Structure of the Standard
EN 1090-1: Conformity Assessment
EN 1090-1 establishes the requirements for conformity assessment of structural components made from steel or aluminium, ensuring they meet the performance characteristics necessary for safe execution in construction works under the Construction Products Regulation (CPR). It applies to manufacturers, fabricators, and distributors who place these components on the market within the European Economic Area, mandating a systematic approach to verify compliance with technical specifications outlined in EN 1090-2 and EN 1090-3.[8] The standard emphasizes risk-based classification and verification processes to facilitate CE marking, thereby enabling free movement of products across EU member states.[8]
The standard refers to four execution classes (EXC1 through EXC4), defined in EN 1090-2 and EN 1090-3, which categorize structural components according to the potential consequences of failure, the type of structure, and associated risks. EXC1 represents the lowest level of control, suitable for components with minimal risk, such as non-load-bearing elements in low-consequence applications, while EXC4 demands the highest scrutiny for critical structures like bridges or high-rise buildings where failure could lead to severe safety hazards.[8] The assignment of an execution class is determined by the specifier based on factors including service category, production category, and corrosion protection, with detailed criteria provided in the material-specific parts of EN 1090.[8] Higher classes impose stricter manufacturing, inspection, and documentation obligations to mitigate risks effectively.[8]
Central to conformity assessment is the Factory Production Control (FPC) system, a documented framework that the manufacturer must implement to ensure ongoing compliance with the declared performance characteristics. The FPC includes detailed procedures for planning, controlling, and monitoring production processes, with mandatory records of inspections, tests, and non-conformities retained for traceability purposes.[8] Traceability is achieved through unique identification of components and materials, linking them back to certificates and test results, while internal audits—conducted at planned intervals—verify the effectiveness of the system, identify deviations, and drive corrective actions.[8] For execution classes EXC2 and above, the FPC must be certified by an independent notified body, ensuring impartial oversight.[8]
Conformity is assessed through Assessment and Verification of Constancy of Performance (AVCP) systems, ranging from System 1 to System 3, selected based on the execution class and risk level. System 1 involves comprehensive certification by a notified body, including type testing and initial factory inspection, suitable for the highest risks; System 2+ requires notified body certification of the FPC with continuous surveillance for EXC3 and EXC4; while System 3 relies on manufacturer-internal controls with product testing for lower classes like EXC1.[8] These routes ensure that the constancy of performance is verified against harmonized technical specifications, with surveillance intervals varying by class—annually for higher classes and up to every three years for lower ones.[8]
The Declaration of Performance (DoP) serves as the key document for declaring conformity, prepared by the manufacturer before placing the component on the market. It must include details such as the manufacturer's identification, product type, intended use, execution class, and specific performance values for essential characteristics, including load-bearing capacity calculated per relevant Eurocodes, fatigue strength, reaction to fire, and durability against corrosion.[8] The DoP format follows a standardized template, with any non-determined parameters marked as NPD (No Performance Determined), and it accompanies the CE marking to provide transparency to users and authorities.[8] This declaration integrates the material-specific rules from EN 1090-2 and EN 1090-3 to ensure holistic compliance.[8]
EN 1090-2: Technical Requirements for Steel
EN 1090-2:2018+A1:2024 establishes the technical requirements for the execution of steel structures, covering aspects from material selection to final inspection to ensure structural integrity, safety, and performance in accordance with execution classes defined in EN 1090-1. These requirements apply to the fabrication, assembly, and erection of steel components used in construction, with provisions scaled to the complexity and consequences of failure associated with each execution class (EXC1 to EXC4). The standard emphasizes traceability, quality control, and compliance with harmonized European product standards to facilitate CE marking under the Construction Products Regulation. The 2024 amendment updates cross-references, annexes, and includes new provisions such as minimum hold times before non-destructive testing.[2]
