Steel Shop Drawings Explained: What a Complete Package Contains

A steel shop drawing is a fabrication drawing that tells the shop exactly how to make a piece: its material, cut lengths, holes, copes, welds, finish and the parts that attach to it. Shop drawings are prepared from the contract design documents, reviewed and approved by the design team, and used on the shop floor.

Under AISC 303, the Code of Standard Practice, the fabricator is responsible for shop and erection drawings, whether its own detailers prepare them or an outside detailer does. Design drawings show what the structure must be; shop drawings show how each piece of it gets built.

A complete package includes a drawing index, general notes, anchor rod setting plans where they are in scope, erection plans, elevations and sections, assembly details, part details, bills of material, shop and field bolt lists, material takeoffs, NC files and a transmittal with a revision log. Each missing item should be a deliberate scope decision.

General notes state the rules that apply to every sheet so they do not have to be repeated on each detail: material specifications for each type of steel, bolt specifications and joint type, standard hole sizes, welding electrodes and the welding code, surface preparation and coating, the standards the drawings follow, and the abbreviations and symbols used.

A real example of the level of specificity involved, from a package detailed by Vertex for an airport terminal rehabilitation and addition in New England:

• A992 W shapes; A36 plate and angle; A500 Grade B tube; A53 pipe
• A325N bolts, snug-tightened, in 13/16" holes
• E70XX electrodes
• SSPC-SP2 cleaning and shop primer at 1.5 mils DFT

When a general note conflicts with a specification section, the conflict belongs in an RFI, not in a quiet choice on the drawing.

An assembly detail shows a shipping piece: the main member plus every plate, angle and clip welded or bolted to it in the shop, carrying a ship mark. A part detail shows one piece, such as a plate or angle, carrying a minor mark. Assembly details guide fitters and welders; part details guide cutting and drilling.

Keeping the two consistent is where many errors hide: a plate revised on its part detail but not on the assembly that uses it produces a piece that cannot be fitted.

A bill of material lists everything needed to make the pieces on a sheet: each mark, its quantity, its description or size, its length, its material grade, and its weight, often with finish or remarks. It is how the shop buys, cuts, counts and ships material, so it must agree exactly with the details it sits beside.

On the frame detail sheets of the New England airport terminal package, the bills of material carried ship marks, minor marks, quantities, lengths, grades and unit weights, and field bolts were kept on a separate field bolt list. The case study describes that package.

Erection drawings show where each shipping piece goes in the structure; shop drawings show how each shipping piece is made. The ship mark links them: the mark on the erection plan is the mark on the assembly detail and the mark on the piece arriving at site. Field connections and field bolt lists live on the erection side.

If marks disagree between the two sets, the field crew finds a piece it cannot place. That is why erection drawings, shop drawings and bills of material should come from the same model and be checked against each other. See erection drawings for what each erection sheet contains.

Revisions are shown with a cloud around each change, an entry in the sheet's revision block, and an advanced revision letter or number. A common convention is letters for issues for approval, such as Rev A, and numbers for issues for fabrication, such as Rev 0, so anyone can tell whether a sheet is cleared to build.

When a sheet is revised, the bills of material, bolt lists and NC files that belong to it must be reissued with it, and superseded copies withdrawn from the shop floor. A beam line cutting from an old NC file while the fitters read a new drawing is one of the most expensive ways a revision can go wrong.

Review a shop drawing package in layers: first confirm it is complete and current, then that it matches the design, then that it agrees with itself. Start with the drawing index and general notes, check member sizes, grades and connections against the design drawings, and then confirm that marks, quantities and revisions line up across erection drawings, details and lists.

• The drawing index lists every sheet at its current revision
• General notes match the specifications for materials, bolts, welds and finish
• Member sizes and grades match the design drawings
• Connections match the Engineer of Record's details or delegated design
• Bolt diameters, grades, lengths and hole sizes are called out
• Weld symbols are complete, with size, type and length
• Ship marks agree across erection drawings, assembly details and bills of material
• Finish is stated for every piece, especially on mixed galvanized and painted jobs
• Pieces affected by open RFIs are flagged, not silently detailed
• Every change since the last issue is clouded

The most common deficiencies are inconsistencies rather than exotic errors: marks that do not match between sheets, bills of material that disagree with the details, missing weld symbols, hole call-outs left off, finishes omitted, revisions that were changed but not clouded, and NC files or bolt lists issued from an older revision than the drawings.

Those errors are cheap on paper and expensive in the shop or field. A second person checking every sheet against the design documents and against the other sheets, then back-checking corrections, is what keeps them off the shop floor; Vertex describes its sequence on the quality control page. How AISC standards shape the notes and details is covered in AISC standards for steel detailing, and what Vertex delivers is on steel shop drawings.