B1 vs B2: Which ICC Building Inspector Exam Should You Take First?

One of the most common questions I get from new inspectors is whether to start with the B1 (Residential Building Inspector) or the B2 (Commercial Building Inspector). Having passed both and supervised inspectors through each, here is my honest advice.

The Quick Answer

Start with the B1 unless your job specifically requires the B2 first. The B1 is a more approachable exam that builds foundational code navigation skills you will use on every ICC® exam after it.

Side-by-Side Comparison

The B1 exam has 60 questions and gives you 2 hours (120 minutes). It references the 2024 International Residential Code® (IRC). The ICC® exam fee is $250.

The B2 exam has 80 questions and gives you 3.5 hours (210 minutes). It references the 2021 International Building Code® (IBC). The ICC® exam fee is $320.

Both exams are open-book and multiple-choice.

Why the B1 Is Easier to Start With

Smaller code book. The International Residential Code® is a single volume covering residential construction. The International Building Code® is a larger, more complex code that covers every building type from small offices to high-rises and hospitals. Navigating a smaller code book while learning exam strategy is much more manageable.

More intuitive content. Most people have some familiarity with residential construction — they have lived in houses, maybe done some home improvement, or worked on residential job sites. Commercial construction concepts like fire-resistance ratings, high-rise provisions, and occupancy classification can feel abstract if you have never worked in that space.

Builds confidence. Passing the B1 gives you proven exam-taking skills. You learn how ICC writes questions, how to manage your time, and how your tabbing system works under real exam conditions. That confidence carries directly into the B2.

When to Start with the B2

There are some situations where the B2 makes more sense first. If your employer needs you on commercial job sites and the B2 is a job requirement, do not wait. Similarly, if you already have years of commercial construction experience and the IBC feels more familiar than the IRC, lean into that strength. If you are pursuing the CBO (Certified Building Official) designation, the B2 is one of the required certifications, so getting it done early starts the clock on that path.

The Study Time Difference

In my experience supervising inspectors through both exams, the B1 typically takes 4-6 weeks of focused study. The B2 typically takes 6-10 weeks. These timelines assume you are using a structured study plan and putting in at least an hour a day.

If you are studying for both, I recommend taking the B1 first, then starting B2 prep within a week of passing. The momentum and skills transfer directly.

My Recommended Order for New Inspectors

For someone starting from scratch who wants to build a full set of ICC® certifications, here is the order I recommend:

Start with the B1 (Residential Building Inspector) to learn the exam process. Then take the B2 (Commercial Building Inspector) while your study habits are strong. From there, add your trade-specific certifications — E1 or E2 for electrical, M1 for mechanical, P1 for plumbing — based on what your job requires. If you are pursuing CBO, add BC (Building Codes and Standards) and MM (Management Module) after the B2.

The Bottom Line

The B1 is the better starting point for most people. It is less expensive, uses a smaller code book, and builds the exam skills you need for everything that follows. The B2 is a harder exam, but it is very passable with proper preparation — especially if you have already learned the process on the B1.

Both exams are included in Building Code Academy along with 8 other ICC® certification exams. Each exam comes with study guides, practice tests, audio cram sessions, flashcards, tabbing guides, and more — all for $10/month.

Disclosure: This post was written by Levi Mittag, founder of Building Code Academy.

ICC®, International Building Code®, International Residential Code®, and related certification names are registered trademarks of the International Code Council, Inc. Building Code Academy is an independent study resource and is not affiliated with, endorsed by, or sponsored by the International Code Council.