How we build our lessons and practice questions
Every lesson and practice question on Contractors Classroom is grounded in California's current code books and CSLB's own materials. This page names those sources, explains how the text is produced and checked, and tells you how to report a mistake.
The sources we use
Lessons and questions are written only from the California and CSLB sources below, and an explanation shows the section it relies on.
- 2025 California Building Code (Title 24, Part 2) and 2025 California Residential Code (Part 2.5)
- 2025 California Plumbing Code (Part 5) and 2025 California Mechanical Code (Part 4)
- 2025 California Electrical Code (Part 3): the California amendments and tables as that book prints them
- 2025 California Energy Code (Part 6), Green Building Standards Code (Part 11) and Fire Code (Part 9)
- Cal/OSHA Title 8 construction and electrical safety orders, and OSHA 29 CFR 1926
- California Contractors License Law and Reference Book, 2026 edition (Business and Professions Code and CSLB regulations)
- CSLB's official study guides, one for each exam, and CSLB's examination FAQ
How a lesson or question is produced
Drafts are written with the help of software, working only from the books above. Software is a drafting tool, not a source: a rule or number is kept only if it can be found in the book it cites. Each draft is then reviewed against the code text before it is published, including the numbers in worked examples and quiz answers.
Lessons cite the section they rely on, for example "2025 CRC Table R602.3(1)" or "8 CCR §1541.1(c)(2)", so you can open the same page in the book.
How CSLB's study guides fit in
CSLB's study guide for each exam lists the topics, their approximate weights and the books the exam was written from. We use that list to decide what to cover. Some guides still name earlier code editions than the 2025 books; where they differ, our lessons cite the 2025 California text, and the guide for your exam remains CSLB's word on what is tested.
What we do not do
- We do not publish pass rates, testimonials or promises of a passing score.
- Practice questions are study aids. They are not the real exam, and CSLB does not endorse them.
- Lessons do not rely on web summaries, forums or memory for code rules. Blog articles that describe CSLB or exam-center procedures cite the official documents they were checked against.
Reporting a mistake
If something looks wrong, email support@contractorsclassroom.com with the page address (or the lesson and step) and the section you think says otherwise. We compare the report with the book, and confirmed errors are corrected.
When codes change
California adopts new code editions on a published cycle, and CSLB revises its study guides from time to time. When a new edition of a book we cite, or a new study guide, is published, we re-check the lessons and questions that rely on it and update the text and citations. Codes and CSLB procedures change, so check the current text before you rely on any detail.
See the lessons for yourself
Open the free preview for your trade and read the explanations and their citations. No sign-up is needed.
Independent exam preparation. Contractors Classroom is not affiliated with the Contractors State License Board, and no course can guarantee a passing result.