Complete Joint Penetration (CJP) Weld — D1.1:2025 Guide
A complete joint penetration weld extends through the full thickness of the base metal joint. Under D1.1:2025, prequalified CJP groove joints per Clause 5.4.1 and Figure 5.1 require no PQR. Non-prequalified CJP procedures must be qualified by testing per Table 6.2.
What Is a CJP Weld?
A complete joint penetration (CJP) groove weld is a weld in which the weld metal extends through the full thickness of the joint. The weld fuses completely from one surface to the other, creating a joint with the same cross-sectional strength as the base metal itself.
CJP welds are required wherever the joint must carry the full design load of the connected members. In structural steel, this includes moment connections in rigid frames, heavy bracing connections, column splices in seismic applications, and any joint where the engineer specifies full-strength performance. When a connection must transmit tension perpendicular to the weld axis, a CJP weld is typically the only option that satisfies D1.1 strength requirements without a reduced effective throat calculation.
The defining characteristic of a CJP weld is not the groove type — it is the completeness of fusion. V-groove, bevel, J-groove, U-groove, and even square groove welds can all achieve CJP when the weld metal fully penetrates the joint thickness. What matters is that no root area remains unfused.
Key distinction: CJP is defined by the result (full penetration), not the method. The same V-groove joint can produce a CJP weld when backgouged and backwelded, or a PJP weld when welded from both sides without backgouging (Clause 5.4.2).
CJP vs PJP — When Each Applies
The distinction between CJP and PJP under D1.1 is defined by how the weld is executed, not just the joint geometry. Clause 5.4.1 governs CJP groove welds. Clause 5.4.2 defines PJP groove welds as groove welds without steel backing welded from one side, and groove welds welded from both sides but without backgouging.
| Attribute | CJP | PJP |
|---|---|---|
| Penetration | Full joint thickness | Partial — specified depth |
| Effective throat | Equals base metal thickness | Reduced — per Table 5.8 minimum |
| D1.1 clause | Clause 5.4.1 | Clause 5.4.2 |
| Prequalified details | Figure 5.1 | Figure 5.2 |
| Typical use | Moment connections, column splices, tension joints | Shear connections, stiffener welds, compression splices |
| Design strength | Full base metal strength | Must be calculated based on effective throat |
The engineer selects CJP when the connection must develop the full strength of the members. PJP is appropriate where the applied loads are less than the full capacity of the connected parts — and where the reduced effective throat is accounted for in design calculations. PJP welds are generally less expensive to produce because they require less weld metal and may not require backgouging.
Prequalified CJP Groove Joints
D1.1:2025 Clause 5.4.1 defines prequalified CJP groove weld details. CJP groove welds that match the configurations in Figure 5.1 may be used without performing the WPS qualification test described in Clause 6. This means no PQR, no test weld, and no destructive testing — provided every element of the procedure stays within the prequalified envelope.
Figure 5.1 contains dozens of prequalified CJP joint details organized by groove type: single-V, double-V, single-bevel, double-bevel, single-U, double-U, single-J, double-J, and square groove. Each detail specifies the root opening, groove angle, root face dimension, and whether backing is required. The dimensions are given as ranges with tolerances — the “As Detailed” column shows the design values, and the “As Fit-Up” column shows the acceptable variations per Clause 5.4.1.8.
To use a prequalified CJP joint, all of the following must be satisfied:
- Joint detail matches Figure 5.1
- The groove type, root opening, groove angle, and root face must match one of the prequalified configurations. Joint dimensions may vary within the tolerances shown in the “As Detailed” column per Clause 5.4.1.1.
- Approved welding process
- The process must be SMAW, SAW, GMAW (except GMAW-S short-circuit transfer), or FCAW. These are the only four prequalified processes under Clause 5.
- Approved base metal and filler metal
- The base metal must be listed in Table 5.6 and matched with an approved filler metal per Table 5.7. Verify your steel against Table 5.6 using your mill test report. Using a base metal not in Table 5.6 disqualifies the prequalified path entirely.
- Preheat and interpass temperature
- Minimum preheat must meet Table 5.11 requirements for the base metal category, welding process, and material thickness.
A typical structural building frame using A992 steel with single-V CJP joints, E71T-1 FCAW wire, and parameters within Clause 5 limits qualifies entirely under the prequalified path. No PQR required.
Backgouge and Backing Requirements
Backing and backgouging are among the most frequently misunderstood aspects of CJP welding. D1.1 does not require backing on every CJP weld — the requirement depends on whether the weld is made from one side or two.
