What an "Authority Having Jurisdiction" Actually Decides

"Authority having jurisdiction," often shortened to AHJ, refers to whoever is legally responsible for enforcing the code in a given location — usually the local building department, sometimes a fire department or another agency depending on the requirement. The code text gives the rule, but the AHJ interprets how it applies to a specific site, building, or unusual condition the code doesn't spell out explicitly.

This is why two similar projects in different municipalities can get slightly different answers to the same question, and why "the code says" is sometimes only half the story. When a requirement is ambiguous or a proposed alternative solution is being considered, it's the AHJ's judgment call — which makes an early conversation with your local building department worth more than guessing.