Skip Weld Symbol Explained: How to Read Length-Pitch Notation, Chain vs. Staggered Layouts, and Rules

A fabricator on a busy structural shop floor once welded every stiffener seam full length because he read ‘3-6’ as ‘weld 3 inches, then leave 6 inches.’ The drawings meant three inches of weld at a six-inch pitch — center to center — and half a day of grinding plus a re-inspection proved that a two-character misunderstanding can be expensive. That is exactly why the skip weld symbol deserves a careful, unhurried look.

It Looked Like Three Simple Marks on the Drawing — Until the Parts Came Out Wrong

A fabricator on a busy structural shop floor once welded every stiffener seam on a base plate full length. The drawing said 3-6 next to an ordinary fillet weld symbol. He read it as “weld 3 inches, then leave 6 inches of gap.” The drawing meant something entirely different: 3 inches of weld at a 6-inch pitch, measured center to center. A day of grinding, a re-inspection, and a costly delay proved what every seasoned welder already knows — a two-character misunderstanding on a weld symbol is expensive.

That is exactly why the skip weld symbol deserves a careful, unhurried look. If you searched for “skip weld symbol,” you are probably here for four practical reasons: you want to know what it means, how to read it, when it is appropriate, and what mistakes to avoid. This article answers all four, in that order, with worked examples you can take back to the shop.

What Is a Skip Weld, Plain and Simple?

A skip weld is a weld that is deliberately not continuous. Instead of one unbroken bead down the whole joint, the welder lays short segments with unwelded spaces between them. An AWS-aligned textbook definition puts it cleanly: “An intermittent weld, also called a skip weld, consists of a series of welds placed on a joint, with unwelded spaces between each of the welds.” The terms “skip weld” and “intermittent weld” are used interchangeably in industry.

Here is the point that trips up most beginners: there is no separate “skip” glyph in the welding symbol alphabet. If you flip through AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination — the reference standard for weld-symbol syntax in the United States — you will not find a unique mark for skip welds. Instead, a skip weld is called out with an ordinary fillet or groove weld symbol plus a length-and-pitch dimension such as 3-6 (imperial, in inches) or 75-150 (metric, in millimeters). The “skip” part lives entirely in the numbers, not in the shape.

The same convention is governed elsewhere: ASME Y14.36 covers the same territory for ASME drawings, and ISO 2553 governs international work. If you read a drawing from an overseas fabricator, the notation will look familiar, though the reference line conventions may differ — more on that later in the article.

Why the Numbering Matters More Than the Symbol

Since the symbol itself is standard, the entire risk sits in the two numbers. In 3-6, the first number is the segment length (how long each individual weld is) and the second is the pitch (the spacing from one segment to the next). The pitch is always measured from the middle of one weld to the middle of the next — never edge to edge. That single distinction is what turned our opening story into a rework job.

The reason designers bother with skip welds at all is compelling. Lincoln Electric reports that substituting intermittent welds for continuous welds can reduce deposited weld metal by as much as 75 percent, and ESAB puts the weld-metal volume reduction at roughly 70 percent in its distortion-control guidance. Less weld metal means less heat, less distortion, lower consumable cost, and less grinding. But the trade-off is a joint with genuinely reduced strength, which is why knowing when to use skip welds — and when never to — is a professional skill, not a minor detail. For background on how short, controlled weld segments behave in practice, our MIG tack weld guide covers spacing, sizing, and settings for exactly this kind of work.

What This Article Covers

We will take the symbol apart piece by piece, teach you a repeatable four-step reading method with worked examples, and compare the two layout patterns — chain and staggered intermittent. From there we get into the engineering case for welding less metal, the joints where skip welds work well and the joints where they are dangerous, the numeric limits in codes like AWS D1.1, and the seven most common mistakes that lead to rejected work. We will also clear up an overloaded term — the difference between the skip weld symbol and the skip welding technique — before finishing with hands-on layout, welding, and inspection tips.

Keep one sentence in mind as you read the rest of this article: the skip weld symbol is not a special mark to memorize, it is a dimensioning discipline to master. Get the two numbers right, and everything else follows.

Anatomy of a Skip Weld Symbol: Reference Line, Arrow, Tail, and Dimensions

Before you can read a skip weld callout, you need to know where each piece of information lives. The reassuring part: there is no hidden “skip weld glyph” buried in the standards. A skip weld is drawn with the same core welding symbol everyone already sees on structural drawings, plus one habit: a pair of dimensions sitting to the right of the weld symbol.

