PVC Pipe Size for Shower Drain?

My house was built in 2003 in Winston-Salem, NC with the plumbing roughed in for a basement bathroom. The PVC pipe for the shower drain is 1 1/2" diameter. I was told by one plumber that it requires a 2" pipe but this is the pipe that was originally installed when the house was inspected at the time. Now I don't want to dig up the concrete floor to replace it if I don't have to. I know codes vary by jurisdiction and may have changed but before I call the permits office here can someone tell me if this might be true i.e., is this a requirement anywhere you know of?

drain

I do not know of any time when a 1 1/2" drain would have been approved for a shower. The inspector might have been told it was for a bathtub. But in any case, why would you want to spend money finishing that room and then wind up with a shower that does not drain properly, and becomes obstructed quite often? Not to mention possible problems snaking a line that size.

I looked at the drawing and it shows a tub/shower. Would a 1 1/2" pipe meet the code for that? I understand that a 2" would be better.

Yes, 1-1/2" is large enough for a tub-shower. That is because the tub offers an emergency reservoir in case of a clog. It's that shortcoming that a shower only does not offer.

drain

If your code does not specify a minimum 2" pipe for ANY underground drains, then 1 1/2" will pass.