When Backing Is Required
Clause 5.4.1.2 states that prequalified CJP groove welds made from one side only shall have steel backing. This is the default for single-sided CJP joints in Figure 5.1. The backing bar provides a surface for the root pass and helps achieve full penetration without burn-through.
When Backing Is Not Required
CJP welds do not always require backing. Clause 5.4.1.3 permits prequalified CJP groove welds without steel backing when two conditions are met: the backing is removed after welding, and the back side of the weld is backgouged to sound metal and backwelded. Double-sided CJP welds — where the joint is welded from both sides with backgouging — achieve full penetration without any permanent backing.
Backgouging removes the root of the first-side weld to expose sound weld metal, eliminating any lack-of-fusion or slag inclusions at the root. The backweld then completes the joint from the second side. This technique produces a CJP weld with no permanent backing bar embedded in the joint.
Practical note: Many engineers prefer backgouged CJP welds for fatigue-sensitive connections because the backing bar removal eliminates a potential stress concentration at the weld root. The choice between backed and backgouged CJP depends on access, cost, and fatigue requirements — not a blanket code requirement.
How to Qualify a CJP WPS
When a CJP groove weld falls outside the prequalified limits of Clause 5 and Figure 5.1, the WPS must be qualified by testing per Clause 6. Table 6.2 defines the number and type of test specimens required for CJP groove weld qualification, along with the range of thickness qualified.
The qualification test involves producing a test weld on plate (or pipe for tubular applications), extracting specimens, and performing destructive testing. For plate tests, Table 6.2 specifies visual testing (VT) per Clause 6.10.1, reduced-section tension tests, and either root and face bend tests or side bend tests depending on plate thickness. The plate thickness tested determines the range of base metal thickness qualified for production welding.
For plates 3/8 in and under, the test qualifies a minimum thickness of 1/8 in and a maximum of 2T (twice the test plate thickness). For plates over 1 in, the minimum remains 1/8 in and the maximum is unlimited. This means a single test on 1 in plate qualifies the procedure for all thicknesses from 1/8 in upward.
The essential variables recorded on the resulting PQR define the boundaries of the qualified WPS. Any change to an essential variable listed in Table 6.6 — welding process, filler metal classification, base metal group, position, preheat, or any of the other 35 listed variables — may require re-qualification.
How CJP Appears on a Welding Symbol
On engineering drawings, a CJP weld is indicated by showing the groove weld symbol (V, bevel, J, U, or square) without a depth dimension in the weld size position on the reference line. When no weld size (depth) is specified, the weld is understood to be complete joint penetration. If a depth dimension appears — such as “3/8” next to a V-groove symbol — the weld is PJP to that depth.
The groove angle, root opening, and root face dimensions appear in their standard positions on the welding symbol. If backing is required, the backing symbol (a rectangle on the opposite side of the reference line) is included. A tail note may specify the WPS number, welding process, or other supplementary information.
For a deeper dive into welding symbol conventions, see our groove weld symbol reference and complete symbol chart.
Frequently Asked Questions
No. D1.1:2025 Clause 5.4.1.2 requires steel backing for prequalified CJP groove welds made from one side only. However, Clause 5.4.1.3 permits CJP welds without steel backing when the backing is removed after welding and the back side of the weld is backgouged to sound metal and backwelded. Double-sided CJP welds with backgouging do not require backing at all. The backing requirement applies specifically to single-sided prequalified CJP joints.
CJP (complete joint penetration) means the weld metal extends through the full thickness of the joint. PJP (partial joint penetration) means the weld metal does not extend through the full thickness. Under D1.1:2025, the distinction depends on how the weld is made: groove welds without steel backing welded from one side, and groove welds welded from both sides but without backgouging, are considered PJP per Clause 5.4.2. CJP joints carry the full design strength of the base metal. PJP joints carry a reduced effective throat, and the engineer must account for this in the design.
A CJP weld is indicated on a welding symbol by showing the groove type (V, bevel, J, U, or square) without a depth dimension in the weld size position. When no depth dimension appears, the weld is understood to be CJP. If a depth dimension is shown, the weld is PJP to that depth. Additional information such as groove angle, root opening, and backing requirements appear in their standard positions on the symbol. A tail note may specify the WPS number or welding process.
Yes. D1.1:2025 Clause 5.4.1 defines prequalified CJP groove weld details. The joint configuration must match one of the prequalified details in Figure 5.1, including the specified groove type, root opening, groove angle, and root face dimensions. The welding process must be SMAW, SAW, GMAW (except short-circuit transfer), or FCAW. The base metal must be listed in Table 5.6, and all other Clause 5 provisions must be met. Prequalified CJP joints do not require a PQR or qualification testing under Clause 6.