What is the difference between a CJP and a PJP groove weld?

A complete joint penetration (CJP) groove weld fuses the full thickness of the joint, achieving 100% of the base metal cross-section. A partial joint penetration (PJP) groove weld is designed to a specified effective throat less than the full base metal thickness. Under AWS D1.1:2025, CJP welds in prequalified joint details do not require PQR testing; PJP welds also fall under the prequalified program but carry explicit effective-throat rules.

When does AWS D1.1:2025 require a CJP weld versus allow a PJP weld?

AWS D1.1:2025 does not mandate CJP over PJP in most cases — the structural engineer specifies weld type based on design loads, fatigue, and connection geometry. However, CJP is required in seismic-force-resisting system (SFRS) moment connections per AISC 341, and CJP is generally required where the full tension capacity of the base metal must be developed.

Can a prequalified PJP groove weld be used without a PQR?

Yes, if the joint detail and welding process match one of the prequalified joint details in AWS D1.1:2025 Annex I (Figure I.2 for PJP details). The WPS must document the groove angle, root opening, and the calculated effective throat. A PQR is only required when departing from prequalified joint geometry.

How is the effective throat for a PJP groove weld calculated?

For PJP groove welds made by SMAW, GMAW, or FCAW at groove angles ≥60°, the effective throat equals the groove depth. For groove angles between 45° and 60°, the effective throat is the groove depth minus 1/8 in [3 mm]. At angles below 45°, prequalification is not available — a PQR is required.

CJP vs PJP Groove Welds: Prequalified Joint Selection

How to choose between complete joint penetration and partial joint penetration groove welds under AWS D1.1:2025 prequalified joint details. Practical guidance for CWIs and fabricators.

Why the CJP / PJP Distinction Matters on the Shop Floor

The decision between complete joint penetration and partial joint penetration groove welds gets made by the structural engineer — it shows up on the drawings as a weld symbol with or without a depth-of-bevel callout. But from the WPS and inspection perspective, the distinction shapes everything downstream: which prequalified details you can use, how you calculate effective throat, what NDE you must perform, and how the weld will be inspected for acceptance.

CWIs and QC managers who understand the underlying logic — not just the symbol reading — can catch design errors, flag PJP welds used in applications that actually require CJP, and write WPS documents that correctly characterize what is being welded.

CJP Groove Welds: The Full-Penetration Standard

A complete joint penetration groove weld deposits weld metal through the full thickness of the thinner joined member. The term is geometric: the weld reaches and fuses the root of the joint completely. In practice, this means:

Single-pass CJP is rarely achievable for plates thicker than about 3/8 in without a backing bar.
Backing bars (permanent steel backing or removable ceramic/copper) are common for CJP joints welded from one side.
Back gouging and seal pass is the alternative for two-sided access: weld from one side, gouge or grind to clean metal from the other side, confirm no cracks or incomplete fusion, then weld from the second side.

AWS D1.1:2025 prequalified CJP joint details (Annex I, Figure I.1 joint types B, TC, BC series) specify groove angle, root opening, and root face geometry. A WPS written to a prequalified CJP detail with one of the listed processes (SMAW, GMAW, FCAW, SAW, GTAW, FCAW-S) does not require a PQR. Prequalification applies to the joint geometry and process combination, not to the operator — welders still require WPQ qualification under Clause 6.

PJP Groove Welds: Effective Throat Is the Design Quantity

A partial joint penetration groove weld is specified by its effective throat — the dimension the engineer used in the weld capacity calculation. Unlike a fillet weld (where effective throat = 0.707 × leg), the PJP groove weld effective throat is tied to the groove angle and depth through explicit AWS D1.1:2025 rules.

Effective throat by groove angle:

Groove Angle	Effective Throat (SMAW, GMAW, FCAW, GTAW)
≥60°	= Groove depth
45° to <60°	= Groove depth − 1/8 in [3 mm]
<45°	Not prequalified — PQR required

For SAW single-pass PJP welds, the 45°–60° reduction also applies, and maximum groove depth-to-width ratio constraints limit prequalification further.

Rule library based on AWS D1.1:2025; verify against your governing edition — the AHJ or contract may specify 2020 or earlier.

The practical consequence: if a drawing calls for a PJP with 1/2 in effective throat on a 5/8 in plate, the fabricator must select a groove geometry that delivers that effective throat. A 60° included bevel to the required groove depth (1/2 in below the plate surface) qualifies if using SMAW or GMAW. A shallower groove angle at the same depth would require either the depth-reduction correction or a full PQR.

