Builer didn't use green board in bathroom
I have found code books in our local library reference section. (Personally, I, as a homeowner, wouldn't buy one!) They aren't necessarily 'easy reading' though; maybe someone on this forum will print the chapter number(s) for you.
Once you find the appropriate code(s), maybe you can hold the builder accountable to fix the problem. I'd figure you'd at least want the waterproof stuff in the shower/bath area where water gets frequently splashed. (I guess maybe the builder thinks Michigan water isn't wet?)
Makes one wonder also, (if green-rock is in fact "code") why city inspection would have 'passed' the problem. There sure are plenty of houses that get built and occupied, whether or not they'd theoretically "pass."
Good luck; let us know how it works out!
I'll check the library next time I'm there.
I doubt if I change it, a good sealer/primer and quality paint will go a long time before any damage occurs.
The reason the green board is almost never noticed is that the building inspector comes to check the framing and the insulation, and then the next inspection is generally for a final to obtain the Certificate of Occupancy. At his point in time the drywall has already been painted or covered with wallpaper, ceramic tile, etc. and he has no way to check it.
Green board should ALWAYS be used in wet areas such as bathrooms, laundry rooms, etc. whether ventilation is provided or not. It is a building code requirement it all locals, that I am familiar with, to provide an exhaust fan in the bathroom. This has nothing to do with using green board.
While green board is the standard for wet areas it may or may not be covered by your building code. If it is, I would file a complaint with your inspections department and also notify your builder that he was in violation of the code and demand he fix the problem and get it up to code. The warrantee should have no bearing on this item if the house was built contrary to the building code.
K2 is right about the Durarock and Hardibacker being far more water resistant than green board however these materials are meant as a backer for ceramic tile applications not slick finished painted or wallpapered areas. If you have ceramic tile shower stalls, the backer should be at the very least green board. (Even though green board is not adequate for these extremely wet areas it is often used and accepted in many areas.) Cement board like Hardibacker, Durarock, or Wonderboard are far superior in these locations.