5817 B, C, D)
- Extent of NDT (NDT guide)
- Geometric tolerances
- Surface preparation and documentation
Higher classes mean more inspection, documentation and cost.
Related EN standards
- EN 1090-1: CE marking and conformity assessment for structural components (EU context)
- EN ISO 3834: welding quality requirements
- EN ISO 9606 / 15614: welder and procedure qualification (WPS and PQR)
Buyer tips
- Confirm the execution class in the specification before tendering
- Ask fabricators for evidence of capability at that class
- Don't over-specify — EXC3 where EXC2 suffices adds cost
- American-practice projects use AISC 303/360 and AWS D1.1 instead (SBC 306)
See how to choose a fabrication company and structural fabrication.