Steel construction class - how to choose it and what does it mean for safety, durability and investment costs?

14/10/2025

Classes of construction, defined in EN 1090 standardare a key element in the design and construction process. The correct choice of EXC class is not just a formal requirement, but has a real impact on the safety of people and the environment, the reliability of the structure's operation, as well as the investment costs and its operation.

What are the EN 1090 construction classes?

Standard EN 1090-1 and EN 1090-2 are European documents setting out rules for the design, manufacture and installation of steel and aluminium constructions. As part of this legislation, the so-called EXC (Execution Classes)which classify structures in terms of potential risks, the level of difficulty of implementation and the necessary degree of control.

EN 1090 construction classes include four levels:

EXC1 - the simplest designs with low risk of use,
EXC2 - typical building structures,
EXC3 - constructions of high technological and social importance,
EXC4 - the most complex, high-risk buildings i engineering structures.

Selecting the right class should be part of an early project, taking into account loads, the place of application and the significance of the object.

What does each EXC performance class mean?

EXC class	Description of construction according to EN	Examples of use	Requirements
EXC1	Simple structures with steels with a strength class of up to 275 MPa, mainly with fixed loads	Small agricultural halls, conservatories, buildings up to two storeys	Basic control, simplified documentation
EXC2	Structures of medium complexity, S700 endurance	Production halls, support structures, office buildings	Standard ZKP procedures, welding control, compliance with the standard
EXC3	Structures under dynamic load or of major importance	Road and railway bridges, stadiums, large industrial installations	Strict quality control, documentation according to EN 1090-2, NDT tests
EXC4	Structures with the highest significance and hazard potential	Power plants, high-rise buildings, military facilities	Highest requirements, full documentation, supervision by notified body

Why is the EXC class so important?

The selection of an EXC class affects all elements of the construction process - from design to execution and acceptance. Classes determine the level of quality control, the requirements for welding, material testing, technical documentation and the factory production control (FPC) system.

Incorrect class assignment can lead to:

serious failures or damage to the structure,
threats to human life and the environment,
failure to obtain conformity assessment,
rejection by building supervision.

How to choose the right performance class?

Class selection should take into account:

Complexity and function of construction - The greater the risk and importance, the higher the class.
Type of loads - whether they are only static or also dynamic (e.g. vibrations, impacts).
Strength class of steel - EXC2 and above often require steel grade S355 - S700.
Environment and risk potential - whether the structure is in a public place or exposed to aggressive conditions.

Example: For a standard warehouse it is often enough to EXC2 classbut if there are industrial installations exposed to vibrations, it is worth considering EXC3.

Construction of steel and aluminium structures in accordance with the standard

Each plantwho wants to legally steel or aluminium construction according to EN 1090, must:

implement a QC system in line with EN ISO 3834 i EN 1090-1,
pass a certification audit by notified body,
have documented quality control procedures,
ensure compliance with the requirements EN 1090-2 in terms of performance.

Only then can the structure receive CE marking and be legally authorised in the EU.

Importance for the investor - safety, costs and sustainability

Selecting an EXC class is not just a technical matter - it is a decision that directly affects the investment costs, the timetable and operational risk.

Lower class (e.g. EXC1) means simpler procedures and lower costs, but limited design options.
Higher classes (EXC3 and EXC4) involve additional costs for documentation, testing and supervision, but provide a higher level of safety, sustainability i damage resistance.

For many industrial projects, particularly those exposed to dynamic nature of the work, class selection EXC3 is the standard. For critical infrastructure - only EXC4.

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Summary

System construction classes according to EN 1090 is one of the most important pillars of quality and safety in steel construction. Selecting the right EXC class - from EXC1 to EXC4 - should be a conscious decision on the part of the designer and developer, depending on the intended use of the facility, the degree of risk and the expectation of sustainability.

Construction of steel and aluminium structures in accordance with this standard guarantees not only legality and compliance with formal requirements, but also real protection of people and the environment from the effects of potential failures. Remember: the right choice of performance class is the foundation of a sound investment.

FAQ - Frequently asked questions

1. what does the EXC classification mean and how many performance classes are there?

The EN 1090 standard divides structures into four performance classes: EXC1, EXC2, EXC3 and EXC4. Each of these specifies requirements for the design, manufacture and installation of structural elements, depending on the complexity, potential hazard and intended use of the building.

2. which objects are included in the EXC1 performance class?

The EXC1 execution includes structural elements of minor safety importance, such as agricultural buildings, sheds or conservatories. These structures or load-bearing structures are mainly subjected to permanent loads, made of steel with a strength class of up to 275 MPa and have simplified design and inspection requirements.

3. how to assign a building to the correct performance class?

The categorisation of structures into particular performance classes depends on factors such as the type of building, its function, level of loading, social or technological importance and material specification. The choice of class is made by the designer, in accordance with the guidelines of EN 1090-2 and a risk analysis.

4. does every part of the structure have to have the same EXC class?

No, it is possible to assign different classes to different parts of a structure. For example - main structural elements or load-bearing structures may require class EXC3, while auxiliary elements may only need to be designed according to EXC2.

5 Who sets the guidelines for the EXC class?

The guidelines for EXC classes are contained in EN 1090-2 and their application is supervised by a notified body within the conformity assessment system. Designers, engineers and contractors must take these requirements into account at every stage of the project.

6. Do the performance classes have an impact on investment costs?

Yes. The higher the performance class, the more stringent the requirements for documentation, materials and inspection, which translates into higher design and manufacturing costs. Therefore, each construction group should be assigned to the appropriate class according to the actual level of risk.