Material selection under EN 1090-2 mandates the use of steel grades conforming to EN 10025-2 through EN 10025-6 for hot-rolled structural steels, ensuring specified mechanical properties such as yield strength and ductility. Representative grades include S235 for general low-stress applications, S275 for moderate loads, and S355 for higher strength demands in load-bearing elements. Weathering steels, which form a protective oxide layer for corrosion resistance in atmospheric exposure, are specified per EN 10025-5, with grades like S355J0W suitable for bridges and outdoor structures without additional coatings. Stainless steel variants, offering superior corrosion resistance in harsh environments, must comply with EN 10088-4 for sheets/plates or EN 10088-5 for long products, such as austenitic grades like 1.4301 (304). All materials require factory production control certification and traceability documentation to verify compliance.[22][23]
Fabrication tolerances in EN 1090-2 are outlined in Annex B and categorized into essential tolerances for structural stability, functional tolerances for assembly and aesthetics (with Class 1 as default and Class 2 for tighter controls), and project-specific special tolerances. Geometric tolerances limit deviations such as straightness to no more than L/1000 of the member length (where L is the length), with a minimum of 2 mm, to prevent excessive distortion in beams and columns. Alignment tolerances ensure end-to-end squareness and parallelism, typically within 1-2 mm for bolted connections, while surface conditions require flatness deviations of ≤ 3 mm over 1 m for plates to maintain load distribution and fatigue resistance. These tolerances are verified post-fabrication using measurement methods like straight edges or levels, with deviations corrected if they exceed limits.[24]
Welding processes in EN 1090-2 must be executed by qualified personnel and supervised by a welding coordinator, with procedures qualified per EN ISO 15614 to validate parameters for specific material thicknesses and joint types. Approved welding processes include arc welding (e.g., MAG, TIG) and resistance welding, selected based on the execution class and joint accessibility. Preheating is required for steels with higher carbon equivalents or thicknesses exceeding 10-20 mm to reduce hydrogen-induced cracking, with minimum temperatures ranging from 50°C for S355 to 150°C for quenched and tempered grades, controlled via thermocouples. Post-weld heat treatments, such as stress relieving at 550-650°C, are specified for thick sections or high-restraint welds to minimize residual stresses and improve toughness, particularly in EXC3 and EXC4 applications. All welds undergo visual inspection, with supplementary non-destructive testing as per the execution class.[22]
EN 1090-3: Technical Requirements for Aluminium
EN 1090-3 specifies the technical requirements for the execution of aluminium structures to ensure mechanical resistance, stability, and durability, tailored to the material's unique properties such as lower strength compared to steel and higher thermal conductivity.[26] It applies to components made from rolled sheet, strip, plate, extrusions, forgings, and castings, excluding those covered by other specific standards like cold-formed elements. Compliance with these requirements is essential for achieving the appropriate execution class as defined in EN 1090-1, including factory production control systems.[26]
Alloy selection under EN 1090-3 is governed by Section 5.4, which mandates the use of wrought aluminium alloys conforming to EN 573-3 for chemical composition and product forms. These alloys are categorized into heat-treatable and non-heat-treatable types, with heat-treatable alloys (such as those in the 6xxx and 7xxx series, e.g., EN AW-6061) strengthened through heat treatment processes to enhance mechanical properties, while non-heat-treatable alloys (such as 1xxx, 3xxx, and 5xxx series, e.g., EN AW-5083) achieve strength via work hardening. Temper designations, specified per EN 515, further define the alloy condition, including F (as-fabricated), O (annealed), H (strain-hardened), and T (heat-treated) states, ensuring suitability for structural applications. For instance, EN AW-5083 in the H116 temper is commonly selected for marine environments due to its corrosion resistance.[26][26]
