You can go as thin as 1/2" if you want. Either OSB or plywood will satisfy building code, but I'd check just in case. Or you can hang on a bit and Gary will be by to link you up to code info.What size of plywood should I use when framing? It's an exterior wall of a garage. I'll be putting up vinyl siding if that effects the size. OSB or plywood??
It would help if you stated where you live.
Personally I only use 3/4" exterior grade ply.