The inspector is incorrect about NMB (Romex) being prohibited in exterior walls of a dwelling. However, their statement about bathrooms being potentially wet locations has nuance. Let's break it down

Exterior Walls:
NMB is generally PERMITTED in interior spaces within exterior walls of a dwelling. The key is that the space within the wall cavity itself (between the insulation and the drywall, for example) is considered a dry location unless conditions indicate otherwise (like constant condensation or leaks). NEC 334.10(3)

"Type NM, Type NMC, and Type NMS cables shall be permitted to be used in one- and two-family dwellings, multifamily dwellings, and other structures..." There's no general prohibition against using it in exterior walls.

Exception

If the exterior wall is subject to damp or wet conditions inside the wall cavity (e.g., a history of leaks, consistently high humidity leading to condensation inside the wall), then NMB is NOT permitted. This is less common but possible.

Bathrooms



Bathrooms are NOT automatically classified as wet locations. This is where the nuance is. A bathroom is considered a damp location, unless specific conditions exist that make it a wet location. Wet Locations (NMB PROHIBITED)

Wet locations are defined as areas subject to saturation with water or other liquids. Examples would include: Directly above a bathtub or shower, IF the wiring is subject to direct splashing or spraying. In the immediate vicinity of a whirlpool tub where water is likely to accumulate. Any place subject to standing water or constant condensation.

Damp Locations (NMB GENERALLY PERMITTED)

Most of the rest of a typical bathroom, where it is not directly sprayed with water.

What is important is the area that the NMB is running in. The NMB can not be ran directly above the shower/tub or in a location that water might accumulate.

Why the Confusion? Inspectors often err on the side of caution. They are responsible for safety. Bathrooms can be tricky. It's easier for an inspector to initially flag it than to investigate the specific location of the wiring. Some older codes may have had stricter interpretations.

How to Handle This with the Inspector


Be polite and respectful. The inspector has the authority to make the call.2. Ask for Specific Code References

Politely ask the inspector to cite the specific section of the NEC (National Electrical Code) or local code that prohibits NMB in the specific locations in question. This will help you understand their reasoning.3.

Explain Your Understanding

If you believe the inspector is mistaken, calmly explain your understanding of the code, particularly NEC 334.10(3) for exterior walls and the definition of "wet" vs. "damp" locations.
4.

Provide Evidence

If the issue is with the exterior wall, explain how the wall is constructed and why you believe the wiring is in a dry location. If it is bathroom, describe where the NMB will be routed, and that it will be away from direct contact with water.5.

Offer Alternatives (If Necessary)

If the inspector remains unconvinced, be prepared to offer alternative wiring methods, such as: Running the NMB in conduit through the questionable area. Using a cable type approved for wet locations (e.g., UF - Underground Feeder cable). Relocating the wiring to a less problematic area.

Important Considerations



Local Codes ALWAYS Prevail

Local codes can be stricter than the NEC. Your inspector is enforcing the codes adopted by your jurisdiction.

Inspector's Interpretation

Even with the same code, inspectors can have different interpretations.

Safety First

If there is ANY doubt about the suitability of NMB in a particular location, it's always best to err on the side of safety and use an alternative wiring method.

In Summary:

The inspector is likely misinterpreting the code. NMB is generally permitted in exterior walls and in many areas of a bathroom. Focus on demonstrating that the wiring is in a dry* location in the exterior wall or damp in the bathroom (away from direct water spray).If the inspector persists in their interpretation, you can appeal their decision to a higher authority in the electrical inspection department. But try to resolve it amicably first through polite discussion and code references. Flag for review