The Five Parts of a Welding Symbol

Every welding symbol you will meet in AWS A2.4 practice is assembled from five components, as outlined in Miller Welds’ guide to reading and understanding weld symbols:

• Arrow line: a leader pointing directly at the joint to be welded. If the arrow touches more than one joint, supplementary detail such as an all-around symbol or a specific note clarifies the target.
• Reference line: the horizontal spine of the symbol. Everything else hangs off it, and everything meaningful is read from it.
• Basic weld symbol: the little triangle, box, or V that identifies the weld type, such as fillet, square groove, V-groove, plug, or spot.
• Dimension and supplementary data: leg sizes, segment lengths, pitch, root openings, number of welds, and other numbers. This is where skip weld information lives.
• Tail: a fork-shaped bracket at the end of the reference line, used for process or reference notes.

Arrow Side vs. Other Side: The Golden Rule of Placement

The single most important reading rule is positional, and the National Board of Boiler and Pressure Vessel Inspectors states it plainly: information written below the reference line applies to the arrow side of the joint, and information written above the line applies to the other side.

The arrow touches one face of the joint, and that face is the arrow side; the opposite face is the other side. So a fillet triangle sitting below the line means “put a fillet weld on the side the arrow points to.” A symbol above the line means the other side, and symbols on both sides mean weld both. This convention applies to every dimension on the symbol, including skip weld length-pitch pairs.

Where the Skip Weld Dimensions Sit

Here is the key insight that trips up beginners: the skip aspect of a skip weld symbol is a dimensioning convention, not a shape. There is no special glyph to look for. For an intermittent weld, the segment length is placed to the right of the basic weld symbol, followed by a hyphen and then the pitch. A fillet triangle below the line with “3-6” written beside it reads: arrow-side fillet weld, three inches of weld at a six-inch pitch.

The dimensions always follow the weld symbol horizontally, and they inherit its side. If the “3-6” sits below the reference line with the triangle, both the weld and the skip dimensions apply to the arrow side. If a matching pair sits above the line, the other side gets the same pattern. That inheritance is exactly how chain and staggered layouts are communicated, which the next section unpacks.

The convention is not limited to fillet welds, since groove welds use the same length-pitch grammar. AWS A2.4 clause 4.5.4 covers staggered intermittent groove welds specifically, requiring the dimensions to appear on both sides of the reference line so the offset between the two rows is unambiguous. Whether you see a triangle or a V, the numbers to the right follow the same rules.

A Worked Walkthrough of One Symbol

Take a symbol that many fabricators meet on their first structural job: an arrow pointing to a stiffener-to-plate joint, a reference line, a fillet triangle below the line, “1/4” to the left of the triangle, and “3-6” to its right, with no tail.

1. The arrow identifies the joint.
2. Below the line means arrow side.
3. The triangle means fillet weld; the 1/4 is the leg size.
4. “3-6” means three-inch segments at six-inch pitch.
5. No tail means no special process or procedure note is required.

If you are newer to fillet sizing and leg-size conventions, our deeper guide on the fillet weld symbol, tack spacing, and sizing rules walks through the same reading process with more examples. Once the anatomy is familiar, everything that follows in this article is simply decoding the numbers to the right of that little triangle.

How to Read a Skip Weld Symbol Step by Step (With Worked Examples)

Reading a skip weld symbol is not a talent you are born with. It is a four-step routine you can run in about fifteen seconds once it becomes habit. Once it is habit, you can stand in front of any drawing on any shop floor and know exactly what the designer wants before you strike an arc. Let us build that routine, then test it against three worked examples.

The Four-Step Reading Method

1. Follow the arrow to the joint. The arrow points at the specific joint being welded. If it lands on a lap joint, an edge, or a corner, that is the connection the symbol governs, not the one six inches away.
2. Decide arrow side or other side. Everything drawn below the reference line applies to the arrow side of the joint. Everything drawn above the line applies to the other side. This one rule resolves most shop confusion.
3. Identify the basic weld type and its size. A right-angle triangle means fillet weld. A V between two angled legs means a V-groove. A square U means a square groove. The number to the left of that symbol is the leg size for a fillet or the depth of preparation for a groove.
4. Decode the dimensions left to right: size, then segment length, hyphen, pitch. As Miller’s weld symbol guide explains, the dash separates the length of each portion of the weld from the spacing of the welds, with length first and spacing second.

Skip welds live entirely in that fourth step. There is no special glyph for intermittent welding. It is ordinary dimensioning hung on an ordinary weld symbol, which is exactly why it gets misread so often.

Worked Example 1: A 3-6 Chain Fillet on the Arrow Side

Picture a fillet triangle drawn below the reference line with the dimensions ¼ – 3 – 6. Read it in order. The quarter-inch is the leg size of every segment. The 3 is the length of each individual segment. The 6 is the pitch, measured center to center. Because the symbol sits below the line, every one of those segments lands on the arrow side of the joint. Your gap is gap = pitch − segment length = 6 − 3 = 3 inches of unwelded joint between segments.

