Welding inspection to AWS D1.1 and CSA W59.
Two structural welding codes govern most fabricated steel in North America: AWS D1.1/D1.1M in the United States and CSA W59 in Canada. They cover the same ground — prequalified joints, welder qualification, visual acceptance criteria, NDE extent — but they are not interchangeable, and the Canadian certification regime around CSA W59 is stricter than most buyers expect. This guide sets out what a welding inspector verifies under each, the documents that must exist before the first arc, and the rejects that recur on almost every project.
AWS D1.1 and CSA W59 share most technical requirements, but CSA W59 is applied together with mandatory shop certification to CSA W47.1 administered by the Canadian Welding Bureau. A fabricator qualified only to AWS D1.1 is not automatically acceptable for Canadian structural work.
Most weld non-conformances are not exotic. They are undersized fillets, undocumented essential-variable changes, unqualified welders, missing NDE records and repairs performed without an approved repair procedure — all of which are caught by documentation review and visual inspection before any NDT is commissioned.
- 01Confirm which code governs before mobilising: AWS D1.1 (US) or CSA W59 with CSA W47.1 shop certification (Canada).
- 02Documentation review comes first — WPS/WPDS, PQR, welder qualification and NDE procedures are accepted before production welding.
- 03Visual inspection to code acceptance criteria finds the majority of rejects; NDT confirms what visual cannot see.
- 04Undersized and incorrectly profiled fillet welds remain the single most common reject on structural work.
- 05Repairs need an approved repair procedure and re-examination to the same extent as the original weld.
AWS D1.1 vs CSA W59 — what actually differs
The technical requirements overlap heavily. The certification regime around them does not.
| Area | AWS D1.1/D1.1M | CSA W59 |
|---|---|---|
| Jurisdiction | United States and international projects specifying AWS | Canada, referenced by CSA S16 and provincial building codes |
| Shop certification | Not required by the code itself; often specified by the owner | Mandatory certification to CSA W47.1 (Division 1, 2 or 3) by the CWB |
| Welder qualification | Qualified by the manufacturer/contractor to Clause 6 | Qualified and administered under the CSA W47.1 certification scheme |
| Procedure document | WPS supported by a PQR, or a prequalified WPS | WPDS supported by the shop's accepted welding procedure |
| Prequalified joints | Clause 5 prequalified joint details | Equivalent prequalified joint details in CSA W59 |
| Visual acceptance | Clause 8 tables, statically vs cyclically loaded | Equivalent clauses, statically vs cyclically loaded |
| Inspector qualification | AWS CWI or equivalent accepted by the engineer | CWB Level 2 inspector or CSA W178.2 certified inspector |
What the welding inspector verifies, stage by stage
Inspection is sequenced so documentation and set-up failures are caught before metal is deposited.
- Step 01Hold point
Before welding — documentation and qualification
Accept the WPS/WPDS and supporting PQR against the governing code, confirm welder and operator qualifications are current and cover the position, process, thickness and material group, verify shop certification (CSA W47.1 where applicable), and review NDE written procedures and technician certifications.
- Step 02Hold point
Fit-up inspection
Joint preparation, root opening, bevel angle, alignment and misalignment tolerance, cleanliness, tack weld quality and backing where specified — checked against the joint detail on the drawing and the prequalified detail in the code.
- Step 03Witness / surveillance
In-process monitoring
Essential variables against the WPS: process, consumable classification and storage, preheat and interpass temperature, travel and technique, interpass cleaning, and welder identity against the weld map.
- Step 04Hold point
Final visual inspection
Weld size and profile, undercut, overlap, cracks, porosity, arc strikes, spatter, craters and reinforcement, evaluated against the acceptance table for the applicable loading condition — statically or cyclically loaded.
- Step 05Witness / review
NDE extent and interpretation
Confirm the examination extent required by the code and specification, witness RT/UT/MT/PT as scheduled, and independently review results before they enter the quality record.
- Step 06Closure
Repair and records
Review the approved repair procedure, verify excavation and re-welding, re-examine to the same extent as the original weld, and close the non-conformance with evidence into the weld and NDE dossier.
