The guy who is remodeling my bathroom put Wonderboard on the bare studs of the walls and then put drywall over the Wonderboard. Shouldn't there have been some kind of a vapor barrier or tar paper? I think this guy has no idea what he is doing.

I've seen vapor barriers on walls in bathrooms, but it's incredibly rare that you see it. Most builders do not utilize a barrier of any kind.

I'm more curious about the drywall over wonderboard. If by wonderboard, you mean tile backer board, I can't imagine why you would install drywall over it. It's intended to be a surface to mount tile to.

Thanks,
Json

Yea that is really odd, the backer board is just for tile, and drywall doesn't go over that at anytime, in fact I don't know of a reason you'd ever want to or need to do that, as for a vapor barrier I use 4 mili plastic. What was his reason for doing that?

Both Glavine and Json make good points but you already knew your installer was a bit off. Wonderboard or any tile backer board like Hardiebacker does not get drywall on top, they are tile ready. The only vapor barrier you should have is on your insulation. Never have two vapor barriers in the same wall, it traps moisture between them.

The guy who is remodeling my bathroom put Wonderboard on the bare studs of the walls and then put drywall over the Wonderboard. Shouldn't there have been some kind of a vapor barrier or tar paper?? I think this guy has no idea what he is doing.
Because the idiot doesn't know what he's doing! That's why. He built my shower without a bladder pan and now is trying to convince me that he mixed the cement with something and now the cement is water-proof. Right.

Well the cement by itself is never water proof but hopefully the tile and the grout will hold back the water until your check clears. Don't let this guy back inside your house.