NEC 90.4 · Homes and commercial

Who enforces the code and can approve alternatives

Your building department, which the code calls the authority having jurisdiction, interprets the NEC, approves equipment and materials, and can give written permission to waive a specific rule or accept an alternative method that achieves the same safety goals.

Flowchart of NEC enforcement: adopted by a state, county or city, enforced by the AHJ, which can interpret, approve, waive or allow alternatives in writing. — Special permission is the written consent of the AHJ, so get any waiver or alternative method approved in writing before the work is done. Diagram: Farmer Works Electric, free to share under CC BY 4.0 · Download PNG · How to credit

What the code requires

The NEC is written to be adopted into law by government bodies, usually a state, county or city. Once it is adopted, the enforcing official is what the code calls the authority having jurisdiction, or AHJ. For most jobs, that means your building department and your inspector.

Under 90.4(B), the AHJ interprets the rules, decides whether equipment and materials are approved, and grants the special permission that some rules call for. The code defines special permission as the written consent of the AHJ.

Under 90.4(C), the AHJ may waive a specific requirement or allow an alternative method, but only by special permission and only where the alternative achieves equivalent objectives by establishing and maintaining effective safety. Under 90.4(D), if the code requires a new product that is not yet available, the AHJ may accept products that comply with the most recent earlier edition that jurisdiction adopted.

In the 2023 edition, these powers are organized into lettered parts, (A) through (D). The reorganization did not add any new authority.

On the job

Get any waiver or alternative method approved in writing before the work is done. A verbal okay in the field is not the same as special permission, which the code defines as written consent.
If an inspector rejects work, ask which code section it violates. Mike Holt's commentary on this section says a rejection should cite the specific rule.