The documents that must exist before the first arc
If any of these is missing or expired, welding has not been authorised — regardless of schedule pressure.
Where weld hold points sit inside the ITP
Weld and NDE hold points only work if they are written into the project ITP with acceptance criteria and sign-off authority attached.
The rejects that recur on almost every project
Ranked by how often they appear on structural steel work, not by severity.
Undersized fillet welds
Leg length or effective throat below the drawing call-out, usually from over-fast travel speed. Measured with a fillet gauge at multiple points, not eyeballed at one end.
Undercut beyond limits
Common on vertical and overhead runs at high current. Acceptance depends on depth, length and whether the member is statically or cyclically loaded.
Unqualified or expired welders
The welder on shift is not the welder on the qualification register, or continuity has lapsed. A documentation check, not a weld defect — and it invalidates the work.
Preheat and interpass not controlled
No temperature-indicating record on thick sections or high-carbon-equivalent material, risking hydrogen cracking that appears days after welding.
Consumable control failures
Low-hydrogen electrodes exposed beyond permitted time, unbaked, or a classification substituted without a WPS revision.
Arc strikes and craters outside the joint
Rejectable on cyclically loaded members and frequently missed because inspection focuses on the weld rather than the surrounding base metal.
Repairs without an approved procedure
Grinding and re-welding done informally, with no repair record and no re-examination — the defect disappears from view but not from the structure.
Missing or unlinked NDE records
Radiographs and UT reports that cannot be tied back to a specific weld number on the weld map, making the record indefensible at handover.
How independent weld inspection is deployed
On a typical fabrication package the inspection effort front-loads: a documentation review before mobilisation, a fit-up visit at the start of production, surveillance visits through the run at an agreed frequency, and a final visual and records review before release.
Independence matters most at the interpretation stage. Where the party performing NDT also judges the results, rejectable indications have a way of becoming acceptable ones. Our CWI-led welding and NDT inspection keeps the testing and the acceptance in separate hands.
CWI-led welding and NDT inspection
WPS/PQR and welder qualification review, visual weld inspection to AWS D1.1 or CSA W59, and independent RT, UT, PT and MT oversight on your fabrication and site work.
Questions we get on this topic
What is the difference between AWS D1.1 and CSA W59?
Technically they cover the same ground — prequalified joints, procedure and welder qualification, visual acceptance criteria and NDE. The practical difference is the certification regime: CSA W59 is applied in Canada alongside mandatory shop certification to CSA W47.1 administered by the Canadian Welding Bureau, whereas AWS D1.1 does not require third-party shop certification unless the owner specifies it.
Does an AWS D1.1 qualified fabricator satisfy CSA W59?
Not automatically. For Canadian structural steel work the shop normally needs current CSA W47.1 certification of the appropriate division, with a recognised welding supervisor and welders qualified under that scheme. Verify the certificate scope and expiry before award.
Who is qualified to perform welding inspection to these codes?
Under AWS D1.1 the inspector is typically an AWS Certified Welding Inspector or an individual otherwise accepted by the engineer. Under CSA W59 the inspector is normally certified under CSA W178.2 at the appropriate level. In both cases the specification may add requirements.
What documents must be in place before welding starts?
The WPS or WPDS with supporting PQR or prequalified status, current welder and operator qualifications, shop certification where applicable, consumable and material certificates, the weld map with NDE extent, NDT procedures with technician certification, an approved repair procedure, and the signed ITP.
What is the most common weld reject on structural steel?
Undersized fillet welds — leg length or effective throat below the drawing requirement, usually from excessive travel speed. It is also the easiest to find, provided the inspector gauges the weld at several points rather than sighting it.
How much NDT is required by the code?
The extent depends on the loading condition, joint type and what the contract documents specify. Codes set minimum examination for certain joints, and project specifications commonly increase it. The extent should be fixed in the ITP before fabrication, not negotiated after welding.
Fabrication starting to a welding code?
Send us the governing code, the weld scope and the shop location — we'll confirm the right inspector certification and mobilisation window within one business day.