BS EN 1090 is the standard that sits behind almost all UK structural steelwork. When a fabricator says it works “to BS EN 1090”, it means the steel was produced under a controlled, audited system rather than to a verbal promise of good workmanship. The standard comes in two parts that do different jobs: BS EN 1090-1 covers declaring fabricated components as construction products, and BS EN 1090-2 covers how those components are actually executed. This guide explains both, what they demand of a fabricator, and why it matters when you are buying steel.
T C Rowan is CE approved and works to the BS EN 1090 execution standards across its structural steelwork and wider steel fabrication projects. The detail below is general guidance, not a substitute for your structural engineer or building control body. For the related CE and UKCA marking question, see our CE marking and UKCA guide.
What BS EN 1090 actually is
BS EN 1090 is the UK adoption of the European standard for the execution of steel and aluminium structures. For structural steelwork it is the reference point that defines what “compliant” means: not the fabricator’s own judgement, but a published, auditable set of requirements.
It is split into two parts that people often conflate:
- BS EN 1090-1 is the harmonised standard that lets a fabricator declare structural steel components as construction products, apply the conformity mark and issue a Declaration of Performance.
- BS EN 1090-2 is the technical standard for the execution of the work: fabrication, welding, tolerances, inspection and erection.
Understanding the split is the key to understanding the standard. One declares the product; the other governs how it is built.
BS EN 1090-1: declaring components and Factory Production Control
BS EN 1090-1 is the part that turns a fabricated beam, column or frame into a declared construction product. It allows the fabricator to apply the conformity mark and issue a Declaration of Performance, which is the formal written statement of the steelwork’s declared performance.
The engine behind 1090-1 is Factory Production Control, usually shortened to FPC. FPC is a documented system covering how the workshop:
- sources steel and keeps it traceable to its certificates
- qualifies its welders and follows approved welding procedures
- inspects the work and records what was found, rather than assuming
- controls the whole process so the declared performance is genuinely achieved
A fabricator operating a 1090-1 system is being audited against that paperwork. That is the practical difference between a controlled workshop and one that simply describes itself as careful. Factory Production Control is also what makes material traceability on request a real, deliverable thing rather than a marketing line.
BS EN 1090-2: execution and fabrication requirements
If 1090-1 is about declaring the product, BS EN 1090-2 is about how the steel is actually executed on a given project. It is the technical heart of the standard and covers the requirements for fabrication and erection: the welding, the bolting, the dimensional tolerances, the inspection regime and the level of documentation expected.
BS EN 1090-2 is where the demands scale up or down with the job. A simple domestic frame and a heavily loaded commercial structure are both fabricated to 1090-2, but the stringency applied to each is set by the execution class.
Execution classes EXC1 to EXC4 in brief
BS EN 1090-2 defines four execution classes, EXC1 to EXC4, in rising order of stringency. EXC1 is the least demanding and EXC4 the most. The higher the class, the tighter the control over welding qualification, inspection, tolerances and traceability.
The class is not chosen by the fabricator. The specifying engineer assigns it by combining the consequence of failure, the type of loading (static against fatigue, seismic or impact) and how the structure is produced and used. An everyday domestic or light commercial frame typically sits around EXC2, while large, highly loaded or safety-critical structures move up to EXC3 and, in special cases, EXC4.
For the full breakdown of how each execution class is decided and what it changes on site, see the execution-class section of our CE marking and UKCA guide. The short version: expect the execution class to be stated in your project specification, and expect your fabricator to work to it.
What working “to BS EN 1090” actually requires
Saying a workshop works to BS EN 1090 is shorthand for a set of concrete obligations. In practice it means:
- Qualified, coded welders following approved welding procedures, not ad hoc technique
- Material traceability, so the steel on your project can be tied back to its certificates on request
- Recorded inspection, where checks are documented rather than assumed
- A Factory Production Control system that an auditor can examine
- A Declaration of Performance issued for the declared components
These are the same controls whether the current marking rules call for a CE or UKCA mark, because the underlying engineering discipline does not change. A genuine structural fabricator carries this whole chain; a thin operator tends to avoid the subject because it cannot evidence any of it.
CE, UKCA and where 1090 fits
It is worth being careful here, because BS EN 1090 is often discussed alongside CE and UKCA marking. The UK’s position on CE versus UKCA marking for construction products has changed repeatedly since Brexit, and the deadlines have moved more than once. CE marking has continued to be recognised rather than being switched off on a fixed date.
So do not treat either mark as the single settled answer. Confirm what your specific project requires with your building control body and the latest official government guidance at the time you specify. What stays constant underneath both marks is BS EN 1090 itself: the standard, the Factory Production Control and the execution class are the real engineering, and a good fabricator works to them regardless of which mark the current rules call for.
Why it matters to a buyer
For load-bearing and structural work, BS EN 1090 is your evidence that the steel was made properly. It lets you, your engineer or building control ask to see a Declaration of Performance, check the execution class against the specification and confirm the welding and traceability behind the job. Beam sizing and the execution class both need a structural engineer’s calculation, and load-bearing work needs Building Control sign-off. The grade of steel matters too, which is why our guide on steel grades S275 and S355 sits alongside this one.
T C Rowan is a single fabricator from drawing to final bolt, working to BS EN 1090 with in-house design, its own Banbury workshop and its own erection team. If you want the 1090 and execution-class questions answered against your actual drawings, get in touch for a free quote.
Frequently asked questions
What is BS EN 1090?
BS EN 1090 is the UK adoption of the European standard that governs how structural steel and aluminium components are declared and executed. It comes in two main parts: BS EN 1090-1 covers declaring fabricated components as construction products and the Factory Production Control system behind that, while BS EN 1090-2 sets the technical requirements for the actual fabrication and erection of steel structures. Together they define what working to a recognised standard means rather than leaving quality to a fabricator’s own opinion.
What is the difference between BS EN 1090-1 and BS EN 1090-2?
BS EN 1090-1 is about the product: it lets a fabricator declare structural steel components against the harmonised standard, apply the conformity mark and issue a Declaration of Performance, all underpinned by a Factory Production Control system. BS EN 1090-2 is about the work: it sets the execution requirements for fabrication and erection, including welding, tolerances, inspection and the execution class. In short, 1090-1 declares the component and 1090-2 governs how it is made and installed.
Does my project need a BS EN 1090 fabricator?
Load-bearing and structural steel (beams, columns, portal and braced frames) is treated as a construction product, so it is normally fabricated to BS EN 1090 and the execution class set by your engineer. Lighter, non-structural metalwork may not carry the same requirement. Because the rules around marking have shifted since Brexit, confirm what your specific project needs with your structural engineer and building control body, and expect any genuine structural fabricator to work to BS EN 1090 regardless.
How do I check a fabricator is BS EN 1090 compliant?
Ask three things. First, can they confirm they operate a Factory Production Control system and provide a Declaration of Performance for the steelwork. Second, can they show welding qualifications and procedures, plus material traceability and recorded inspection. Third, have they confirmed the execution class against your engineer’s specification. A fabricator working to BS EN 1090 will answer all three readily; one that avoids the subject usually cannot.