Structural Steel Detailing
Structural Steel Detailing Process: From Design Drawing to Fabrication
Walk through a practical steel detailing sequence: input review, modelling or CAD layout, connections, checking, approval, shop drawings and fabrication release.
A steel detailing process is a sequence of decisions, not a CAD file that grows until someone plots it. Teams that skip the sequence tend to discover missing openings, wrong grades and unapproved connections after plates have already been nested. That is fabrication delay dressed up as “a small revision.”
This article lays out a process that works for conventional structural steel and for many PEB projects: freeze the input, lay out the frame, resolve connections, issue an approval package, incorporate comments, then release shop information. The names of the sheets change by region and contract; the order of risk does not.
If your bottleneck is the repetitive approval-sheet stage rather than connection design, see how automation can reduce approval drawing time and the MBS Approval Package.
Stage 0 — Freeze the input, or say what is not frozen
Detailing against a moving design set is possible, but only if everyone agrees which sheets are “for information” and which are issued for detailing. Print a drawing list with revision letters on day one. Anything without a revision letter is not an input; it is a sketch.
- Collect structural, architectural and MEP backgrounds that affect steel
- Record the governing specification, bolt and weld standards, and connection responsibility
- List known hold points: crane data, equipment vendor drawings, facade brackets
- Agree the piece-mark and drawing-number system before the first sheet is created
- Name the checker and the approval reviewer so comments have an owner
Stage 1 — Layout the frame in plan and elevation
Layout is the first engineering act of detailing. You are confirming that grids, levels, slopes, ridges and bracing actually form a buildable frame. This is also when you catch a rafter that is too long for the mill, a brace that clashes with a door, or a column that sits on the wrong side of a grid.
Work in the same units and grid origin as the design model or drawing. If you will later move geometry from analysis into CAD, keep node and grid names traceable. The structural model to CAD workflow article covers that hand-off in more detail.
Stage 2 — Connections, typical details and exceptions
Once members have locations, connections decide shop cost. A clean typical moment connection repeated 80 times is cheaper than 80 “similar” details that each differ by 5 mm. Document the typical, then list exceptions on the framing plan so the checker is not hunting through every piece sheet.
| Connection type | Decide early | Common hold-up |
|---|---|---|
| Simple shear | Bolt grade, hole type, cope rules | Insufficient edge distance after cope |
| Moment / end plate | Plate thickness source, weld vs bolt | Stiffener clashes with slab or haunch |
| Bracing gusset | Workpoint, pack plates, eccentricity | Brace clashes with purlin or girt |
| Base plate | Anchor layout vs foundation drawing | Anchor projection vs grout gap |
Stage 3 — Approval package before shop release
On most building jobs the reviewer does not want every clip angle at the first submission. They want to confirm geometry, member sizes, typical details, bracing and any connection that affects design. That is the approval set. Issuing full shop drawings before that review invites double work. See what approval drawings are.
Stage 4 — Comment incorporation and shop drawings
Comments are not a nuisance; they are the point of approval. Log each comment, assign it, and mark whether it changes geometry, a typical detail, or only a note. Then issue shop drawings and CNC data from the revised model or CAD files. Do not keep an “approval model” and a “shop model” that slowly diverge.
- Cloud only the change, and keep a revision letter on every affected sheet
- Update the BOM and bolt list in the same cycle as the drawing
- Tell purchasing which items are released for mill order versus still on hold
- If a comment contradicts the specification, raise it instead of silently picking one
Stage 5 — Fabrication support
Detailing does not end at issue. Fitters will ask about grain direction on a plate, whether a hole can move 10 mm, or how to handle a mill substitution. Those questions should come back through the same drawing, not through a chat message that never reaches the checker.
A practical workflow
- Issue an input register with drawing numbers and revision letters.
- Lay out grids, columns, rafters, beams and bracing and clash against openings.
- Agree typical connections and list exceptions on the plans.
- Prepare the approval package and transmittal.
- Log comments, revise, and re-issue with revision letters.
- Release shop drawings, BOM, bolts and CNC/nesting data.
- Support fabrication questions through the controlled drawing, not side emails.
Engineering tips
- Release mill steel only for members whose length and grade are stable.
- Keep one live drawing list. Multiple Excel trackers are how sheets get forgotten.
- If you automate approval sheets, automate the index at the same time.
- Photograph or screenshot each transmittal so you can prove what was sent.
Common mistakes
Detailing connections before the architectural openings are stable
A door moved 300 mm can obsolete a bay of girts and a wind-post connection. Hold those zones explicitly.
Using the design drawing as the erection drawing
Design drawings lack piece marks, shipping orientation and field-bolt notes. Erectors should not have to reverse-engineer them.
Skipping a checker because the job is “small”
Small jobs still have wrong hole gauges. A two-hour check is cheaper than a truck of misdrilled beams.
Letting CNC files drift from the PDF
If the shop burns plates from DSTV/NC files, those files are the drawing. They need the same revision control as the PDF.
Checklist
- Input register complete and dated
- Layout checked against latest architectural backgrounds
- Typical details issued with a stated range of use
- Approval package has cover, index, notes, plans, elevations
- Comment log exists before the second issue
- Shop drawings share marks with the BOM
- Hold items are visible on the drawing list
- Fabrication questions are filed against a sheet number
Frequently asked questions
How long does steel detailing take?
It depends on tonnage, connection complexity, how stable the design is, and whether approval is a separate stage. A more useful question is which hold points still exist. Unfrozen crane data or facade brackets will dominate the calendar more than CAD speed.
Can detailing start before the design is fully approved?
Layout can start from an issued-for-design set if the risk is accepted and hold zones are marked. Do not mill-order or fabricate from unverified geometry.
Where do PEB jobs differ from conventional steel?
PEB work often uses manufacturer software such as MBS for analysis and member sizing, then a highly standardised approval package. The process stages are the same; the typical details and sheet structure repeat more often.
When is a drawing ready for the shop?
When comments that affect geometry or connections are closed, the revision letter is current, and purchasing/CNC data match the sheets. “The reviewer did not reply” is not closure unless the contract says so.
Where this leaves the work
If you remember only one thing, remember the order: freeze input, lay out geometry, resolve connections, approve, then manufacture. Reversing that order is how steel gets cut twice.
Use the detailing checklist before each issue, and keep common detailing errors next to the checker’s desk.
This article provides general educational information. Project-specific structural design, calculations and drawings should be reviewed by appropriately qualified engineering professionals and checked against applicable project requirements and standards. StruTools does not replace engineering judgement or professional design review.