When CJP Is the Only Acceptable Answer

AWS D1.1:2025 does not designate "all primary tension connections shall be CJP" — that determination is structural and comes from the engineer or a governing standard. But several scenarios make CJP effectively mandatory:

AISC 341 seismic connections. Moment connections in special and intermediate moment frames (SMF/IMF) require CJP groove welds in the beam-flange-to-column-flange joints. AISC 341-22 Section 7.3b lists the requirements explicitly, and the WPS must reflect the CJP requirement and meet the toughness provisions for the filler metal. A PJP in a designated seismic connection is a nonconformance regardless of the computed capacity.

Tension members where full cross-section must be developed. If the structural engineer has designed the connection assuming the full net-section area of the base metal is engaged in tension transfer, a PJP is insufficient — its capacity is limited by the effective throat.

Fatigue-critical applications. CJP welds, when made from two sides (or from one side with backing removed and the root backgouged), produce a more uniform stress field than PJP welds. AISC 360 Table A-3.1 assigns PJP groove welds to lower fatigue categories than CJP, so fatigue-governed designs frequently mandate CJP.

Fracture-critical members (FCM). Bridge and aerospace applications governed by AASHTO or FAA specs often require CJP on fracture-critical members, and the NDE requirements (UT or RT) typically apply only to CJP joints.

Prequalified Joint Details: Navigating Annex I

AWS D1.1:2025 Annex I contains the prequalified weld joint details. For groove welds, the tables are organized by weld type and position. Key reference points:

Figure I.1 — prequalified groove weld joint details for CJP (butt, T-, and corner joints)
Figure I.2 — prequalified groove weld joint details for PJP

Each detail specifies:

Applicable processes
Groove angle range (sometimes narrow, sometimes a range)
Root opening (R) tolerance
Root face (f) tolerance
Permitted welding positions
Whether backing is required or optional
Notes for specific process limitations (e.g., SAW single-pass vs. multipass restrictions)

A WPS written to a prequalified joint must document the groove geometry precisely as specified in the detail. Minor departures — a groove angle slightly outside the tabulated range, or a root opening wider than the maximum — take the joint out of the prequalified program and require a PQR. The WPS is the document that proves the joint was within the prequalified bounds; inspectors will look at this during audit.

NDE Implications

The CJP/PJP distinction drives NDE requirements:

CJP groove welds: AWS D1.1:2025 Clause 8 requires UT or RT for CJP groove welds in statically loaded connections above the applicable section tension limit, and for all CJP welds in cyclically loaded structures. The NDE must be performed after PWHT (if applicable) and cover the full weld length.

PJP groove welds: AWS D1.1:2025 does not mandate volumetric NDE (UT/RT) for PJP groove welds under static loading — the effective-throat reduction already accounts for the incomplete fusion at the root, which is expected and designed-for. Visual inspection and, where specified, MT or PT for surface conditions are the typical requirements.

Key error pattern to catch: a connection drawn as PJP that the engineer actually intended as CJP (design capacity check was for a CJP) but fabricated and inspected as PJP. The root will show an unfused area that is acceptable for a true PJP but is a defect for a CJP joint. If the NDE requirement is absent (because the CWI classified it as PJP), the defect is never found. This underscores why QC managers need to reconcile the weld symbol with the connection capacity table in the structural engineer's calculations when the weld type is ambiguous.

How the WPS Documents the Distinction

On the WPS form (AWS Annex M format), the weld type — CJP or PJP — appears in the "Joint Design" section. For PJP, the WPS must also specify:

Groove angle (the angle as fabricated, not just "per drawing")
Effective throat (the minimum acceptable value after the groove-angle reduction is applied)
Root opening and root face (ranges from the prequalified detail or the qualified range from the PQR)
Whether permanent backing is used (and backing bar specification if so)

The WPS does not need to repeat the structural capacity calculation — that is the engineer's domain. But the WPS must be specific enough that the fabricator and CWI can independently verify that the joint as fabricated meets the prequalified detail and delivers the specified effective throat.

For more on WPS essential variables and joint geometry documentation, see AWS D1.1 Table 6.6 Essential Variables Explained and WPS Submittal Package: EOR Review Checklist.

Common Field Mistakes

Groove angle measured after fit-up vs. as-designed. A 60° included angle on the drawing means 30° bevel per plate. If the fitter bevels both plates to 25° and closes the root opening slightly, the fit-up angle may look acceptable visually but the effective throat reduction now applies. Require a bevel angle inspection before tacking.

PJP used where AISC 341 requires CJP. This is most common in retrofit projects or when the connection design is delegated to the steel detailer rather than the EOR. The fabricator's WPS program should flag all seismic frames for mandatory CJP review.

Skipping the effective-throat note on the WPS. Writing "PJP, per drawing" without specifying the effective throat leaves the CWI with no acceptance criterion during inspection. If the groove is underfilled, there is no documented minimum to reject against.

If your WPS program needs to cover both CJP and PJP joint families across multiple base metals and processes, see how a complete procedure library is structured at /pricing.