Structural Steel Regulations in the UK: Codes, Standards & EN1090

Structural steelwork in the UK is covered by several layers of rules: the Building Regulations, the design codes engineers calculate to, the standards fabricators must make steel to, and the law on construction products. Here's how they fit together.

The Building Regulations

The Building Regulations 2010 require a building's structure to be safe. Approved Document A (structure) is the guidance on how to show that, and it points to the design codes below. Building control checks the engineer's calculations and inspects the work.

Other Approved Documents apply to steel too:

• Approved Document B (fire safety) sets how long structural steel must resist fire. That's why steel in houses and many commercial buildings is boxed in with fire-rated board or coated with intumescent paint.
• Approved Document K covers stairs, guarding and balustrades. See our glass balustrade regulations guide.

Wales and Scotland have their own equivalents.

Design codes

Eurocode 3 (BS EN 1993) is the current design code for steel structures, used with the UK National Annex and the other Eurocodes for loads. Most new steel design in the UK is done to Eurocode 3.

You'll still see older British Standards on drawings and calculations:

• BS 5950 was the main UK steel design code before the Eurocodes. It was withdrawn in 2010, but it's still common on older drawings, and some engineers still refer to it.
• BS 449 is older still, from the days of permissible-stress design. You're most likely to meet it when checking existing steel in an older building.
• BS 2573 covers cranes. It isn't a building steelwork standard, but it's sometimes searched alongside the others when crane beams and runways are involved.

Whichever code is used, the engineer's design sets the sizes, grades and connections. A fabricator makes steel to that design.

Making the steel: BS EN 1090

Since July 2014, structural steel components have had to be CE marked (or now UKCA marked in Great Britain) under BS EN 1090-1. That means the fabricator must run a factory production control system that's audited by an approved body, and supply a declaration of performance with the steel.

BS EN 1090-2 sets the technical requirements for how steel is fabricated and erected. It uses execution classes from EXC1 to EXC4. The designer chooses the class from how critical the structure is. Most buildings fall into EXC2. EXC3 covers more demanding structures. Our EN1090 and CE marking guide explains this in more detail.

Other standards you'll see on a specification

• Steel grades: hot-rolled sections are made to BS EN 10025, usually grade S275 or S355.
• Welding: the fabricator's welding quality system follows BS EN ISO 3834, and welders are qualified to BS EN ISO 9606-1.
• Bolts: structural bolt assemblies are made to BS EN 15048 (non-preloaded) or BS EN 14399 (preloaded).
• Corrosion protection: paint systems are specified to BS EN ISO 12944, and hot-dip galvanising to BS EN ISO 1461.
• Specification: many UK projects use the National Structural Steelwork Specification (NSSS), which sets out workmanship and tolerances for building steelwork.

Health and safety

Steel erection is construction work, so the Construction (Design and Management) Regulations 2015 apply. On site that means risk assessments and method statements, lift plans, and safe access for working at height.

What this means for you

• On a home project, you need a structural engineer's calculations and building regulations approval. The steel should come from a fabricator certified to BS EN 1090-1, with the paperwork building control may ask for. See do I need building regs for a steel beam.
• On a commercial project, the specification will name the execution class, the design code and the standards above. Check that your fabricator is certified to at least the execution class required.

Frequently asked questions

Is BS 5950 still allowed? It's withdrawn by BSI, so it's no longer maintained, and new designs are normally to Eurocode 3. Whether an older code is acceptable on a particular job is a question for the engineer and building control.

Does every steel beam need to be CE or UKCA marked? Structural steel components placed on the market should be, under BS EN 1090-1. Ask your supplier for the declaration of performance.

What execution class is J&N certified to? We're UKAS-approved to BS EN 1090-1 at Execution Level 3, which also covers EXC1 and EXC2 work. See our structural steelwork service, or get in touch.