What is the AHJ?

The authority having jurisdiction (AHJ) is the local agency or official — usually the building department — that adopts, interprets, and enforces the code where you build.

Codes are model documents until a state, county, or city adopts an edition and (often) amends it. The AHJ decides which edition applies, issues permits, and inspects the work.

Because adopted editions and local amendments vary, the same question can have a slightly different answer in two nearby towns — always confirm with your AHJ.