Bead type — stringer or weave — looks like a purely technique question. It isn't. The choice has implications for heat input, fusion, distortion, and in certain cases the validity of the WPS itself. Getting this right on the procedure document matters more than many shops realize.
What the terms mean
A stringer bead is deposited by moving the electrode nearly straight along the joint axis with minimal lateral motion — usually less than two or three electrode diameters of weave. The bead is narrow, heat input is concentrated along a tight path, and the pass is roughly as wide as the electrode or wire diameter plus slag coverage.
A weave bead is deposited with deliberate oscillation across the joint — side to side, in a Z-pattern, crescent, or similar motion. A single weave pass covers more area and deposits more heat per linear inch of travel than a stringer bead.
Neither is categorically better. The right choice depends on joint geometry, material thickness, position, and the metallurgical requirements of the application.
Where AWS D1.1:2025 draws the line
Prequalified WPS: weave width is capped
Prequalified procedures under AWS D1.1:2025 (those that avoid a PQR by meeting all prequalification conditions) carry specific restrictions on bead size and configuration. The code caps weave bead width at a maximum of three times the nominal electrode diameter. Exceed that limit and the procedure is no longer prequalified — it requires a PQR-backed qualification test to be valid.
This limit is not arbitrary. Wide weave passes increase heat input, slow the freeze rate of the weld pool, and in some positions can compromise fusion at the toe. The prequalification system trades design flexibility for elimination of the test event; the weave cap is part of that bargain.
If your prequalified WPS says nothing about bead type, production welders may default to wide weave — and that's a compliance problem that won't surface until a third-party CWI inspects the job.
Qualified (PQR-backed) WPS: nonessential variable
For procedures qualified by test, AWS D1.1:2025 classifies bead type as a nonessential variable. Changing from stringer to weave — or vice versa — does not require a new PQR or even a WPS revision, as long as the WPS doesn't explicitly restrict it.
Nonessential doesn't mean undocumented. The WPS should indicate whether both bead types are permitted, or restrict to one, so the production welder has a clear instruction.
What to write on the WPS
The WPS form (AWS D1.1 Annex M or equivalent) includes a field for bead type or joint details. Fill it with one of these:
- "Stringer beads only" — clear restriction, used when heat input control or distortion is critical
- "Stringer or weave permitted; max weave width 3× electrode diameter" — covers both with the prequalification limit restated as a reminder
- "Stringer beads preferred; weave permitted for fill and cap passes" — common on multi-pass procedures where the root is run stringer for control and fill passes use weave for deposition efficiency
Leaving the field blank is a documentation deficiency. Auditors will note it. More practically, welders will fill in the blank with whatever is fastest.
Heat input consequences
Even when bead type is a nonessential variable, the heat input isn't. If the procedure has a maximum heat input limit — either from the engineering specification or from a CVN toughness requirement enforced by AWS D1.1:2025 Table 6.8 — then switching from stringer to weave may push heat input beyond the limit without triggering a requalification flag.
Example: A welder running 3G vertical with stringer beads at 35 kJ/in might push to 50 kJ/in by switching to a wide weave in the same joint. If the WPS cap is 45 kJ/in, the welder is out of bounds — even though bead type itself didn't trigger the violation. The heat input did.
Track heat input explicitly in production. Bead type change is often the mechanism, but the essential variable violation shows up in the energy calculation.
For more on how heat input is controlled and documented, see heat input control and documentation in WPS.
Deposition rate and productivity trade-offs
Wide weave beads deposit more metal per arc-on minute and reduce the number of passes needed to fill a joint. That productivity gain is real — but it comes with the obligations above.
On thick-plate multi-pass joints (3/4 in and up), shops often use stringer beads for root and hot passes, then open up to weave for fill passes where heat input and dilution are less critical. That's acceptable if the WPS authorizes both techniques and the welder doesn't exceed the heat input envelope.
On thin material (3/16 in and below), weave is rarely appropriate. The wider heat path can burn through or cause significant distortion.
Position and bead type
Bead type interacts with position. In flat (1G) and horizontal (2G) position, wide weave passes are easier to control. In vertical (3G, particularly vertical-down), weave passes require experienced technique — the weld pool is less stable, and a wide oscillation can cause undercutting or lack of fusion.
Some WPS restrict position-specific bead type: stringer only in overhead and vertical-up, weave permitted in flat and horizontal. This is a practical engineering decision, not a code requirement, but it belongs in the procedure document so the welder has clear guidance.
See welding position qualification limits under AWS D1.1 for how position restrictions interact with the procedure qualification matrix.
Process-specific notes
SMAW (stick): Stringer beads are the default for most structural applications. Weave passes are permitted but demand good technique to avoid lack of fusion at the toes on vertical and overhead passes.
GMAW (MIG): Short-circuit transfer favors stringer beads for control. Spray and pulsed-spray transfer can handle modest weave. Wide weave in GMAW risks cold-lapping at the toes if travel speed drops.
FCAW: Similar to GMAW. Self-shielded FCAW (FCAW-S) is more sensitive to wide weave patterns — the slag system in FCAW-S is designed for a specific pool shape, and wide oscillation can disrupt it.
SAW: Automatic SAW runs stringer beads by nature of the process configuration. Weave is not typically discussed in SAW procedure documentation.
Putting it in the WPS
When you write the procedure — or review one for a shop audit — check these four things on bead type:
- Is the bead type field populated (not blank)?
- If the WPS is prequalified, does it reference the weave width limit?
- If heat input is capped (CVN application or engineering spec), is the bead type restriction consistent with that cap?
- Are position-specific restrictions noted if the procedure qualifies multiple positions?
If all four are addressed, the WPS is clean on this variable. If any are missing, the procedure needs revision before production welds begin.
For a full checklist of what a CWI reviews on a WPS document, see CWI WPS review checklist. For software that enforces these fields automatically, see WPS Welding's procedure builder.
Rule library based on AWS D1.1:2025; verify against your governing edition. The AHJ or contract may specify 2020 or an earlier edition, which may carry different bead type restrictions under prequalification.