Here is the most important sentence in this section: the pitch is measured from the center of one segment to the center of the next, not from edge to edge. Reading it as an edge-to-edge gap is the most common misreading in the industry, and it produces segments spaced twice as far apart as the designer intended.

Worked Example 2: A Size With No Pitch

Now the same triangle, but the dimensions read only ¼ – 6. There is no third number, so there is no intermittency. A number without a pitch dimension specifies a continuous weld 6 units long. If the designer wanted skip welds, the pitch would be there. When you see a lone length, weld it solid for that length, stop, and move on. Assuming it is intermittent is how a fabricator ends up with a joint that is 40 percent short of its required weld metal.

Worked Example 3: A Staggered Pair Above and Below the Line

Look for a symbol with dimensions on both sides of the reference line. A fillet triangle below the line reading ¼ – 3 – 6 and another triangle above the line reading ¼ – 3 – 6 tells you two rows of intermittent welds, one on each side of the joint, whose segments are offset rather than directly opposed. As the TWI weld symbol reference and AWS A2.4 both set out, staggered intermittent welds are dimensioned on both sides of the reference line precisely so the offset relationship between the two rows is unambiguous. If both rows were identical and directly opposed, a single set of dimensions would be enough.

Metric drawings use the identical logic. A callout of 75-150 means each segment is 75 millimeters long at a 150-millimeter pitch, leaving a 75-millimeter gap. The units follow the drawing, so check the title block first. Our complete MIG setup guide covers the same title-block habit when dialing in machine settings.

Check Yourself

Try this mini-quiz before moving on. A symbol shows a 5/16 leg fillet below the reference line with dimensions 5/16 – 2 – 6. What side of the joint gets welded? Arrow side. How long is each segment? Two inches. What is the pitch? Six inches, center to center. What is the gap between segments? Four inches. Is there a second row on the other side? No, because nothing is drawn above the line. Answered all five correctly? You can read a skip weld symbol unaided. Missed one, walk the four steps again: the method never changes, only the numbers do.

Chain vs. Staggered: Two Skip Weld Patterns and How Each Is Drawn

Getting comfortable with “3-6” is only half the job. The next question a reader has is almost always the same: if there are segments on both sides of the joint, which ones line up with which? There are only two standard answers, and they behave very differently on the shop floor. One is called chain intermittent, the other staggered intermittent, and the drawing conventions that express them are not interchangeable.

Chain Intermittent: Segments Directly Opposite

A chain intermittent fillet weld is one where the segments on opposite sides of the joint sit directly across from each other — same start point, same stop point, mirrored along the seam. The National Board’s reference material uses exactly that definition: segments “directly opposite” each other across the joint. On a 144-inch stiffener welded 3-6 chain, you would see a 3-inch bead on the arrow side, a 3-inch bead directly opposite it on the other side, a 2-inch gap, then the pattern repeats in lockstep.

Because both rows are identical, the symbol does not have to repeat itself. A single set of dimensions on one side of the reference line is enough when both rows match — the dimension is understood to apply to both sides. That is what keeps chain callouts so compact on busy structural drawings.

Staggered Intermittent: Segments Offset

In a staggered layout, the segments on opposite sides are deliberately offset so starts and stops never line up across the joint. The conventional offset is half the pitch: for a 3-6 callout with a 6-inch pitch, the far-side segment begins 3 inches away from where the near-side segment begins. That single geometric change is what prevents a row of aligned termination points from forming a continuous weak line across the plate.

The drawing has to say so explicitly. AWS A2.4 requires staggered intermittent dimensions to be given on both the arrow side and the other side of the reference line (clause 4.5.4 for staggered intermittent groove welds), so the reader can see that the two rows are intentionally out of phase rather than accidentally mismatched.

How the Layout Math Works

Chain layout is the simple one. Set one datum at the end of the joint, then mark every pitch increment: segment start, segment stop, gap, repeat. One set of marks serves both sides because the rows mirror each other. Chalk it once, weld both sides from the same marks, and the MIG tack weld spacing guide applies equally here — small tacks at each segment center hold the part while you work outward.

Staggered needs two grids. Start with the same chain grid for the arrow side, then add a second grid shifted by half the pitch for the other side. Worked example: a 60-inch panel edge welded 2-4 staggered. The gap is pitch minus segment length, so 4 − 2 = 2 inches of unwelded space per side. Arrow-side segments start at 0, 4, 8 … 56 inches (15 segments). Other-side segments start at 2, 6, 10 … 58 inches (15 segments). The center-to-center offset between the two rows is exactly 2 inches — half the 4-inch pitch. Total weld metal: 30 segments × 2 inches = 60 inches across both sides, or 50 percent coverage per side.

