I am renovating an 1870s house in MA and started by gutting a small
bedroom on the 2nd floor. After insulating, I plan to install blueboard
with veneer plaster. I have read DIY books, Building codes and these
discussion groups but I cant figure out whether I need 5/8" or 1/2"
blueboard. I guess it depends on local building codes and where the
room is located, but I am wondering what the rule of thumb is? 1/2"
blueboard is readily available, while I would need to go to a
commercial dealer to get 5/8". Which brings up another
question....does 1/2" blueboard/sheetrock plus the 1/8" veneer count as
the 5/8? Any thoughts would be appreciated.

Thanks

Joe