I have built a complete apartment inside of an existing metal pole building. I framed the entire apt. with 2x6 lumber. I was told I had to use UF-B wiring through out the apt. for switches, receptacles, and light openings. Is this some new code??

It would help to know at the least the country... state and even city or county as local codes can vary.

What would be more interesting to know would be, who said this and what code or authority was referenced.

The pole structure is open floored? They may consider it to be a damp environment and NMC is not acceptable. According to code, UF can be used in place of NMC but not vice versa.

I guess we should also ask you to define or describe "complete apartment".

My guess is that the back of the wall is open to the pole structure.