Why bother with the extra layout work? Because aligned starts and stops concentrate shrinkage in one plane, and staggered patterns distribute those forces along the joint instead. On long, thin panels that is the difference between a flat part and one that needs flame straightening. Chain, by contrast, wins whenever speed and easy measurement matter more than the last bit of distortion control — which is most structural stiffener work. Sheet-metal fabricators chasing flatness tend to go the other way; the TIG sheet metal guide walks through that trade-off in detail.

Why Designers Specify Skip Welds: The Case for Welding Less Metal

On the shop floor, welding less metal on a joint can sound like cutting corners. In practice, it is the opposite. When a designer writes a length-pitch callout such as 3-6 on a drawing, they are not being cheap. They are managing heat, cost, and schedule at the same time, and the fabricator who understands that logic reads the symbol with a lot more confidence.

Distortion Control: The Real Driver

Every weld bead expands as it heats and shrinks as it cools. That shrinkage pulls on the surrounding plate, and on a long joint the pull accumulates. The result is angular distortion, buckling in thin sections, and residual stress locked into the assembly. A continuous bead essentially applies one long, uninterrupted shrinkage force along the entire joint.

An intermittent weld breaks that force into short, separated events. Each segment heats a small local area, and by the time the next segment is placed, the previous one has cooled and stopped pulling. The Lincoln Electric distortion guide lists skip welding and back-step welding among the recognized techniques for controlling distortion in long welds, which is why you will see both the technique and the symbol show up on distortion-sensitive work.

The practical payoff is real: flatter assemblies straight out of the fixture, less time in presses, rollers, or heat straightening, and lighter fixturing overall. Anyone who has watched thin sheet oil-can after a long continuous pass already understands the value. If distortion on thin material is a recurring problem in your shop, our guide to stick welding sheet metal covers the same battle from the operator’s side.

The Savings Add Up: Consumables, Labor, and Time

The numbers behind intermittent welding are hard to ignore. Lincoln Electric states that intermittent welds can reduce weld metal by as much as 75 percent compared with continuous welding. ESAB reports that weld volume can be maintained at roughly 70 percent lower by using intermittent welding instead of continuous welding in appropriate applications.

Less deposited metal translates directly into shop savings:

• Consumables — less electrode, wire, and shielding gas per assembly.
• Labor and travel — shorter total arc time, faster travel across the joint, fewer passes.
• Finishing — less grinding, less spatter cleanup, less straightening.
• Fixturing — lower clamping and restraint demands because the shrinkage forces are smaller.

One caution on those percentages: the actual saving depends on the length-pitch ratio. A 3-6 pattern lays down roughly 50 percent of the metal a continuous weld would; a more aggressive callout saves more. The figures above describe the upper end of what is achievable, not a guarantee for every drawing.

Strength Comes From Total Effective Length

This is the part that surprises people new to intermittent welding: the joint is not automatically weaker. On long, lightly loaded fillet joints, such as brackets, stiffeners, and covers, strength is governed by the total effective weld length the calculation requires. Because each segment contributes its own full effective length, a designer can distribute that required weld metal into segments and achieve the same calculated capacity as a continuous weld of equivalent total length. Total capacity depends on the sum of the segment lengths, not on whether the weld runs without a break.

Specifiers have settled on a few common rules of thumb to go with that principle. One published engineering specification for weld callouts states that intermittent welds are preferred for any weld over about 10 inches long, and that intermittent welds should cover approximately 50 percent of the total joint length unless the drawing notes otherwise. Those two numbers explain why 3-6 and 2-4 style callouts dominate shop drawings: they land right around half coverage.

In short, skip welds let a designer buy exactly the strength a joint needs and nothing beyond it. The fabricator who grasps that intent stops seeing intermittent callouts as an inconvenience and starts seeing them as a work order that protects the assembly from distortion and the budget from waste. The next question, naturally, is where those savings are safe to take and where they are not.

Where Skip Welds Work — and Where They Should Never Be Used

A skip weld symbol is a permission slip, not a blanket instruction. It tells you the designer has decided that less weld metal is acceptable at that joint, for reasons that usually involve distortion, cost, or both. The real question a fabricator has to answer is whether the joint itself belongs in that category. Load type, service conditions, and joint length decide it, not habit.

