Welding Symbols on Steel Drawings: The Complete Chart
A welding symbol is an arrow pointing at a joint, a horizontal reference line carrying the weld instructions, and optionally a tail with extra notes. The shape drawn on the reference line tells you the weld type (a right triangle means fillet, a V means V-groove), the number to its left is the weld size, and a flag at the bend means the weld happens in the field, not the shop. Symbols below the reference line apply to the arrow side of the joint; symbols above apply to the other side.
That's the whole system in three sentences. The rest of this page is the chart, the details that trip people up, and what each callout does to your labor estimate.
The Complete Welding Symbol Chart
These are the weld symbols you'll actually see on structural steel drawings, per AWS A2.4 (the standard nearly every US drawing follows). European drawings use ISO 2553, which is close enough that this chart still gets you 90% of the way.
| Symbol on reference line | Weld type | Where you'll see it |
|---|---|---|
| Right triangle (▷) | Fillet weld | Everywhere — clip angles, shear tabs, stiffeners. 80%+ of structural welds |
| V shape | V-groove weld | Butt joints, splices, moment connections |
| Half-V (one vertical leg, one angled) | Bevel groove weld | Tee joints where only one plate is prepped |
| Two parallel vertical lines (‖) | Square groove weld | Thin material butt joints, minimal prep |
| U shape | U-groove weld | Thick material splices (rare on typical jobs) |
| J shape | J-groove weld | Thick tee joints (rare) |
| Flat-bottomed V with curved sides | Flare-V / flare-bevel | Welding to rounded surfaces — HSS corners, rebar |
| Circle at the arrow bend | Weld all around | Base plates, HSS-to-plate, closure welds |
| Filled flag at the arrow bend | Field weld | Any weld made at the site instead of the shop |
| Filled circle | Plug/slot weld | Doubler plates, built-up members |
| Curved cap over the weld symbol | Contour (flush/convex) | Finish requirement — grind flush, etc. |
Supplementary data that rides along on the reference line:
| Element | Position | Meaning | Example |
|---|---|---|---|
| Size | Left of the weld symbol | Fillet leg size or groove depth | 1/4 ▷ = 1/4" fillet |
| Length | Right of the weld symbol | Length of the weld | ▷ 6 = 6" long |
| Length–pitch | Right, as L–P | Intermittent weld: length, then center-to-center spacing | ▷ 2–6 = 2" welds every 6" |
| Tail note | Fork at the end of the reference line | Process, spec, or "TYP" | ▷ ← TYP |
Print this section. It covers almost every callout on a typical fabrication package. For the abbreviations that show up next to these symbols (CJP, PJP, TYP, N.S., F.S.), see the steel abbreviations and drawing symbols chart.
How Do You Read the Welding Symbol Structure?
Every welding symbol has three possible parts, read in this order:
- The arrow points at the joint. Not at a member — at the specific joint line where metal meets metal.
- The reference line is the horizontal line the arrow hangs off. All the actual instructions live here.
- The tail (an open fork at the far end) is optional. It carries notes: the welding process (SMAW, FCAW), a spec reference, or "TYP."
The rule that causes the most re-reads: arrow side vs. other side.
- Weld symbol below the reference line → weld goes on the arrow side of the joint (the side the arrow physically touches).
- Weld symbol above the reference line → weld goes on the opposite side.
- Symbols on both sides of the line → weld both sides. A triangle above and below is the classic double-fillet callout on a tee joint — and it doubles your weld inches, so don't miss it.
Note the reference is the joint, not up/down in space. An arrow pointing down at the underside of a beam flange with the triangle below the line still means "weld the side the arrow touches."
One more convention: multiple arrows can branch off one reference line. One symbol, three arrows = same weld at three joints. Count all of them.
What Does the Fillet Weld Symbol Mean and How Is Size Shown?
The right triangle is the fillet weld — a triangular bead laid into the corner where two pieces meet at (roughly) 90°. It's the workhorse of structural steel because it needs no joint prep: no beveling, no back-gouging, just fit and weld.
The number to the left of the triangle is the leg size in inches — the length of each leg of the triangular cross-section, not the throat.
| Callout | Meaning |
|---|---|
| 3/16 ▷ | 3/16" fillet, continuous, one side |
| 1/4 ▷ (both sides of line) | 1/4" fillet both sides of the joint |
| 5/16 ▷ 8 | 5/16" fillet, 8" long |
| ▷ with no size | Size per general notes or minimum per AWS D1.1 — check the general notes sheet before assuming |
Rules of thumb that matter for pricing:
- Weld volume scales with the square of the leg size. A 1/2" fillet takes roughly 4x the filler metal and arc time of a 1/4" fillet, not 2x. A drawing that bumps fillets from 1/4" to 3/8" raised your weld labor ~125%, not 50%.
- 3/16" and 1/4" are the bread-and-butter sizes for shear connections on typical W-shapes. Anything 3/8" and up deserves a second look — heavy framing or a conservative drafter, and either way it's labor.
- If no size is shown anywhere, AWS D1.1 minimum fillet sizes apply based on the thicker part joined.
What Is the Flag on a Weld Symbol?
The filled black flag at the bend where the arrow meets the reference line is the field weld symbol. It means this weld is made at the job site during erection, not in the fabrication shop.
