I've found it difficult to come up with concrete answers in NFPA with regard to 1 &2 Family Dwellings and attached garages. Chapter 24 is all but silent on attached garages (CO section speaks to it). Are they to be treated as incidental storage or a separated storage occupancies? Over and over we see 20 min doors being specced between dwellings and garages, but that indicates a 1/2 hr. fire barrier, not a 2 hr., and not no requirement? I understand the IRC addresses this (I'm not a user of IBC/IRC), but it seems to be lacking clarity in NFPA 101?