Personally, I'd reconsider using OSB on the ceiling.
The reason guys use OSB is so they can attach stuff to the walls. Ceiling? You are just increasing your fire hazard.....or rather, adding fuel to the fire.
Is this an attached garage? If so, the wall between the garage and house MUST be 5/8" type X drywall.
Otherwise....1/2" on the walls is what I've seen most guys use.3/4" **** is going to be real heavy.
I used 7/16" OSB on the walls and ceiling for my detached
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