I want to add a gable fan in my garage to help cool it and help to let out the humidity in the winter. My garage doesn't have a high peak, so there is about 24" of height at the peak on the gable and about 12" between the 2x4 vertical supports. It would seem that I would need to cut out a support in order to fit in a fan. Is this correct and what is the proper way to support the roof if a 2x4 needs to be removed in order to fit in the fan? Would it make more sense to do a roof mounted fan instead?
I hate adding anything to the roof, it just gives a place to leak.
That truss you need to cut is non-structural. It’s made similar to a truss, so it will match the pitch, etc. Often carpenters will build a wall to match the pitch.
Therefore, yes, you can cut into that wall, cut through the middle 2x4 web (flat stud) and install a vent. (Make sure you don’t cut the roof joists.) However, I’d add a 2x4 around the opening to stiffen the area where the vent will be installed.
However, I’d verify that that side of your house is not the windward side. (I’d prefer the leeward side.) Wind driven rain could push through the vent causing multiple problems.