Structural steel drawings are dense, symbol-heavy, and easy to misread if you don’t know what you’re looking at. Misreadings and incomplete packages can significantly affect the project timeline, leading to rounds of rework and delays that push completion back.
Learn the structural steel drawing types, weld symbols, and everything that goes into a complete drawing package, so you’ll have confidence to communicate clearly with a fabricator and get the outcome you need.
The 3 Types of Drawings in a Structural Steel Set
Before you get into the weeds of structural drawing components, you need to first understand the three main drawing types. Confusing one for the other is a common mistake when you don’t understand the purpose of each type. The drawing types below each follow a predictable structure, so once you know how to spot each one, you’ll be able to do so consistently.
1. General Arrangement (GA) Drawings
General arrangement (GA) drawings show the big-picture view of the fabrication project. Think of them like a map. GA drawings help you understand the scope and spatial relationships of each structural member.
These drawings, often built from 3D CAD design files, include column grid positions, beam spans, primary member sizes, and floor/roof framing. Identify a GA drawing by the intersection references, like “beam at C-3,” which establish relationships between members. A GA drawing won’t include details and fabrication specifics, such as bolt hole patterns or weld callouts.
2. Shop and Assembly Drawings
Shop drawings, also known as assembly or fabrication drawings, provide a more detailed view of individual members within an assembly. They’ll include exact dimensions, material grade, hole locations, weld callouts, and piece marks.
The fabricator looks for and works from this type of drawing. As a project manager, your job will be to verify that all details, like fabrication tolerances, are clear and present in the shop drawing. Discrepancies at this step will likely lead to costly shop errors.
3. Erection Drawings
Erection drawings, also called marking plans, are the drawings that the field crew relies on to understand where and how each finished piece fits into the assembly of the completed project. This type of drawing references the piece marks from the shop drawings and indicates bolt quantities, connection types, and field weld locations.
What’s important for the project manager is to check the erection drawings for correct grid references and elevation marks that match the GA drawing.
How to Read Weld Symbols on Structural Steel Drawings
Weld symbols on drawings follow the AWS A2.4 standard, which means that the horizontal reference line, arrow, and symbol placements above or below the line communicate type, size, location, and whether the weld happens in the shop or in the field.
These symbols are important to understand, as misreading a weld callout means you’ll send the wrong instructions to the fabricator, resulting in the need for rework. We’ll cover the need-to-know symbols for project managers, but there are resources to help those who want to know more understand the full weld symbol chart.
Reference Line and Symbols
Here are the basic elements you’ll want to reference and understand when looking at a structural steel drawing:
- Reference line: The horizontal line that anchors every welding symbol. Every other element attaches to it.
- Arrow: Connects the reference line to the joint.
- Arrow-side and other-side: The side of the joint where the arrow points to is the arrow-side. The opposite side is called the other-side.
- Weld symbol: The graphic character that specifies the weld type. It can be positioned on the arrow side or the other side, to indicate where to weld.
- Size and length: The size is shown on the LEFT of the weld symbol, and the length (length-pitch) is written to the RIGHT of the weld symbol.
For example, if you have a horizontal reference line with an arrow pointing below it and a triangle symbol below the line, it indicates that a fillet weld is required on the arrow side.
Field Welds vs. Shop Welds
Another important symbol to look out for is the field weld symbol. It’s a solid triangular flag placed at the junction of the reference line and the arrow. It indicates that the weld is intended to be made in the field (at the erection site) rather than in the fabrication shop.
What’s in a Structural Steel Shop Drawing Package?
Submitting a complete drawing package is one of the highest-leverage tasks you can do as a project manager. NISD standards confirm that complete structural design documents must clearly show the work to be performed and include the size, section, structural steel grade, and location of all members.
Below is a checklist of elements to include in your package before handing it off:
- Finalized GA drawings.
- Material grades and member sizes.
- Weld specifications, per AWS.
- Bolt details.
- Tolerances.
- Assembly/erection references.
- Finish or coating requirements.
While it’s important to make sure you have all the information you need before handing off, a good metal fabricator will likely flag any gaps in your package before they start cutting.
A Reading Sequence for Project Managers
Ready to start applying your newfound knowledge? Here’s a practical step-by-step approach to reading your next structural steel drawing and interpreting it for handoff:
- Read the title block: Check the sheet number, revision, and date.
- Pull up the GA drawing: Walk the grid to understand the building’s layout.
- Identify primary members: Note the main member types and sizes on the GA.
- Move to the shop drawings: Match piece marks to the GA. This is the single most important cross-check. The piece mark on the GA, the shop drawing, and the fabricated piece must all match.
- Check weld callouts: Flag any field welds (indicated by a flag symbol) for scheduling.
- Review the full package: Check for completeness before submitting to the fabricator.
The goal of this walk-through, as a project manager, is not to become an expert engineer but to be knowledgeable enough to communicate effectively with your team. You want to be able to work with a trusted steel fabrication partner who can build from your package without any guesswork.
Work With Mid-Atlantic Steel Fabrication on Your Next Project
When you understand the basics of a structural steel drawing set, rework and miscommunication are no longer the norm – they become the exception.
If you’re looking to turn your drawing package into a completed assembly without second-guessing every callout, Mid-Atlantic Steel Fabrication is your trusted partner for premium metal fabrication services. Work with our team of D1.1 structurally certified fabricators to bring your steel project ideas to life.
Call us at 717-687-7313 or request a free quote today!