Structural design decides what the structure must be and confirms that it is adequate. Modelling, detailing and drafting represent that design accurately, so it can be coordinated, fabricated and built. Responsibility for structural adequacy stays with the design engineer unless a contract explicitly assigns part of it, most often connection design, to another appropriately qualified party. Every detailing scope should state this in writing. (New to the subject? Start with what structural steel detailing is.)
Four activities defined
| Activity | What it produces | Core question |
|---|---|---|
| Structural design | Calculations, design drawings, specifications | Is it strong, stable and code-compliant? |
| Modelling | 3D representation (coordination or detailing model) | Does it fit and coordinate with other disciplines? |
| Detailing | Shop/assembly/single-part/erection drawings, schedules, NC data | Can it be fabricated and erected exactly as designed? |
| Drafting | 2D drawings prepared to a drawing standard from given information | Is the information clearly and correctly presented? |
These activities overlap in daily work, but the responsibilities do not merge automatically.
Responsibility matrix (typical; contract governs)
| Item | Design engineer | Detailer | Fabricator | Erector |
|---|---|---|---|---|
| Member sizes, loads, stability | Responsible | Represents | — | — |
| Connection design | Responsible, unless delegated | Selects only if permitted (see below) | Responsible if delegated to its engineer | — |
| Dimensional accuracy of shop drawings | Reviews for intent | Responsible | Responsible to its client | — |
| Fabrication quality | Specifies | — | Responsible | — |
| Erection method and temporary bracing | Specifies requirements | — | — | Responsible |
Connection design: three common arrangements
ANSI/AISC 303-22, the US Code of Standard Practice, requires the owner's designated representative for design to indicate one of three options for connections:
- 1Option 1: connections are fully designed and shown in the design documents.
- 2Option 2: an experienced steel detailer selects or completes connections using tables or schematic details from the design documents or reference manuals the design team allows.
- 3Option 3: connection design is delegated to a licensed engineer working for the fabricator, with criteria from the design team.
The same standard's commentary discourages requiring the shop and erection drawings to be signed and sealed sheet by sheet, because that "may serve to confuse the design responsibility". It is a practical reminder that the drawings and the design are different things.
What does shop drawing review cover?
When the design engineer reviews shop drawings, the review is normally a check that the detailing conforms with design intent. It is not a re-check of every dimension. Responsibility for dimensional accuracy and fit-up generally remains with the fabricator and its detailer. Contract wording and the governing standard decide the exact split, so read the review stamp wording and the specification carefully.
European and UK practice: the execution specification
On projects using BS EN 1090-2 (Execution of steel structures, Part 2: technical requirements), the designer specifies requirements through the execution specification. That includes the execution class, which ranges from EXC1 (least onerous) to EXC4. Clause 4.1.2 states: "If no execution class is specified EXC2 shall apply." The execution specification and contract define who designs connections and what documentation is required. Always confirm the current edition named in your project specification. CEN lists EN 1090-2:2018+A1:2024.
GCC owner specifications may reference American, European or client standards, sometimes in combination. The responsibility split has to be read from each project's documents.
How should responsibilities be written into the contract?
- State the connection option or arrangement for each connection type.
- Name who approves, who reviews and who checks, and what each review means.
- State that the detailer works from approved design information and raises discrepancies, rather than resolving them unilaterally. Our input checklist lists what to provide.
- Exclude calculations and certification from detailing scope unless they are separately agreed with authorised professionals.
- Define how design changes after issue are instructed and priced.
PetroHill's standard offer is modelling, drafting and detailing using engineering information from the responsible design team. Connection engineering, calculations, certification and approval are not included unless separately agreed with appropriately authorised professionals. See our codes, standards and responsibility matrix.
Frequently asked questions
If the engineer approves our shop drawings, are we covered for errors?
Generally, no. Approval confirms conformance with design intent. Dimensional accuracy usually stays with the fabricator and detailer. Check your contract.
Can a detailer "design" simple connections?
Under AISC Option 2, an experienced detailer may select connections from permitted tables or details. That is selection within limits set by the design team, not independent design.
Which standard applies in the GCC?
Whichever the project specification names. Confirm it for each project.
What are execution classes in EN 1090-2?
EN 1090-2 defines four execution classes, EXC1 to EXC4, with requirements becoming stricter from EXC1 to EXC4. The designer selects the class and states it in the execution specification. The detailer and fabricator work to that class; they do not choose it.
Next step
If you need detailing support with a clear responsibility boundary, review our codes and standards approach or clarify your package scope with us.
Related services
References
Technical sources consulted. Standards are paid documents; confirm clauses against the licensed edition named in your project specification.
- ANSI/AISC 303-22 · AISC (opens in a new tab)
- BS EN 1090-2 preview · BSI via ANSI (opens in a new tab)
- EN 1090-2:2018+A1:2024 · iTeh (CEN catalogue) (opens in a new tab)
- Specifying the right Execution Class · New Steel Construction (opens in a new tab)