This one symbol changes who does the work, when, and at what cost:
- Shop welds happen flat or horizontal on fixtures, with FCAW or SAW, at shop labor rates.
- Field welds happen off a lift, often out of position, by an ironworker crew at field rates. Most estimators carry field weld inches at 2x to 4x the same weld inch in the shop, plus weather and access risk.
Bidding fab-only with the flags belonging to the erector? You still care — every field-welded connection means erection aids, run-off tabs, or backing bars on your side. Bidding fab + erect, missed flags are a classic way a steel bid loses money. The shop-vs-field split is a big part of why bolted connections usually beat welded on installed cost: a field bolt is minutes, a field weld is an hour with a qualified welder and possibly an inspector watching.
Groove Weld Symbols: V, Bevel, Square, U, J
Groove (butt) welds join pieces edge-to-edge or tee into each other with prepped edges. The symbol shape mirrors the prep shape:
| Symbol | Weld | Prep | Typical use |
|---|---|---|---|
| V | V-groove | Both edges beveled | Column splices, flange welds in moment frames |
| Half-V | Bevel groove | One edge beveled, one square | Tee joints, one-sided access |
| ‖ | Square groove | No bevel, just a gap | Material under ~1/4" |
| U | U-groove | Both edges gouged to a U | Very thick splices; less filler than a V |
| J | J-groove | One edge gouged to a J | Thick tee joints |
| Flare-V / flare-bevel | Flare groove | None — the curve of the member is the groove | HSS face welds, round bar |
The two abbreviations that ride with groove symbols, usually in the tail:
- CJP — complete joint penetration. Weld fuses the full thickness. Requires certified welders, often UT inspection, and real prep time. A CJP flange weld on a moment connection can run into hours per joint.
- PJP — partial joint penetration. The number in parentheses on the symbol, e.g. (1/2), is the required effective throat; the unparenthesized number left of the symbol is the prep depth.
For an estimate: a CJP groove weld is routinely 5-10x the labor of a fillet on the same joint once you count prep, preheat on thick material, back-gouging, and NDE. When a job's connection sheets are full of CJP callouts — typical of moment frames — weld labor can rival the material cost. That's a fundamentally different bid than a shear-tab job, which is why it pays to know your steel connection types before you price the welding.
Weld-All-Around, Typical Notes, and Intermittent Welds
Three callouts that quietly multiply weld inches:
Weld all around — an open circle at the arrow bend. The weld runs the entire perimeter of the joint. On an HSS6X6 to a base plate, ▷ with a circle isn't "some weld" — it's 24 inches of fillet. Perimeter = weld length. Do the math on every one.
TYP (typical) — usually in the tail or beside the symbol. The callout applies to all similar joints on the detail, sometimes the whole job. "1/4 ▷ TYP" on a stiffener detail with 40 stiffeners is 40 welded joints from one symbol. "Typical" is where most missed weld quantities hide — the symbol appears once, the work appears everywhere. Same trap as "do." marks and "similar" details, covered in how to read structural drawings.
Intermittent welds — length–pitch to the right of the symbol: ▷ 2–6 means 2" welds on 6" centers, so actual weld inches are 1/3 of the joint length. Staggered intermittent fillets show offset triangles above and below the line — both sides, alternating. Common on built-up members and long stiffeners, and good news for the estimate: a third of the weld metal of a continuous callout.
What Do Welds Mean for Your Estimate: Shop vs Field Labor
A takeoff that counts members but ignores weld symbols prices the steel and misses the labor. The working hierarchy, cheapest to most expensive per connection:
| Callout | Relative labor | Watch for |
|---|---|---|
| Small fillet (3/16"–1/4"), shop | Baseline | Length and "both sides" |
| Fillet 3/8"+ or all-around, shop | 2-4x | Volume scales with size² |
| PJP groove, shop | 3-6x | Prep + effective throat |
| CJP groove, shop | 5-10x | Certified welders, UT/NDE |
| Any of the above with a flag | 2-4x again | Field rates, access, weather |
Practical workflow: take off the members first, then run the connection details and count welded joints by type — continuous fillet inches, intermittent inches, groove welds by count, and field welds as their own bucket. Tools help with the first pass: SteelFlo's AI detection finds and boxes every steel member label across a drawing set with 95-99% accuracy when paired with your human review, which clears the counting work off your desk so your estimating hours go into the connection details and weld callouts, where the judgment (and the margin) actually lives.
FAQ Quick Answers
What does the triangle mean on a weld symbol? A fillet weld. The number to its left is the leg size in inches.
What does the flag mean? Field weld — made at the site during erection, not in the shop. Price it at field labor rates, typically 2-4x shop.
What does the circle at the bend mean? Weld all around — the weld runs the full perimeter of the joint.
Which side of the reference line is the arrow side? Below the line = arrow side. Above the line = other side. Both = weld both sides.
What's the difference between CJP and PJP? CJP fuses the full joint thickness (most labor, usually inspected). PJP fuses to a specified effective throat shown in parentheses.
Counting members shouldn't eat the hours you need for weld and connection analysis. SteelFlo reads your PDF drawing set, finds every steel member label across 4,500+ sections and 6 international standards, and hands you a reviewable takeoff — so you spend your time on the callouts that decide whether the bid makes money. Start 3 free takeoffs — no card required.