Why You Keep Misreading Steel Shop Drawings
You open a PDF from the fabricator and immediately hit a wall of shorthand. WELT. GUS. SP. These aren't arbitrary. They're standardized abbreviations that save space on drawings where every square inch matters. I've spent years going back and forth between site teams and detailers, and the single biggest source of RFI's I see isn't geometry errors or connection misunderstandings. It's simple misreading of abbreviated callouts. A WELT vs a GUS plate can mean the difference between a proper stiffener and a complete rework on a beam web. The problem most people face is that abbreviation usage varies slightly between offices and regions. ASTM A6 and AISC 360 don't actually standardize drawing abbreviations - that falls under AISC Code of Standard Practice. The American Institute of Steel Construction publishes references, but individual detailers have their own habits. Some will write CONT WELT all around, others will use a symbol. This inconsistency is what drives people to keep reference guides open on their second monitor.
Common Abbreviations You'll Actually See on Drawings
PL - Plate. Nothing surprising here, but watch for it combined with dimensions like PL 1/2" x 6" x 0'-6" which means a half-inch thick plate, six inches wide, six feet long. The order matters. Width comes before length in standard plate notation. Get that backwards and you cut the wrong material. WT - Wide flange cut lengthwise. This is a split shape. A WT6x20 is literally a W12x40 cut in half through the web. Detailers use these when they need a T-shape without ordering a special mill product. If you see WT on a connection drawing, assume the parent shape dimensions are available in the general notes or the member schedule. ST - Section. Usually refers to a standard rolled section when the full designation isn't repeated. A callout like "ST 9x12" means a stud section, not a standard I-beam. Don't confuse ST with S-shapes. S4x7.5 and ST4x7.5 are completely different things. One is a structural splaying, the other is a cold-formed stud. The weight difference alone changes your connection design.
GUS - Gusset plate. triangular or irregular shaped plate used at connections. On drawings, you'll often see "GUS PL 3/8 x 10 x 8" which tells you thickness, width, and length. The shape itself is usually shown graphically. Don't try to reconstruct gusset geometry from text alone. WELT - Wait for field. Sometimes written as W.F. or just a note pointing to a connection that gets completed on site rather than in the shop. This one causes more problems than any abbreviation I've seen because field conditions vary wildly. A bolt pattern that fits in the shop might not align once the column settles during erection. Always confirm wait-for-field items with the erector before proceeding. SP - Split point or splice location. Often appears on long beams or columns where the member runs too far for a single piece. Splice details show you how the connection works, but pay attention to whether the splice is at a panel point or mid-span. A mid-span splice requires different considerations than one located at a support.
Get the Full Details
Structural Steel Drawings Abbreviations Guide
B - Bottom. As in B.F. for bottom flange. Don't overthink this one. T - Top. Paired with B for flange references. SIDE - Side. Often used in elevation views to indicate which side of a member an item is located on.
EOC - Edge of connection or sometimes end of column depending on context. This abbreviation changes meaning based on drawing type. In plan views it usually means edge of connection. In elevation it could mean end of column. Context is everything. OC - On center. Standard spacing reference. You'll see this constantly in bracing layouts and decking patterns. GAGE - The distance from the outer face of the flange to the first row of bolt holes. Different shapes have different standard gages. W8x31 has a gage of 5.5 inches. W12x50 has a gage of 5.5 inches too. But W18x50 jumps to 7.5 inches. If your connection drawing shows bolt holes but no gage dimension, it's because the gage is standard for that shape. You can find it in the AISC Manual Table 1-1.
THRU - Through. As in bolt thru hole or weld thru. Means something passes completely through the member. CONT - Continuous. Continuous weld or continuous bearing. Context determines which. LEG - Leg of a fillet weld. A 3/8" LEG fillet weld means each leg of the triangular weld cross-section is three eighths inch. Total throat would be approximately 5/16". Detailers don't always call out throat because it's a straightforward calculation from leg size.
CANT - Cantilever. Self explanatory but often attached to span lengths like CANT 8'-0".
What Nobody Tells You About Reading These Abbreviations
The real issue isn't memorizing what each abbreviation means. Any competent detailer or fabricator has a reference sheet at their desk. The actual problem is that abbreviations appear in combination, and the combination can change meaning entirely. Take something like "PL 1/2" x 6" x 0'-6" WELT 6 EA @ 2'-0" OC." That's a half-inch by six-inch by six-foot plate, wait for field, six each spaced at two feet on center. Read it wrong and you might think the plate length is six inches instead of six feet. The space between dimensions and the abbreviation is where people slip up. Another thing detailers don't always make clear: abbreviation density changes between shop drawings and construction drawings. Shop drawings are heavier on abbreviations because they're intended for the fabricator who already knows the language. Construction drawings meant for the engineer of record tend to spell things out more. If you're reviewing shop drawings as an inspector or project engineer, don't assume the abbreviations are lazy writing. They're deliberate efficiency. The drawings would be twice as cluttered without them. I ran into a situation last year on a warehouse project where the steel detailer used "ST" to mean "staggered" rather than "stud section." The connection detail showed bolt patterns with staggered rows, but the note simply said "ST 3" VxH." Anyone reading that as a structural stud section would have been completely confused. I caught it by cross-referencing the bolt pattern drawing, where the stagger was clearly visible. That's the kind of thing that takes years of exposure to recognize. There's no shortcut around it except looking at the overall drawing set and seeing how the abbreviation is used in context.
The AISC Manual's Appendix on abbreviations and symbols is useful but incomplete. It covers the basics and some common ones, but it won't help you with office-specific shorthand. Some larger detailing firms maintain internal standards that go well beyond what AISC documents. If you work regularly with the same fabricator, ask for their abbreviation key. Most will provide one if you ask politely. It saves you from guessing what their version of "PNL" means versus someone else's.
Where the Guide Falls Short
No abbreviation guide covers everything. The industry doesn't have a single authoritative list that every detailer follows. Different software packages default to different abbreviations. Tekla Structures might generate one set of shorthand while SDS2 produces another. Even within the same firm, different detailers may have different personal preferences that crept in over decades of practice. You will encounter abbreviations that don't appear in any published guide. The biggest limitation is that abbreviation meaning can shift between disciplines. A structural engineer, an architect, and an MEP coordinator might all be using the same abbreviation with slightly different meanings. "MOL" could mean centerline of member in one set of drawings and minimum overlap in another. Always check the drawing title block or general notes for a legend. If there's no legend, assume the abbreviation follows AISC convention and verify with the detailer before acting on it. Electronic drawing review platforms sometimes interpret abbreviations differently than paper. When you zoom into a connection detail on a tablet, text rendering can make certain abbreviations look like something they're not. "GUS" can look like "GUS" with a stray speck that makes it read as "GUS." It sounds ridiculous until you've spent twenty minutes trying to figure out what a "GUS" plate actually is before realizing the "S" was a printing artifact. Always verify ambiguous abbreviations by checking the surrounding context or asking the detailer directly.
If you're starting out and feeling overwhelmed by the shorthand, the practical approach is to carry a small reference card or bookmark the AISC abbreviation tables and keep them open while you work through a full drawing set. Don't try to memorize everything. Build your familiarity by encountering the same abbreviations repeatedly across multiple projects. Within three or four jobs, you'll recognize most of them without looking anything up. The ones you don't recognize will tell you something about the detailer's office habits, which is useful information in itself.
