CWI Part C: D1.1 or API 1104? Choosing your code

Why you get a choice

Part C is the code application exam, and AWS offers it on more than one code because inspectors work to different codes in different industries. D1.1 and API 1104 are two of the options, and AWS lists others for areas such as aluminum, bridges, railway equipment, aerospace, pressure piping and pressure vessels. Check AWS's current list when you apply, because editions and options get updated.

The exam shape is similar across codes: open book, scored against the five areas of qualification, fabrication, inspection, reports and records, and materials and design. What changes is the book you navigate. A candidate who knows D1.1 well isn't automatically fast in API 1104, and the reverse is true too.

Structural versus pipeline in plain terms

The two codes were built for different worlds.

• D1.1 covers structural welding of steel: building frames, bridges, supports, platforms. It deals with joint details, prequalified procedures, stud welding, fabrication rules, tubular and nontubular connections and inspection. Loads are often cyclic or static, and the code reflects that.
• API 1104 covers welding on pipelines that carry oil, gas and related products, mostly girth welds joining pipe sections in the field. It leans on procedure and welder qualification by test, and on inspection of the finished weld by radiography and other methods.

You see the difference in daily work. A structural inspector spends time with fit-up, joint prep, shop and field welds, shear studs and visual checks. A pipeline inspector spends time with line-up, root passes, weld testing in the field and the paperwork that follows. Neither list is better. They just need different books on your screen.

How to choose

Ask these four questions in order:

1. What does your employer inspect? Look at the contracts and the drawings you see most. The code named on them is the code you'll be asked about.
2. What will your next job want? Check job ads in the industry you're aiming for. Structural fabrication and erection ads tend to name D1.1. Pipeline ads tend to name API 1104.
3. What do you already know? Familiarity shortens your navigation time. If you've handled one code for years, start there.
4. What will you add later? You can pick up more codes once you're certified, so choose for now, not for every future job.

If you're unsure, the how to become a CWI guide covers the wider route and you can also ask your employer which code your site runs on.

Can you change it later?

Not within a retest period. If you fail Part C, the retest uses the same code as your original attempt, so choose carefully before the first sitting. The CWI retest rules cover that rule and the retest limits.

After you're certified, AWS sells code endorsements to existing CWIs, which is how many inspectors add a second code. Check AWS's page for the current endorsement list and fees. If you are still deciding whether to sit for the credential at all, the pay article shows how to weigh the cost against the jobs you want.

What changes in your study

The skill is the same, and the book is different. For either code:

• Learn the layout first: where qualification, fabrication, inspection and records live, using your own licensed copy.
• Reach each section by its number, because the on-screen code has word search switched off.
• Time your lookups, then read the provision and check any cross-reference before you answer.
• Keep a log of topic, location and time. Redo the slow ones.

Don't try to memorize the text. Memorizing wastes weeks and doesn't help with a question that gives you a new scenario. Navigation does.

Edition awareness matters as well. Study the edition your exam uses. For D1.1 in 2026, that's the 2025 edition, and the D1.1 edition guide explains which book to buy. For API 1104, check the edition AWS lists on its Part C page before you buy a copy.

A quick test before you commit

Imagine the next ten inspections on your calendar. Write down the code named on each set of drawings. If one code appears seven or eight times, you have your answer. If the list is mixed, choose the code that appears on the work you'd like to do more of, since certification should pull you toward better assignments, not just describe the ones you already have. A two-minute check like this settles most of the debate, and it beats choosing a code because a prep course happens to sell it.

Practice for the code you pick

Fillet Gauge's Part C drills are built on D1.1, so if you've chosen D1.1, you can start today. Run the D1.1 navigation drill and try the clause-finding items in the Part C D1.1 guide. Then take the free 10-question Part C check, which shows exactly which areas to study first and how fast you find the answer. Start the Part C check.

If you've chosen API 1104, the approach carries over: build the same lookup routine on your own copy of that code, and use the D1.1 drills to learn the habit of going to the clause number first.

FAQ

Which code should I choose?

Choose the code your work runs on. Structural steel points to D1.1 and pipeline work points to API 1104. When both could apply, pick the one your employer or next target job uses most.

Can I change the code after a failed Part C?

No. A Part C retest uses the same code as your original exam, so decide before your first attempt. See the retest rules.

Is the code on screen?

For Part C the code is typically an on-screen PDF at the test center with word search off, and AWS recommends practicing with the bookmarks. Your exam booking tells you what applies to your code, so check it before test day.

Do I need my own copy?

Yes, for studying. Use a licensed copy of the edition your exam uses. We give clause numbers and drills, never code text.