Where Skip Welds Belong

Intermittent fillet welds earn their place wherever strength depends on the total effective weld length rather than on continuity, and wherever heat input is the bigger enemy. The usual good candidates:

• Brackets, clip angles, and mounting plates attached to columns, bases, or frames
• Stiffeners, ribs, and doublers running along long stretches of plate
• Lap joints in sheet fabrication, where a long seam joins two panels with light static loading
• Covers, access panels, and non-pressure enclosures that only need to stay put
• Tank shells, ship panels, and deck construction with many parallel stiffener joints
• Any long joint where controlling angular distortion and buckling outranks everything else

Shipbuilding and panel work are the classic intermittent-weld territory. Stiffener-to-shell joints in a hull are long, repeated by the hundreds, and extremely distortion-sensitive, which is why shipyard training material treats skip welding as ordinary practice rather than a special case. The NSRP and Ingalls welding curriculum builds its plate-joining instruction directly around these layouts. Sheet-metal shops see the same logic on lap seams, where a spot welder and an intermittent fillet are solving the same problem in different ways: joining a lot of length without dumping a lot of heat into the part.

The No-Go List: Where Continuity Matters

Some joints simply cannot be interrupted. The main exclusions:

• Pressure-retaining or leak-tight joints. Every unwelded gap is a potential leak path. Boiler, header, and pressure-vessel work follows its own acceptance rules for exactly this reason, as outlined by the National Board. Pressure and containment piping falls in the same bucket.
• Fatigue- and cycle-loaded joints. Each segment start and stop is a stress raiser, and the gaps break up the load path, so crack initiation happens sooner than it would in a continuous bead.
• Impact or dynamic loading. Shock loads amplify the same problem: the joint has to transfer force smoothly, not in chunks.
• Corrosive or submerged service. Unwelded gaps trap moisture, residues, and stagnant liquid against the faying surface.
• Very short joints. Below roughly ten inches there is not enough length to establish a dependable segment pattern, and the end conditions eat the whole run.
• The ends of members. Most fabrication specifications require welds to begin and terminate at the ends of a member, or to carry an end return, with intermittent segments reserved for the middle. This is standard structural practice under AWS D1.1.

Two failure modes are worth fearing. The mild one is an inspector rejecting the work and sending it back for full-length welding, which costs far more than doing it right the first time. The serious one is a joint quietly loaded beyond its reduced capacity because someone shortened the spacing or shrank the segment size without approval. Neither is a welding problem; both are a drawing-reading problem.

When a drawing puts a skip weld symbol somewhere that looks wrong for the service, do not fix it at the machine. Raise it before the arc is struck, and make sure the people reviewing the finished joint are working from the same rules you can check in our guide to gas line welding codes, safety, and purging requirements. The symbol tells you what the designer allowed; your job is to confirm the joint qualifies for it.

Design Rules, Limits, and the Math Behind a Skip Weld Symbol

Reading the symbol is only half the job. The other half is knowing which document tells you whether the weld you just read is actually allowed. Fabricators get tripped up here constantly, because two separate standards are usually in play at once, and they answer completely different questions.

Two Documents, Two Jobs: A2.4 Draws It, D1.1 Judges It

AWS A2.4 governs symbol syntax: where the size goes, where the segment length and pitch go, what the hyphen means, which side of the reference line counts as arrow side. It is pure grammar. A22.4 will happily tell you a drawing is syntactically perfect while saying nothing about whether that weld can carry a load.

Whether the joint itself is acceptable belongs to the construction code: for most structural steel in the United States, that is the AWS D1.1 Structural Welding Code — Steel. D1.1 sets minimum sizes, minimum segment lengths, throat and leg tolerances, and acceptance criteria. Other contracts swap in ASME BPVC Section IX for pressure work or an EN/ISO contract for international drawings, but the split stays the same: one standard decides how the instruction is written, another decides whether the instruction is legal.

The Two Limits That Matter Most

First, minimum segment length. AWS D1.1 sets a minimum length of 1-1/2 in. [40 mm] for each segment of an intermittent fillet weld. The reasoning is physical: the start and stop of any fillet is its weakest zone, where fusion is thinner and tie-in is partial. A segment shorter than about an inch and a half never develops its full throat across its own length, so it behaves like an oversized tack rather than a real weld. Add the start and stop crater at each end and a 3/4 in. segment carries almost no dependable metal.

Second, pitch is not optional. Under the A2.4 convention, a dimension without a pitch specifies a continuous weld of that length. If the designer meant intermittent, the pitch must appear. “3” alone is a three-inch continuous run; “3-6” is three inches of weld at a six-inch pitch. There is no third interpretation to guess at.

The Strength Math in Plain Language

Two formulas cover nearly everything a reader needs.

• Total effective weld length = number of segments × length of each segment. Pitch controls layout and how load is distributed along the joint — it does not change the sum.
• Fillet nominal strength per inch = 0.6 × F_EXX × 0.707 × leg size. The 0.707 converts leg size to throat, the 0.6 is the shear factor, and F_EXX is the electrode classification in ksi.

