An EN 1090-2 execution class, from EXC1 to EXC4, sets how strictly a fabricator must build, inspect and document a steel structure. Choosing the right one, then checking that your fabricator actually holds it, is the first decision on any imported steelwork package. This guide explains how to choose the class, why it limits who can legally build the work, and how to verify a fabricator's class in a single step.
What EN 1090-2 execution classes are, from EXC1 to EXC4
EN 1090-2 grades fabrication into four execution classes, EXC1 to EXC4, and the class rises with the consequence of a failure. EXC1 is the lightest regime, used for low-risk work such as sheds, fences and simple agricultural frames. EXC2 is the common default for ordinary commercial and light industrial buildings, including offices and standard warehouses.
EXC3 covers high-consequence structures: bridges, stadiums, high-rise buildings, and the process and power plant framing that carries heavy equipment. EXC4 is the most onerous class, and it suits only the highest-hazard structures. According to Yu Hang, our welding coordinator, the class you name decides three things at once: how the shop qualifies the welds, how much of the steel gets tested, and how much documentation follows the job. That is why it belongs on the first page of a specification, not in a footnote. Buyers often assume EXC2 out of habit, because it fits most ordinary buildings, then find at tender that the plant frame or the long-span roof they are really buying sits a class higher. You can see how we hold this class on our certifications page.
How the execution class is determined
Three inputs from the Eurocodes decide the execution class: the consequence class of a failure, the service category of the loading, and the production category of the fabrication. The designer or consulting engineer sets the class, component by component if the parts of a structure differ. It is an engineering decision, not a marketing choice.
The consequence class asks what a failure would cost in lives and money, and it runs from CC1 for low consequence to CC3 for high consequence such as a stadium roof or a plant that many people work under. The service category separates mostly static loading from fatigue and seismic loading. The production category reflects the steel grade and how the shop makes the joints. Combine the three and EN 1090-2 points to a class. The standard allows pre-qualified welding procedures for EXC2 in ordinary structural grades up to S355; at EXC3 and above, or with higher-grade steel, it calls for full welding procedure qualification. Yu Hang, our welding coordinator, says a buyer can always ask the design engineer which class applies, and to which parts, rather than leave it to the fabricator to assume. We set out how this plays out for a process pipe rack in our guide on how to specify and verify a pipe rack fabricator.
Why the class you specify limits who can build it
The class you specify also decides who is allowed to build the work, because a notified body certifies a fabricator's Factory Production Control for one execution class. Under EN 1090-1, a shop that holds only an EXC2 certificate cannot legally fabricate EXC3 or EXC4 steelwork. Naming EXC3 therefore narrows the field to shops that hold an EXC3 certificate from a notified body.
This matters because many suppliers still quote on high-consequence work they have no certificate to produce, and the gap only surfaces at inspection or on site, once the steel is cut. EUROCERT certifies our own Factory Production Control to EXC3, so we take on the process-plant structures, pipe racks and long-span space frames that sit above the EXC2 line, alongside the standard EXC2 buildings. According to Yu Hang, the honest question to ask any bidder is simple: which execution class does your FPC certificate carry, and who issued it. The answer for our own shop sits on our long-span structures page.
How to verify a fabricator's execution class in one step
To verify an execution class, ask for the Factory Production Control certificate number and the notified body, then check it against that body's own records. A certificate is not a logo. It carries a number the issuer can confirm, which turns a claim in an email into a fact you can rely on. The declaration of performance, which the fabricator issues under EN 1090-1, names the execution class, the harmonised standard and the notified body on one page, so it is the fastest document to ask for first.
EUROCERT S.A. in Greece issued our EN 1090-2:2018 certificate 1128-CPR-10.09.0686 for execution class EXC3, valid until 13 March 2028. The attestation carries annual surveillance, and EUROCERT last surveilled the works on 5 March 2026, so an auditor re-checks the shop every year rather than signing it off once and forgetting it. According to Yu Hang, a buyer's inspector can confirm that certificate directly with EUROCERT before any steel is cut, and can ask for the declaration of performance that lists the class, the standard and the notified body. The numbers and the scan of the certificate sit on our certifications page.
The welding qualification behind the class: ISO 3834-2 and the welding coordinator
Above EXC1, the execution class rests on welding quality, so EN 1090-2 ties the class to a welding quality system and a qualified welding coordinator. ISO 3834-2 is the comprehensive tier of the welding quality standard, and it is the tier that EXC3 work calls for.
ISO 3834-2:2021 sets out the comprehensive requirements, and ISO 14731:2019 defines the tasks a welding coordinator must own. We hold ISO 3834-2:2021, certificate 10.09.0687, and our welding coordinator holds the International Welding Engineer (IWE) qualification under ISO 14731:2019. Our welding procedure qualification records cover processes 135 (MAG), 136 (FCAW) and 121 (SAW), at material group 1.2 and plate thickness up to 30 mm. Those records exist because EXC3 requires them, so a buyer's inspector can review the WPQRs at enquiry stage rather than take the welds on trust.
What changes on the shop floor as the class rises
Moving from EXC2 to EXC3 changes four things in the works, and each one adds cost and time that an honest quote has to carry. The welding procedures need full qualification rather than pre-qualified status. A qualified welding coordinator has to own the welding tasks from the drawing to the final weld. Non-destructive testing covers a wider share of the welds. The traceability that follows each piece of steel, from mill certificate to finished member, gets deeper.
According to Yu Hang, the most visible change is testing: at EXC3 an inspector expects volumetric non-destructive testing on a defined share of the full-penetration butt welds, not the light visual check that clears most EXC2 work. That is why an EXC3 price rarely matches an EXC2 price for the same tonnage, and why a quote that ignores the class deserves a second look. The testing extent, the welder qualifications and the inspection records all live in the same file that the execution class opens, and that file is the one a buyer's inspector should ask to see. Our capabilities page shows the shop that carries the EXC3 work.
Matching the class to the structure: how we map EXC to our own work
We map the execution class to the structure type directly: process-plant structures, pipe racks and long-span space frames run at EXC3, while standard workshops and warehouses run at EXC2. The split follows the consequence of a failure, so the heavy, high-consequence work carries the stricter class and the ordinary buildings carry the default. A boiler house frame for a biomass plant runs at EXC3, while the warehouse beside it, holding finished goods, runs at EXC2, even on the same site and the same purchase order.
The work we ship backs that mapping. Across 32 export projects in 14 countries, individual jobs have run from 5 to 2,000 tonnes, and the largest single job was a 2,000-tonne fly-ash retrofit for a power plant in the Philippines. The power work also includes a 12 MW coal-fired plant in Pakistan and a 10 MW biomass plant in Sri Lanka, the kind of framing that sits firmly in the EXC3 band. You can see the range on our pipe rack page, the steel workshops page and the full projects list. For how these structures are built to your drawings, see our guide to pipe rack types and fabrication.
A checklist before you specify the class
Before you fix the execution class on an enquiry, settle four points that decide the rest of the fabrication. First, determine the class from the consequence, service and production category, component by component. Second, for EXC3 and above, ask each bidder for the FPC certificate number and notified body, and check it.
Third, confirm the ISO 3834 tier and the welding coordinator's qualification. Fourth, check that the welding procedure qualification records cover your material group and plate thickness. According to Yu Hang, most of an enquiry comes down to three answers before the shop cuts any steel: the class, the certificate and the welding records. Send us your design drawings with the execution class marked, or ask us to confirm the class for your structure, and we will confirm the class, the lead time and the price in writing through our contact page.