A structural engineer’s design drawing tells you a beam exists, its size, and roughly where it goes. It does not tell a fabricator exactly where to cut, drill, and weld it, or tell a crew on site which piece goes where in what sequence. That gap — between design intent and physical, build-ready instruction — is exactly what steel detailing fills.
What steel detailing actually is
Steel detailing is a specialist area of structural drafting: interpreting architectural and structural engineering drawings to fully understand the design intent, then producing the detailed drawings, schedules, and instructions needed to fabricate, assemble, and erect every steel component. Design drawings from architects and engineers give the overall picture — general dimensions, spatial planning, member sizes — but stop short of the dimensional precision fabrication actually requires. A steel detailer’s job is translating that design intent into comprehensive, build-ready visual instructions, often also designing and calculating connections where the structural layout doesn’t fully specify them.
GA drawings: the big-picture roadmap
The first deliverable is the General Arrangement (GA) drawing, also called a marking plan or marking elevation. It shows the overall steel framework — column locations, beam layouts, levels, and key dimensions — so fabricators and site teams understand how the whole structure fits together before diving into individual-piece detail. Think of the GA as the map everyone refers to first; it’s also where each assembled piece gets its unique identification — the erection mark — that follows it all the way through fabrication, shipping, and installation.
Shop drawings: build-ready instructions for each piece
From the GA, detailers produce shop drawings (also called piece details, fabrication drawings, or manufacturing drawings) for individual members — beams, columns, braces, plates. These break each member down into exact instructions: dimensions, material specification, hole locations, cuts, connection and weld details, and a bill of materials. Shop drawings are what the workshop actually works from for cutting, drilling, fitting, and welding — they’re the difference between “a 6-metre beam” and a piece manufactured to the precision steel construction demands. Even small errors here — a misplaced hole, a wrong length — cause real delays and rework once a piece reaches site.
Erection drawings: putting it together on site
Once pieces are fabricated and shipped (with their erection marks punched or painted on), erection drawings guide the installation crew. They show the layout, orientation, and connections needed to assemble the fabricated pieces correctly and safely in the field, including sequencing and any temporary bracing or constraints needed during the build. Site teams rely on erection drawings as their basis of work to ensure every part goes in exactly as designed — and assembly drawings within this stage often detail the bolting or welding sequence needed for a safe, correct build-up.
Where modern detailing happens: software and BIM
Modern steel detailing is almost always done in specialized 3D modeling software — Tekla Structures and Autodesk Advance Steel are the two most common — rather than manually drafted, as it was decades ago. Working in 3D lets detailers build a digital model of the entire structure before fabrication begins, which is increasingly integrated with broader BIM workflows for clash detection and cross-discipline coordination. This is also where the detailer continually coordinates with architects, engineers, and contractors — verifying steel components match design intent, resolving issues before they reach the shop floor, and keeping the whole process moving smoothly.
Why this discipline matters so much
Without accurate detailing, even a perfectly engineered structure struggles to come together as intended. Steel construction demands a high level of dimensional accuracy, and detailing is the layer that actually delivers it — turning a structural engineer’s design intent into something a fabrication shop and an erection crew can execute without guesswork.
Part of our Steel Design & Detailing series. Next: bolted vs welded connections — pros and cons.