Although it is entirely legal to use trusses placed at 24" oc, most quality minded builders will not do so. Opting rather to place them at 16" intervals.
The reason is that although 24" on center is able to handle minimum loads as set by your building code, there is not economical savings by going 24 rather than 16" oc.
In fact. it can cost MORE to place trusses at 14" on center due to the fact one cannot sheath the trusses with 1/2 plywood nor can one hang 1/2" drywall underneath.
24" fiberglass insulation can cost more and the potential for roof sheathing sag and drywall sag remains a problem for all 24" on center framing.
I agree with your Dad.
You would be much better advised to frame at 16" oc with trusses most all the time.
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