On UK projects, steel connection design is either retained by the structural engineer or delegated to the steelwork contractor. Both are valid, but the contract must state which. When it's delegated, the engineer provides the design forces and the fabricator designs the connections to Eurocode 3, for the engineer to check.
The two models
Connection design is a defined responsibility, and on a steel job it sits with one of two parties:
- Retained by the structural engineer, who designs the connections and shows them on the design drawings
- Delegated to the steelwork contractor, who designs the connections from the forces the engineer provides
Delegated connection design is common on UK commercial steel. It plays to the fabricator's knowledge of how the steel will actually be made and erected, but it only works when the allocation is clear from the outset.
When connection design is delegated
If the fabricator designs the connections, the structural engineer still owns the overall design and must provide the design forces, or end reactions, for every member. The fabricator then designs the connections to BS EN 1993-1-8 (Eurocode 3), commonly using the SCI and BCSA ‘Green Book’ methods for standard connections. The engineer reviews and approves the result.
This is part of what good design and steel detailing delivers: connections that satisfy the engineer's forces and suit how the steel is fabricated and erected.
When the engineer retains it
If the engineer designs the connections, they appear on the design drawings and the fabricator works to them directly. There's less for the fabricator to design, but the engineer must issue complete connection details before fabrication can be fully priced and built.
Why it must be allocated in writing
The single most common cause of dispute and delay on steel packages is an unclear connection-design responsibility. The National Structural Steelwork Specification (NSSS) exists partly to make this allocation explicit. Settle it in the contract and the enquiry, so nobody assumes the other party is doing it.
What this means for your quote
Tell the fabricator at enquiry stage whether connection design is retained or delegated. It changes what gets priced and who carries the design risk. Our guide to what to send for a quote covers it, and you can send your drawings whenever you're ready.
Common questions
- Can the steelwork contractor design the connections?
- Yes, when connection design is delegated. The structural engineer provides the design forces, the contractor designs the connections to BS EN 1993-1-8 (Eurocode 3), and the engineer reviews and approves them.
- What standard are steel connections designed to?
- Steel connections are designed to BS EN 1993-1-8 (Eurocode 3). Standard connections are commonly designed using the SCI and BCSA ‘Green Book’ guidance, which sets out compliant methods for simple and moment connections.
- Who checks delegated connection design?
- The structural engineer responsible for the overall design reviews and approves the delegated connection design. Delegation moves the design work, not the engineer's responsibility for the structure as a whole.