Put an E70 electrode with a 1/4 in. leg into that second formula: 0.6 × 70 × 0.707 × 0.25 ≈ 7.4 kips per inch of effective weld. (If you are still learning electrode numbering, our guide to what electrodes are in welding walks through the E70XX digits.)

Worked Example: A 144-Inch Joint, 3-6 Chain Pattern

Take a 12-foot stiffener seam specified as 3-6 chain fillet on both sides:

1. Centers fall every 6 in., so 144 ÷ 6 = 24 segments.
2. 24 × 3 in. = 72 in. of effective weld.
3. 72 ÷ 144 = roughly 50 percent joint coverage, and about half the weld metal of a continuous 3/16 or 1/4 in. fillet.
4. Capacity at 7.4 kips/in.: about 533 kips total, versus about 1,070 kips for a continuous weld of the same size.

That last line is the whole design trade-off in one comparison. The intermittent joint is not “stronger for less money” — it delivers roughly half the capacity at roughly half the cost. It is correct only when the calculated demand fits inside what the segments provide, which is exactly why the designer, not the welder, owns the spacing.

The numbers here are only as good as the conditions around them: proper fusion, correct leg tolerance, and a joint that is actually loaded the way the calculation assumes. Draw the symbol, verify the limits, do the arithmetic, and when the sheet does not add up, ask before you weld.

The 7 Most Common Skip Weld Symbol Mistakes (and How to Catch Them Early)

Most skip weld failures start on paper, not in the arc. The symbol is read, the layout is marked, and the error only surfaces at fit-up, inspection, or worse, in service. These seven mistakes show up again and again in shop conversations and trade forums. For each one, here is the symptom, what it costs you, and the fix.

1. Reading pitch as an edge-to-edge gap. Symptom: the fabricator treats “3-6” as three inches of weld, then a six-inch unwelded space. The real gap is pitch minus segment length — 6 − 3 = 3 units — because pitch is measured center to center. Consequence: total weld length doubles or halves compared to the drawing, distorting the joint and changing capacity. Fix: run the gap formula before marking, and lay out centers first, then each segment around its center.
2. Segment length with no pitch. Symptom: the symbol shows a length but no second number. Trade discussions treat this as an automatic ambiguity, because a lone length reads as a continuous weld of that size, which is why inspectors insist on the pitch whenever intermittency is intended (AWS forum discussion). Consequence: either an RFI stops the job or the shop guesses and gets rejected. Fix: if the drawing intends skip welds, the pitch must be printed. If it is missing, ask before striking an arc.
3. Staggered pattern dimensioned on one side only. Symptom: offset segments drawn above and below the reference line, but dimensioned on just one side. The offset information is destroyed and the drawing invites two different interpretations. Consequence: one crew lays out chain, the other lays out staggered, and the joint does not match. Fix: staggered layouts carry dimensions on both the arrow side and the other side — verify both before layout.
4. Flipping arrow side and other side. Symptom: the reader assumes the arrow always points the same way relative to the view instead of physically following it to the joint. Consequence: the weld lands on the wrong face of the connection, requiring removal and re-welding. Fix: trace the arrow to the actual joint on the detail, then place everything below the line (arrow side) or above the line (other side) from that joint’s perspective.
5. Missing or unspecified weld sizes. Symptom: a skip callout with no leg or throat dimension. Structure Magazine reports that structural drawings frequently carry welding symbols with unspecified sizes, leaving the fabricator to guess throat or leg dimensions (Commonly Misapplied Welding Symbols). Consequence: undersized welds fail capacity checks, oversized welds burn through thin plate. Fix: make weld size a required field on every drawing check and raise an RFI the moment it is blank.
6. Unit confusion on mixed drawing sets. Symptom: an inch-based detail stapled to a millimeter-based schedule, or a “75-150” callout laid out in inches. Consequence: spacing errors that are easy to miss until fit-up or inspection, when rework is expensive. Fix: confirm the unit system per sheet at the start of the job and write it on the layout board.
7. Improvised spacing by the fabricator. Symptom: the crew shortens pitch or shrinks segment size because it “looks better” or welds faster. Consequence: inspectors reject the work outright, and a joint loaded beyond its reduced capacity is the failure mode nobody wants. Fix: spacing is a design decision, not a shop convenience. Any deviation goes through the engineer before welding starts.

Catch most of these with a two-minute drawing check: read the dimensions aloud, sketch the pattern in the margin, and confirm it against the joint before any metal is marked. Six of the seven mistakes above are caught by that habit alone.

Skip Weld Symbol vs. Skip Welding Technique vs. Continuous Weld: A Clear Comparison

Here is a mix-up that causes real arguments on the shop floor: two welders hear the phrase \”skip welding\” and walk away with different ideas. One hears a drawing instruction that permanently reduces how much metal goes into a joint. The other hears a work sequence for laying the same full weld metal in a different order. Both are correct, and neither is the other. Sorting out the skip weld symbol, the skip welding technique, and a plain continuous weld is the difference between reading a drawing and guessing at it.

