Structural drawings communicate two separate things about a weld: what to build, and how to verify it. The welding symbol addresses the first — joint geometry, weld size, position, and finish. The inspection requirements address the second — what NDE method applies, what percentage of welds must be examined, and where on the joint. A CWI who can read weld geometry from a symbol but misses the NDE scope is working with half the information.
This article covers how NDE requirements appear on structural drawings, how to read them, and where the common ambiguities arise.
Welding symbols vs. NDE notation: two separate systems
AWS A2.4 (Standard Symbols for Welding, Brazing, and Nondestructive Examination) covers both welding symbols and NDE symbols, but they operate differently on a drawing.
A welding symbol consists of a reference line, an arrow pointing to the joint, and information above and below the reference line specifying the weld geometry. Arrow-side information goes below the line; other-side information goes above it. The "tail" at the end of the reference line, when shown, carries supplementary information — typically a WPS reference number, a process abbreviation, or a special requirement.
An NDE symbol can appear in the tail of a welding symbol or as a separate symbol on the drawing. When NDE requirements apply to specific joints, engineers commonly add an NDE designation in the tail. When NDE requirements apply uniformly to an entire weld type or category, a general note is used instead.
On many structural drawings, you will see NDE specified in a combination of both: a general note saying "All CJP groove welds to receive 100% UT" and individual symbol tails calling out MT on specific fillet welds at high-stress locations.
Reading the weld symbol: establishing what you're inspecting
Before reading the NDE requirement, identify what the welding symbol is specifying. Common structural weld symbol elements:
Reference line and arrow. The reference line runs horizontally; the arrow bends to point at the joint. Arrow-side = the side the arrow touches. Other-side = opposite.
Weld type symbol. Below or above the reference line: a groove (V, bevel, J, U) or fillet symbol. The groove angle, root opening, and root face dimensions are added as numbers around the basic symbol.
Weld size. For fillet welds, the leg size appears to the left of the symbol. For groove welds, the penetration depth or S-dimension appears in parentheses before the symbol.
Contour symbol. A straight line (flush), a convex arc, or a concave arc above the weld symbol indicates the required final surface profile. A finishing designator (G = grind, M = machine, C = chip) to the right of the contour symbol specifies the method.
Once you know the joint type and size, you know what the NDE must examine.
NDE designations in the symbol tail
When the NDE requirement is called out in the tail of the welding symbol, it typically appears as an abbreviation:
- RT — Radiographic Testing
- UT — Ultrasonic Testing
- MT — Magnetic Particle Testing
- PT — Penetrant Testing
- VT — Visual Testing (sometimes shown when a specific visual hold point is required beyond standard CWI observation)
A tail reading "UT-100%" means 100% of that weld is to be examined by UT. A tail reading "MT-S" (where S denotes spot) means spot MT at a defined frequency. The percentage or frequency is sometimes defined in the tail and sometimes defined in a project specification table referenced from the drawing.
If the tail is absent (shown as open), no special NDE beyond the code minimum applies. For structural steel under AWS D1.1:2025, the default NDE for CJP groove welds in tension members may include UT or RT at a rate specified by the contract documents.
Percent inspection and sampling selection
Partial inspection rates — 10%, 25%, 50% — come up frequently on structural drawings and in project specifications. Understanding what percentage means operationally matters as much as reading the notation.
Percentage applies to welds (joints), not linear inches. Ten percent UT on a shop drawing with 40 CJP groove welds means 4 of those welds are examined, not that 10% of the total weld length is covered.
Selection method must be defined. Random selection, owner selection, or engineer selection — the project ITP (Inspection and Test Plan) specifies who picks the joints. A CWI who selects only the most accessible welds is not fulfilling random sampling. If the ITP doesn't define the selection method, get it clarified in writing before NDE begins.
First-article or critical-joint bias. Some EORs require that the first weld made by each welder, or all welds at specific connection types (column splices, beam-to-column moment connections), are included in any partial sampling regardless of the overall percentage. The drawing or specification will state this if required.
For a more detailed breakdown of sampling rates by joint type and code requirement, NDE sampling rates under AWS D1.1 covers the code minimums and how contract requirements interact with them.
Arrow-side and other-side NDE scope
The same arrow-side/other-side convention that applies to the weld symbol applies to NDE. An NDE symbol placed below the reference line applies to the arrow side of the joint; above the reference line applies to the other side.
In practice, this matters most for:
Double-groove welds. A double-V or double-bevel groove weld has welds on both sides of the joint. NDE on both sides requires symbols on both sides of the reference line, or a general note covering both sides.
T-joint fillet welds with NDE. MT or PT on a fillet weld is typically called out on the arrow side (the side the fillet is on). If both sides of a T-joint have fillets, both sides need NDE symbols if both are to be examined.
CJP groove welds in butt joints. UT examination of a butt-joint CJP groove weld covers the full cross-section from one face. The arrow-side/other-side distinction matters less here, but when the drawing shows UT on one side only, the CWI should confirm whether scanning from both sides is required by the procedure.
When the drawing conflicts with the NDE method selection
A drawing may specify RT for a joint geometry where RT isn't practical — a T-joint fillet, or a thick-section CJP in a geometry that makes film placement impossible. Or it may specify UT where the geometry is too thin for reliable angle-beam examination.
The resolution is not to substitute at the inspector's discretion. The CWI documents the conflict and escalates to the EOR before examination begins. The EOR issues a clarification or deviation, and the NDE contractor proceeds under the revised requirement. A hold-point inspection plan that captures drawing review before NDE begins will catch these conflicts before they delay a project.
General notes vs. symbol-by-symbol scope
Many structural drawings specify NDE in a combination of general notes and individual symbol calls. This creates a layered system:
- A general note may say: "All CJP groove welds in tension members: 100% UT per AWS D1.1:2025."
- A general note may add: "Fillet welds at column base plates: 25% MT."
- Individual welding symbol tails may add requirements for specific connections above the general notes.
The CWI's job is to apply the most demanding requirement where they overlap. If a general note requires 25% UT on moment connection groove welds and an individual symbol tail requires 100% UT at a column-tree splice, the individual symbol requirement governs for that joint.
Connecting symbol scope to the inspection record
Every NDE examination must be documented — which joints were examined, by whom, by what method, and the result. The documentation trail runs from the drawing symbol through the NDE procedure to the examination report. When an audit packet is assembled for a project, the NDE report index should be traceable back to the drawing NDE callouts.
A CWI verifying completion should cross-reference the NDE contractor's report against the drawing NDE symbols — not just check that reports exist, but confirm the reports cover the joints the drawing required. Missing a required joint is a finding.
For a complete overview of NDE method options and when each method is appropriate for structural applications, NDE method selection for structural welds covers the technical basis for each. Shops generating digital audit packets that tie NDE reports to drawing symbols and WPS records can see the documentation workflow at wpswelding.com/pricing.
Rule library based on AWS D1.1:2025; verify against your governing edition.