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AWS A2.4 §6.3, §7.3 · D1.1:2025 Figure 5.1

J-Groove Weld Symbol

How to read a J-groove weld symbol — perpendicular leg left, J-curve right, root radius in the detail only. Broken arrow convention, and D1.1:2025 prequalified CJP joint details.

J-Groove Weld Symbol — Anatomy
45° 3/4 perp leg LEFT, J right
Single-J — 45°, D=3/4"
broken arrow = prep THIS member
Broken arrow convention
prep from both sides
Double-J groove
Key rule: Per A2.4 §7.3.3, root radius (r) and root face (f) cannot appear on the symbol line. They must be in a referenced cross-section detail. This is unique to J-groove and U-groove welds.
How to Read

J-Groove Symbol Dimensions

The J-groove symbol has a vertical line (perpendicular leg) on the LEFT and a J-curve on the RIGHT. Per A2.4 §6.3, the perpendicular leg is always on the left regardless of which side of the reference line the symbol sits on.

What Goes on the Symbol

Root opening (R) — INSIDE the symbol.

Groove angle (α) — to the RIGHT.

Groove depth (D) — to the LEFT for PJP.

Weld size (S) — in parentheses to the LEFT for PJP.

What Does NOT Go on the Symbol

Root radius (r) and root face (f) — per A2.4 §7.3.3, these MUST appear in a referenced cross-section detail or note. Not on the symbol line. This is a common drafting error.

Broken Arrow

Like the bevel groove, the J-groove prepares only one member. The broken arrow points to the member that receives the J-preparation. A straight arrow means the fabricator may choose which member to prepare.

Perpendicular leg rule: The vertical line is always on the LEFT of the symbol shape. This applies to J-groove, bevel, and all asymmetric groove welds per A2.4 §6.3.
D1.1:2025 Figure 5.1

Prequalified J-Groove CJP Joints

D1.1:2025 Figure 5.1 Type 8 (single-J) and Type 9 (double-J) specify prequalified CJP joint details. All prequalified J-groove CJP joints require backgouge.

Parameter SMAW GMAW / FCAW
Joint designation B-U8 B-U8-GF
Groove angle (α) 45° all positions 30° all positions
Root face (f) 1/8" (3mm) 1/8" (3mm)
Root radius (r) 3/8" (10mm) 3/8" (10mm)
Root opening (R) 0–1/8" (0–3mm) 0–1/8" (0–3mm)
Backgouge Required Required
Economy note: J-groove preparation reduces weld metal volume compared to V-groove on thick plate. For material >1", the savings in filler metal, heat input, and distortion justify the higher preparation cost.
Common Questions

J-Groove Weld Symbol FAQ

What is the difference between a J-groove and a bevel groove weld?
Both prepare only one member while the other stays square. The difference is the shape of the preparation. A bevel groove has a straight angled cut. A J-groove has a curved (J-shaped) preparation with a defined root radius. The J-groove reduces weld metal volume on thick plate compared to a bevel, making it more economical for material over 1 inch thick. Both use the broken arrow convention and have the perpendicular leg on the left.
Can root radius and root face appear on the J-groove symbol?
No. Per AWS A2.4 §7.3.3, root radius (r) and root face (f) CANNOT be placed on the weld symbol line. They must appear in a referenced cross-section detail or note. This is a critical rule unique to J-groove and U-groove welds — other groove weld dimensions (angle, root opening, groove depth) can appear on the symbol, but radius and root face cannot.
What is the prequalified J-groove root radius in D1.1?
Per D1.1:2025 Figure 5.1, all prequalified single-J CJP joints (B-U8) specify a root radius of r = 3/8 inch (10 mm) with a root face of f = 1/8 inch (3 mm) and a root opening of R = 0 to 1/8 inch (0 to 3 mm). Any other root radius requires qualification by testing (PQR). The groove angle is 45° for SMAW all positions and 30° for GMAW/FCAW all positions. All prequalified J-groove CJP joints require backgouge.
Why use a J-groove instead of a V-groove?
J-groove preparation reduces the volume of weld metal needed compared to V-groove on thick plate. For material over 1 inch thick, the curved preparation removes less base metal than a full V-opening, resulting in less filler metal consumption, less heat input, less distortion, and faster welding. The tradeoff is that J-groove preparation requires machining or special cutting equipment, while V-groove can be flame-cut.
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