The Skip Weld Symbol: A Permanent Design Decision

A skip weld called out by symbol is an instruction from the designer about the finished joint. When a drawing shows a fillet symbol with \”3-6\” beside it, the finished part is meant to have three-inch segments at six-inch centers, and nothing else. The unstated portions stay unwelded for the life of the structure. That means less weld metal is deposited, period. It also means less total heat ever enters the part, because the skipped areas never see an arc at all. This is the version of \”skip welding\” covered in the weld-symbol charts in Miller’s weld-symbol reading guide.

The Skip Welding Technique: A Sequence, Not a Specification

Skip welding as a technique is a distortion-control sequence. The welder deposits a short length at one position, moves elsewhere, welds another short length, and works back until the joint is filled. Lincoln Electric’s distortion guide groups skip welding with back-step, leapfrog, and balanced sequences. The critical difference: the finished joint still carries full, continuous weld metal. Nothing is left out. The heat is simply redistributed so it does not pile up in one direction and pull the assembly out of shape.

That distinction drives the thermal math. A symbol-specified skip weld removes weld metal outright, so it delivers the larger total heat reduction. A skip-welding sequence mostly moves the same heat around. On a heavy assembly where the drawing demands a full groove weld, sequencing is your only option. On a lightly loaded bracket where the drawing calls for 3-6, no clever sequencing substitutes for what the symbol specified.

Three Options Compared Side by Side

Continuous welding wins whenever service demands it: a leak-tight vessel, a fatigue-cycled connection, or a pressure-retaining seam gets full weld metal every time. Intermittent welding wins on cost, speed, and distortion where the code and service condition allow it. Sequencing sits in between — it buys distortion control without giving up a single inch of designed weld.

Don’t Trip Over the Standards: A2.4, Y14.36, and ISO 2553

The three systems describe the same joints differently, so confirm which one governs before you interpret a single dimension:

• AWS A2.4 — the baseline US convention. A single reference line; dimensions below the line apply to the arrow side, above the line to the other side. TWI’s weld-symbol reference explains the system well.
• ASME Y14.36 — the ASME counterpart used on ASME-format drawings and equipment documentation. Symbol content closely aligns with AWS, but formatting and title-block references differ, so read against the cited standard.
• ISO 2553 — the international convention. It resolves arrow-side ambiguity with a forked (double) reference line and uses tail notes for process references. A dimension sitting on the ident line of the fork can mean the weld goes on both sides — a trap if you trained on AWS drawings.

The practical rule: the drawing’s title block decides which rulebook you follow. A set stamped to ISO 2553 will not be graded by AWS habits, and the reverse is equally true. When in doubt, escalate — the same habit covered in pipe welding procedure documentation applies here: nothing gets welded on an assumption.

Get these three ideas straight and skip weld interpretation gets much easier. Continuous weld is the default full-strength joint. Intermittent by symbol is a designed reduction with less metal and less heat. Skip welding as a technique keeps every inch of weld but spreads the heat. Read the symbol, know the standard, and sequence the heat — in that order.

Practical Tips: Laying Out, Welding, and Inspecting a Skip Weld Joint (Plus Final Takeaways)

A skip weld symbol is a drawing instruction, but on the floor it becomes a series of physical tasks: mark the joint accurately, weld the segments in an order that keeps the assembly straight, and verify the result before the inspector finds the problem for you. This closing section turns everything covered earlier into a working routine, plus the escalation rule that protects both the fabricator and the engineer.

Layout: Mark Centers, Never Gaps

Start with arithmetic, not the soapstone. Convert the length-pitch callout into an unwelded gap: gap = pitch − segment length. A 3-6 pattern produces 3-inch weld segments separated by 3-inch bare gaps. A 75-150 metric callout produces 75 mm welds with 75 mm gaps. Write that gap down, then confirm the symbol really does call for intermittent welds before the first mark lands on the plate.

Now pick a single datum: the end of the member, a hole centerline, or a trim edge. From that one reference, mark the center point of every segment at pitch increments. Do not chain-measure from one segment end to the next. Small taping and eye errors stack, and over a long joint the spacing can drift far enough that a middle segment ends up welded on top of an end weld. Around each center, strike a start line and a stop line half a segment length either side. Soapstone or a paint marker works; avoid scratch awls on anything fatigue-sensitive, and suit up properly for the grinding that follows layout corrections, as covered in our welding PPE guide.

