AutoCAD for Steel Fabrication: Structural Detailing and Shop Drawings

Shop drawings are the bridge between an engineer’s design and the fabricator’s workshop floor. Where structural engineering drawings show what is to be built — member sizes, load paths, connection types — shop drawings show how to build it: exact dimensions of each member, hole patterns, weld specifications, surface treatments, and assembly sequences. These are the drawings that go to the cutting machine, the welding jig, and the site installation team.

AutoCAD has been a staple tool for steel fabrication drawings for decades. While specialist software like Tekla Structures or Advance Steel (an AutoCAD-based product) automates much of the process for large structural projects, standalone AutoCAD remains highly relevant for smaller fabricators, one-off details, and drawings that need to integrate with a broader CAD environment.

This guide covers how to produce professional steel fabrication shop drawings in AutoCAD: setting up drawing standards, drawing sections and details, annotating weld specifications, creating bill of materials, and structuring a drawing package that a fabrication shop can use directly.

The full AutoCAD product is required for the workflows in this guide. AutoCAD 2023–2026 is available from GetRenewedTech for £39.99.

Drawing Standards for Steel Fabrication

Steel fabrication drawings follow established conventions. In the UK, the primary standards are:

• BS 8888:2017 — Technical product documentation and specification. Covers drawing layout, line types, symbols, and annotation conventions.
• BS EN ISO 2553 — Welding symbols on drawings. Defines the standard way to annotate welds including process, method, dimensions, and position.
• BS EN 22553 / ISO 1101 — Geometrical dimensioning and tolerancing (GD&T).
• SCI P358 — Joints in Steel Construction: Simple Joints. Provides standard connection details referenced in many UK structural drawings.

Before starting, configure AutoCAD to reflect these standards in your template:

Line Types and Weights for Steel Drawings

• Visible outlines: Continuous, 0.50mm — main object outlines, cut surfaces, section faces
• Hidden lines: Dashed (HIDDEN2), 0.35mm — edges hidden behind the viewing plane
• Centre lines: Centre (CENTER2), 0.25mm — hole centres, part centroids, axes of symmetry
• Dimension lines: Continuous, 0.18mm — dimension lines and leaders
• Section cut plane: Section (chain dash with arrows), 0.70mm — indicates where sections are cut
• Break lines: Zigzag or wavy, 0.25mm — shows that a drawing is interrupted (long members shortened for drawing purposes)

Layers

Drawing Standard Sections

Steel members are typically drawn using standard section profiles: universal beams (UB), universal columns (UC), hollow sections (RHS, SHS, CHS), angles (L), channels (C), and flat bar. Rather than redrawing these each time, build a block library of standard section profiles at accurate dimensions.

Creating a UB Section Block

Universal Beam dimensions are defined by the Blue Book (SCI publication P363) and the equivalent European standard EN 10034. For a 254×146 UB 43 kg/m section:

• Overall depth (d): 259.6mm
• Flange width (b): 147.3mm
• Web thickness (tw): 7.2mm
• Flange thickness (tf): 12.7mm
• Root radius (r): 7.6mm

Draw the section cross-section using LINE and ARC commands at these exact dimensions, or use PLINE for a single object. Create it as a BLOCK named UB254x146x43 with the insertion point at the centroid. For common sections you use regularly, create an entire library — this initial investment saves significant time across multiple projects.

Alternatively, download steel section DWG blocks from SteelConstruction.info or the CADS RC section library — these are freely available and cover the full Blue Book section range.

Drawing Member Elevations and Plans

A typical shop drawing package includes:

1. Member elevation: The primary view showing the full length of the member, connection ends, and main dimensions
2. End views/sections: Cross-section views at each connection point or significant change in geometry
3. Connection details: Larger-scale views of complex bolted or welded connections
4. Bill of Materials: Table listing every component piece with its mark, quantity, specification, and dimensions

Bolt Hole Patterns

Bolt hole positions must be dimensioned precisely — errors here result in holes that do not align during site assembly. Recommended approach:

1. Use the SNAP and GRID settings to work to a bolt pitch grid (typically 70-90mm for M20 bolts in standard fin plate connections).
2. Draw holes as circles (radius = hole diameter / 2; for M20 bolts in standard clearance holes: 22mm diameter hole).
3. Mark hole centres with a cross-hair centre mark (use the DIMCENTER command or draw a small cross pattern).
4. Dimension the edge distance to the first hole, then the pitch between holes, following BS 5950/BS EN 1993-1-8 minimum and maximum edge distance requirements.

Standard UK steel design minimum dimensions for M20 bolts (from BS EN 1993-1-8):

• Minimum edge distance: 1.2d₀ = 26.4mm (typically specified as 35mm)
• Maximum edge distance: 4t + 40mm where t = plate thickness
• Minimum pitch: 2.2d₀ = 48.4mm (typically specified as 70mm)

Welding Symbols

Welding symbols on fabrication drawings follow BS EN ISO 2553. The symbol consists of:

• A reference line (horizontal dashed line)
• An arrow pointing to the weld joint
• The weld symbol above or below the reference line (above = other side; below = arrow side)
• Weld dimensions (size of weld leg or throat thickness)
• Supplementary symbols (full penetration, backing strip, etc.)

