EN 1090 EXC3 Explained: The Gold Standard for Structural Steel
Deep dive into EN 1090 Execution Classes. What separates EXC3 from EXC2, certification requirements, and why it matters for DACH procurement.
Editorial author: Steel-Hub.eu
Published:
Updated:
TL;DR
- ▸EN 1090 is the European standard for CE-marking structural steel; the execution class (EXC1-EXC4) decides how much inspection and documentation the job carries.
- ▸EXC3 versus EXC2 means more supplementary NDT (e.g. 20% instead of 10% of transverse butt welds; visual inspection stays 100%), full traceability, welding procedures qualified by test, ISO 3834-2 and weld quality level B.
- ▸EN 1993-1-1 Annex C sets the class: CC2 under static loads is EXC2, while CC3 and CC2 under fatigue or seismic loading are EXC3 - crane runways, antenna masts, bridges.
- ▸Specifying below what the authority expects is the most expensive saving available: rejected documentation costs more than the class ever did.
What is EN 1090?
EN 1090 is the harmonized European standard for the fabrication and assembly of steel and aluminium structures. It is mandatory for any structural steel product bearing the CE mark within the European Economic Area.
The standard defines four Execution Classes (EXC1 to EXC4), each demanding increasingly rigorous quality controls, weld inspections, and material traceability.
Execution classes: EXC1 to EXC4
- EXC
- Execution class stated in the project specification.
- 1–4
- Class identifiers, not dimensions or load ratings.
- 3
- EXC3 is the focus of the comparison below.
EXC2 vs. EXC3: The Critical Difference
| Requirement | EXC2 | EXC3 |
|---|---|---|
| Supplementary NDT, transverse butt welds | 10% | 20% |
| Material traceability | Batch level | Individual piece |
| Weld procedure tests (WPQR) | Basic | Full qualification |
| Weld quality level (EN ISO 5817) | C | B |
| FPC surveillance by notified body | 1–2–3–3 years | 1–1–2–3–3 years |
| Welding quality system (EN ISO 3834) | Part 3 | Part 2 |
Why EXC3 Matters for DACH
In German, Austrian and Swiss practice the structural engineer specifies the execution class and the building authority (Bauaufsicht) checks the evidence. Under EN 1993-1-1 Annex C a CC2 structure under static loads is EXC2; EXC3 applies to CC3 and to CC2 structures under fatigue or seismic loading — exactly where DACH buyers source heavy steel: crane runways, antenna masts and infrastructure.
Industrial Halls
Crane runways and fatigue-loaded halls → EXC3; static CC2 halls → usually EXC2
Telecom Towers
Antenna masts and towers (wind-induced fatigue) → typically EXC3
Power Infrastructure
HV lattice towers → class per grid-operator specification (often EXC2), not per voltage
Architectural Steel
Visible AESS structures → EXC per the structure, plus the AESS finish category
Evidence in a Steel-Hub EXC3 Package
- ✓EN 1090-2 EXC3 — third-party factory production control evidence on request
- ✓ISO 3834-2 — Comprehensive welding quality management
- ✓ISO 1461 — Hot-dip galvanizing for corrosion protection
- ✓NDT to EN 1090-2 — UT/MT reports for the specified weld extent
- ✓EN 10204 3.1 — Individual material certificates for full traceability
Verifying a supplier before award? Our EN 1090 EXC3 compliance hub has the 8-point certificate verification checklist.
EN 1090 execution class FAQ
What is the difference between EXC2 and EXC3?
EXC3 raises routine supplementary NDT on transverse butt welds from 10% to 20% (visual inspection stays 100%) and adds full traceability, welding procedures qualified by test (WPQR), ISO 3834-2 comprehensive quality requirements and weld quality level B. Notified-body surveillance of the factory production control also tightens: years 1, 2 and 4, then every three years.
Which execution class does my project need?
The structural engineer assigns it per EN 1993-1-1 Annex C from the consequence class and the loading: CC2 under static loads is EXC2; CC2 under fatigue or seismic loading and CC3 are EXC3; EXC4 is reserved for extreme failure consequences. Crane runways and antenna masts are typical EXC3 jobs, while an ordinary CC2 hall without fatigue loading is usually EXC2.
Is EN 1090 the same as CE marking?
CE marking of structural steelwork is issued under EN 1090-1 on the basis of factory production control certified by a notified body. EN 1090-2 defines the technical execution requirements and the execution classes. In practice you need both: the class governs how the steel is made and documented, the CE mark and Declaration of Performance accompany the delivery.
Does EXC3 cost more than EXC2?
Yes - more testing, more documentation and tighter surface preparation all carry cost. The comparison that matters is not EXC3 versus EXC2 but EXC3 versus a rejected documentation package on a structure specified as EXC3, which costs far more than the class difference and delays acceptance.