Welding Sequence: Ends First, Middle Balanced

Weld the ends of the joint first. Terminations usually carry full-length welds or end returns, and locking them in early gives shrinkage a stable anchor instead of letting the assembly walk out of square. Then fill the middle in a balanced or back-step order, alternating segments from opposite ends rather than marching in one direction, so heat does not pile up at a single end. That is the same reasoning behind Lincoln Electric’s distortion-control guidance.

Keep segment length, arc settings, and travel speed consistent from the first segment to the last. A 3-1/4 inch “3” and a 2-3/4 inch “3” are two different welds, and only one of them is on the drawing. If you are still building a repeatable short-length rhythm, the MIG tack weld guide covers consistent short-bead deposition and spacing control that transfer directly to intermittent fillets.

Inspection: Six Checks Before the Inspector Arrives

• Segment length against the code minimum. AWS D1.1 sets a 1-1/2 in. [40 mm] minimum length for each intermittent fillet weld segment (AWS D1.1), so segments may be shortened only within that limit and only with engineering approval.
• Pitch measured center to center along the full joint, never edge to edge.
• Segment count compared against the layout sheet while fit-up is still open and accessible.
• Pattern confirmed as chain or staggered against the symbol, including both sides where both are dimensioned.
• Leg size checked with a weld gauge, never judged by eye.
• End conditions verified: ends and end returns present wherever the drawing requires them.

Inspect every segment stop for undercut and crater cracks. Craters at stops are one of the most routine rejects on intermittent welds, and a quick dab of crater fill saves a repair cycle.

Escalation: Ambiguity Goes to the Engineer, Not the Floor

Missing weld size, missing pitch, a staggered pattern dimensioned on one side only, or a mixed metric-and-imperial drawing set are not judgment calls for the person holding the torch. Put them in writing as a request for information before the arc is struck. Shop-floor improvisation on spacing or segment size is the fastest route to a rejected joint and, worse, a joint loaded beyond its reduced capacity.

Final Takeaways

Read length-pitch as center-to-center. Know which pattern the symbol demands, chain or staggered. Verify segment length and spacing limits against the applicable structural code. And when anything on the drawing is unclear, ask before welding. A skip weld joint rewards preparation far more than speed: a correctly laid out, consistently welded, and properly documented intermittent joint is almost always faster than the rework it avoids. Return to our broader weld symbol reference whenever a new callout appears, and you will never again read “3-6” as an instruction to leave six inches bare.

Frequently Asked Questions

Is there a separate symbol for a skip weld?

No. There is no unique ‘skip’ glyph in AWS A2.4 or ISO 2553. A skip (intermittent) weld is shown with an ordinary fillet or groove weld symbol plus a length-pitch dimension such as 3-6 placed to the right of the symbol.

What does 3-6 mean on a weld symbol?

It means each weld segment is 3 units long (inches or millimeters, depending on the drawing) and the pitch is 6 units measured center to center. The actual unwelded gap is 3 units, because gap = pitch − segment length.

Is pitch measured center-to-center or edge-to-edge?

Always center to center. That is why a 3-6 pattern leaves a 3-unit gap, not a 6-unit gap — reading pitch as a gap is the most common skip weld symbol mistake and a frequent cause of rejected work.

What is the difference between chain and staggered intermittent welds?

In chain intermittent welds, segments on opposite sides of the joint sit directly opposite each other. In staggered welds, they are offset — typically by half the pitch — which spreads heat and shrinkage more evenly. Staggered patterns must be dimensioned on both sides of the reference line.

What is the minimum length of a skip weld segment?

Under AWS D1.1, each segment of an intermittent fillet weld must be at least 1½ in. [40 mm] long. Always confirm the minimum specified by the governing code on your project before laying out the joint.

When should skip welds not be used?

Avoid them on leak-tight and pressure-retaining joints, fatigue- or impact-loaded joints, and very short joints where segments make no sense. They are also unsuitable where corrosion could be trapped in unwelded gaps. When in doubt, ask the engineer.

Do I need the pitch dimension on both sides of the reference line?

For chain intermittent welds where both rows are identical, one clearly placed dimension pair is usually enough, but staggered welds must carry dimensions on both sides of the reference line so the offset is unambiguous. If only a length appears with no pitch, the weld is continuous.

What is the difference between a skip weld symbol and skip welding?

A skip weld symbol is a drawing instruction specifying an intermittent joint with gaps — it permanently reduces weld metal. Skip welding is a technique where the welder deposits short welds at spaced positions along the joint to spread heat, often while still producing a full-length weld overall.

How much weld metal and cost does an intermittent weld save?

Industry guidance puts the reduction at up to about 75 percent of weld metal (Lincoln Electric) and roughly 70 percent of weld volume (ESAB) in suitable applications. Savings come from filler wire, gas, labor, grinding, and less distortion correction.