Common weld symbols you need as blocks:

• Fillet weld: Right-angled triangle symbol. Size (leg length) shown to the left: 5⊿ = 5mm fillet weld
• Butt weld (V-groove): V-shape symbol. May include penetration depth and opening angle
• Partial penetration butt weld: Similar to butt weld with depth specification
• All-around weld: Circle at the junction of arrow and reference line, indicating weld goes all the way round
• Stitch weld: Fillet weld symbol with length and pitch notation: 5⊿ 50-150 = 5mm fillet, 50mm length at 150mm centres

Create each weld symbol type as an attributed block with fields for weld size, method (manual arc, MIG, TIG, submerged arc), and notes. This allows them to be inserted consistently and extracted into a welding schedule if needed.

Surface Treatment Annotations

Shop drawings must specify the surface treatment to be applied before delivery to site. Common UK specifications:

• Shot blasting grade: Sa 2.5 (near white metal blast clean) — the standard pre-treatment for protective coatings, defined in BS EN ISO 8501-1
• Primer type: Zinc-rich epoxy or zinc phosphate primer, 75µm DFT (dry film thickness)
• Top coat: Where required, specified by the structural engineer as part of the corrosion protection specification
• Galvanising: Hot-dip galvanising to BS EN ISO 1461 for corrosive environments

Surface treatment notes typically appear in the general notes section of the drawing or title block rather than as per-weld symbols. Include a standard note block in your template.

Creating a Bill of Materials (BOM)

The Bill of Materials lists every component piece in the assembly. For steel drawings, each entry includes:

• Piece mark: A unique identifier (e.g., C1, P2, G3) that appears as a balloon callout on the drawing and on physical marking of fabricated pieces
• Quantity: Number of pieces
• Description: Section reference (e.g., 254×146 UB 43 kg/m) or flat plate specification (e.g., PL15)
• Material grade: S275 or S355 (structural steel grades per BS EN 10025)
• Length: Finished length of the member
• Mass: Per piece and total (section mass per metre × length)

Using AutoCAD Tables and Data Extraction for BOM

Create the BOM as an AutoCAD table (TABLE command) with the appropriate columns. For live extraction, use attributed blocks for each piece mark callout balloon and extract the attributes using Data Extraction (DATAEXTRACTION) as described in the landscape design article — the same technique applies here. The BOM table can then update automatically as piece marks are added or quantities change.

For a typical single-member shop drawing, a manually maintained table is often faster than setting up extraction. For complex assemblies with 50+ pieces, the extraction approach pays for itself quickly.

Drawing Scale and Dimensioning

Steel shop drawings are typically produced at 1:20 or 1:10 for main views, with connection details at 1:5 or 1:2 if needed. Member elevations of long spanning members may be drawn at 1:50 with break lines indicating shortened representation.

Dimensioning Steel Drawings

Dimensions on steel shop drawings should be:

• Chain dimensioned (running from a datum) rather than overall-only dimensions — this avoids accumulation of tolerances
• Given as finished dimensions (after cutting, drilling, and preparation)
• Referenced to connection centre lines and bolt hole centres rather than to edges where possible
• Toleranced where fabrication tolerance is critical (e.g., ±1.0mm on bolt hole centres)

Use the Architectural dimension style as a starting point and modify it: set units to Decimal, precision to 0 (whole mm), dimension text above the line (British Standard convention), and arrows to closed filled at an appropriate size for your drawing scale.

Title Block and Drawing Management

A steel fabrication drawing title block should include:

• Company name and logo
• Project name and contract number
• Drawing title and drawing number
• Scale(s) used
• Material specification (S275/S355)
• Surface treatment specification
• Design standard reference (BS EN 1993)
• Drawn by, checked by, approved by
• Issue date and revision table
• Folding marks (for A0/A1 drawings being folded to A4)

Create this as a block with attributes for all variable fields. Store it in your template at the correct position on the drawing sheet.

Revision Management

Shop drawings are regularly revised — connections change, section sizes are modified, the engineer issues a revision. Managing revisions clearly is critical to avoid fabricating to superseded information.

Best practice:

• Cloud mark changes on the revised drawing (draw a cloud shape around changed areas using REVCLOUD)
• Add a revision entry to the title block revision table with revision letter, date, description of change, and the initials of who made the change
• Issue revisions as PDF with a clear revision designation in the filename: B04-BEAM-DETAIL-REV-C.pdf
• Ensure the previous revision is clearly marked as superseded

Conclusion

Producing high-quality steel fabrication shop drawings in AutoCAD requires disciplined layer management, a good block library of section profiles and weld symbols, and adherence to BS EN drawing standards. The investment in a well-configured template and block library is paid back across every drawing package produced.

For very large structural packages with hundreds of members, specialist tools like Advance Steel (built on AutoCAD) or Tekla Structures automate much of the detailing process. But for standard fabrication drawing work — bespoke connections, individual member details, sub-assembly drawings — AutoCAD’s precision, layer control, and flexibility make it an entirely appropriate tool.

Get started with AutoCAD 2023–2026 from GetRenewedTech for £39.99.