Steel shop drawings: what they are and how to review them.

What steel shop drawings are

Design drawings from the structural engineer show what the structure needs to be: member sizes, framing layout, typical connections or connection design criteria, and general notes. They aren't enough to cut and drill steel. Shop drawings translate that design into instructions a shop can execute, piece by piece.

AISC 303-22, the Code of Standard Practice, uses the term approval documents. These include fabrication (shop) drawings, erection drawings and embedment drawings, or, where the parties agree, a fabrication and erection model in place of drawings. The Code also uses ODRD, the owner's designated representative for design, which usually means the structural engineer of record.

A detailer working for the fabricator produces them, typically in 3D detailing software such as Tekla Structures or SDS2. The model generates the drawings, the bills of material, and the CNC files that drive saws, drill lines and plate processors.

Types of shop drawings

Many detailers also issue an advance bill of materials early so the fabricator can order mill material before approval. That's why late design changes can cost more than the steel itself: the material may already be ordered.

Shop drawings vs. design drawings

Design drawings say what. Shop drawings say exactly how. A design drawing may show a W16x31 with a reference to a typical shear connection. The shop drawing for that beam shows its cut length, cope dimensions, hole sizes and gauges, the connection material, weld symbols and the piece mark.

For estimators this matters because the bid is prepared from design drawings, before any shop drawings exist. Connection material, detailing hours and shop hours are estimated from typical details and connection schedules. Where those are incomplete, or connection design is delegated under AISC 303 Option 3, that's a scope risk to write into the bid. See the delegated connection design guide for how to price it.

The approval process and its timing

Under AISC 303-22, approval documents go through the approval process in Section 4.4. Unless the contract says otherwise, the Code calls for them to be returned within 14 calendar days. Project specs often set a different period in Section 01 33 00 or the steel section, so check before you build the schedule into your bid.

What approval means matters too. It indicates the fabricator has correctly interpreted the contract documents, the ODRD has reviewed and approved the connection details where required, and fabrication can proceed. It doesn't transfer responsibility for dimensions or field fit-up to the engineer.

Estimating consequences:

• Detailing schedule: your bid's schedule assumption should include detailing time, at least one review cycle and resubmittals.
• Detailing cost: most fabricators subcontract detailing and get a quote by tonnage, by piece or lump sum. Get the quote from the bid documents and adjust for complexity (skewed framing, AESS, heavy bracing).
• Revisions after approval: design changes after approval mean re-detailing, possibly scrapped material and re-fabrication. Your proposal should say these are priced as changes.

How to review steel shop drawings

Shop drawings are submitted to the GC and design team for review. A practical review, whether you're the GC, the fabricator's PM or the estimator checking your own bid, covers:

• Grids and elevations match the current structural and architectural drawings, including the latest addenda and bulletins.
• Member sizes match framing plans and schedules. Substitutions are called out and approved.
• Connections follow the design: connection types, design loads where design is delegated, bolt grades, pretensioned or slip-critical joints, weld types.
• Openings, embeds and attachments for other trades: MEP penetrations through beams, deck openings, facade attachments and elevator rail supports.
• Camber, finishes and coatings match the spec: primer type and fireproofing compatibility, galvanizing with vent and drain holes, AESS category and surface finish.
• The detailer's open questions (RFIs clouded on the drawings) are answered, not stamped through.

Where shop drawings meet estimating

After award, the shop drawing bill of materials becomes the best basis for comparing the bid takeoff with what's actually being fabricated. A practical reconciliation:

Illustrative numbers. The point is to compare by category, not in total. A total that's within 2% can hide a big miss in connections offset by a conservative member takeoff. Sheet references on every takeoff row make it possible to find the source of a difference quickly, and that feedback is what makes the next bid better.

Where RenderDraw fits

RenderDraw works on the bid side of this loop. Its AI takeoff proposes member counts, lengths and schedule data from the design drawings, with the source sheet on every row and uncertain items in a review queue. That traceability is what makes the later comparison against the shop drawing bill of materials useful.