Forming and bending requirements are outlined in Section 6.5, emphasizing the need to prevent cracking and maintain structural integrity given aluminium's ductility and sensitivity to deformation. Minimum bend radii are specified to avoid defects, varying by alloy series and thickness; for example, the 5xxx series typically requires a minimum radius of 1.5t to 3t (where t is the material thickness) to minimize cracking risks, with tighter radii possible for softer tempers but requiring verification through testing. These guidelines reference Annex F for geometrical tolerances and draw from EN 1999-1-4 for design considerations, ensuring that forming operations do not compromise the material's fatigue resistance or surface quality.[26][26]
Joining methods, particularly welding, are detailed in Section 7, with processes selected according to EN ISO 4063 to account for aluminium's high thermal conductivity and oxide layer. Common arc welding techniques include TIG (process 141) for precision on thinner sections and MIG (process 131) for higher productivity on thicker plates, both requiring pre-cleaning to remove oxides and qualified welding procedure specifications. Filler materials must match the parent alloy's properties as per EN ISO 18273 (Section 7.5), such as using EN ISO 5183 for welding 5xxx series to maintain corrosion resistance and strength; over-alloying is permitted to compensate for dilution effects. Distortion control is managed through a comprehensive welding execution plan (Section 7.2), incorporating techniques like balanced sequencing, clamping, and controlled preheating or interpass temperatures (up to 150°C for certain alloys) to mitigate residual stresses inherent to aluminium's expansion behavior.[26][26][26]
EN 1090-4 and EN 1090-5: Cold-Formed Elements
EN 1090-4, currently in draft form as prEN 1090-4:2025, establishes technical requirements for the execution of cold-formed structural steel members and profiled sheeting used in applications such as roofs, ceilings, floors, and walls.[27] This standard focuses on manufacture through processes like cold forming, cutting, holing, and limited welding, while also addressing installation aspects including site conditions and personnel qualifications.[28] It applies to structural classes I through III as defined in EN 1993-1-3, covering elements like purlins, profiles, perforated sheeting, and hollow sections.[27]
Key provisions in EN 1090-4 include specifications for roll-forming tolerances, outlined in Annex D, which define essential and functional tolerances to ensure dimensional accuracy in sheeting and members during production.[27] Local buckling checks are integrated by referencing the design rules of EN 1993-1-3, emphasizing the stability of thin-walled sections prone to distortion under load.[27] Fastener connections, such as self-tapping screws and blind rivets, require specific edge distances and spacings to maintain structural integrity, particularly in lightweight assemblies.[27] Fatigue considerations for these elements are handled under EN 1993-1-3 for static and seismic loading scenarios.[27]
In contrast to standards for hot-rolled steel under EN 1090-2, EN 1090-4 places greater emphasis on the challenges of thin-sheet stability and local buckling due to the material's reduced thickness and forming-induced stresses.[27] This includes heightened attention to fastener connections and fatigue resistance in applications like cladding, where cold-formed elements enable lighter, more efficient designs but demand precise control over thin-sheet behavior.[29]
EN 1090-5, in draft as prEN 1090-5:2025, provides analogous requirements for the execution of cold-formed structural aluminium profiled sheeting and elements for similar building applications, aligned with the EN 1999 series.[30] It covers manufacture via cold forming and installation, excluding welded sections which fall under EN 1090-3, and supports combinations with steel elements for hybrid structures.[30]
The standard specifies strain limits during forming through reference to EN 1999-1-4 design provisions, ensuring material integrity without excessive work hardening in aluminium alloys.[30] Joint efficiency factors are addressed via tolerances and fastener specifications, including self-tapping screws and blind rivets with defined edge and field spacings to optimize load transfer in connections.[30] Like EN 1090-4, it prioritizes thin-sheet stability and fatigue for lightweight uses such as cladding, differing from broader aluminium rules in EN 1090-3 by focusing on formed profiles rather than extruded or plate-based components.[30]
Both prEN 1090-4:2025 and prEN 1090-5:2025 are expected to achieve full harmonization under the Construction Products Regulation by 2026, enabling CE marking and conformity assessment in line with EN 1090-1.[31] This transition builds on the general technical requirements from EN 1090-2 and EN 1090-3 for steel and aluminium, respectively, while tailoring rules to cold-formed specifics.[20]