Building codes are:

• A. Adopted by regions
• B. Adopted by the AHJ
• C. Mandated by the NFPA
• D. Mandated by the Uniform Building Codes

Answer: (B)

Building codes are adopted and enforced by the Authority Having Jurisdiction (AHJ), typically the local city, county, or state government. The AHJ decides which model code to adopt, which edition to use, and any local amendments, making that set of rules the enforceable code in that area. Organizations like NFPA publish model codes, but they don’t mandate them—that role belongs to the AHJ. The Uniform Building Code is an older model code that jurisdictions historically adopted or adapted, rather than something that mandates codes themselves. So the best description is that building codes are adopted by the AHJ.