What Are Shop Drawings?
Shop drawings are fabrication-ready documents produced by the steel detailer — not the engineer of record (EOR). They translate the EOR's design drawings into precise, shop-friendly instructions: exact dimensions, bolt patterns, weld symbols, piece marks, and material grades. The fabricator uses them to cut, drill, and assemble each steel member; the erector uses them to sequence and install the structure in the field.
The Drawing Set at a Glance
A typical shop drawing package for a structural project includes several drawing types, each serving a distinct purpose:
- Anchor Bolt Plans — locate cast-in-place bolts in the foundation; issued early so concrete work can proceed
- Framing Plans — overhead views showing column grid layout and beam placement at each floor level
- Elevation Views — side-profile views of moment frames, braced frames, or exterior wall framing
- Column Schedules — tabular or graphical breakdown of column sizes, base plates, and splices
- Assembly Drawings — detail sheets showing how individual members connect, including weld symbols and bolt callouts
- Piece Mark (Detail) Drawings — one sheet per unique fabricated component, showing exact dimensions for cutting and drilling
- Bill of Materials (BOM) — complete list of all members, plates, bolts, and hardware
Understanding Piece Marks
Every unique steel member receives a piece mark — a short alphanumeric code stamped or painted on the member during fabrication. Common conventions: columns often start with 'C' or 'W' (for wide-flange), beams with 'B', braces with 'BR', and miscellaneous plates with 'PL'. If two members share the same piece mark, they are identical and interchangeable. If a mark has a suffix like 'B' or 'R' (for 'bent' or 'reverse'), the member is a mirror image of the base piece.
Reading Dimensions and Tolerances
Dimensions on shop drawings are typically given to the nearest 1/16" for member lengths and 1/32" for hole locations. Work-point-to-work-point (WP-to-WP) dimensions define where the theoretical centerlines of intersecting members meet — always verify whether your dimension is to the work point, the face of the member, or the edge of a cope. AISC Fabrication and Erection tolerances (AISC Code of Standard Practice Chapter 6) govern acceptable deviations and are the governing reference for any RFI related to fit-up.
Weld and Bolt Callouts
Weld symbols follow AWS A2.4 conventions. The arrow side of the reference line indicates which face receives the weld; the tail carries the welding process and specification. Bolt callouts specify diameter, grade (A325 or A490 for structural), and installation method (snug-tight, pretensioned, or slip-critical). When you see a 'TC' callout, you're dealing with tension-control bolts — installation requires a TC wrench, not a standard impact gun.
The Submittal and Approval Process
Shop drawings require EOR approval before fabrication begins. The typical cycle: detailer submits → EOR reviews → EOR stamps 'Approved,' 'Approved as Noted,' or 'Revise and Resubmit' → detailer incorporates revisions → fabrication release. Only approved drawings should reach the shop floor. Keep a log of revision clouds on each sheet — they mark what changed between submission rounds and are the first place to look when a field issue arises.
Common Mistakes to Avoid
Experienced fabricators know to watch for these pitfalls:
- Using superseded revision sheets — always verify the revision triangle in the title block
- Missing cope clearances for beam-to-beam or beam-to-column connections
- Confusing similar piece marks (e.g., B101 vs. B101A) that differ only in a flange plate
- Ignoring erection sequence notes that dictate which members must be bolted before others are plumbed
- Overlooking 'hold for field measurement' callouts that mean a member cannot be cut to length until verified on site
Getting the Most from Your Detailer
A good detailing partner will catch design gaps before they become field problems. When submitting to your detailer, include the latest architectural and MEP drawings — not just structural — so penetrations, embed conflicts, and clearance issues surface in the model, not on the erection site. At Tectonix, every model goes through a dedicated QA/QC check before drawings are issued, and your U.S.-based project manager is available by phone to walk through any sheet that raises questions.