A two family dwelling offers some breaks in fire separation requirements per section R317.1 of IRC2006 when compared to townhome requirements of of R317.2. The townhome section makes specific reference to continuity and exterior walls requirements of R302 because they are always considered seperate buildings. The two-family dwelling section makes no such reference leading me to believe that R302 is primarily directed at townhomes. Can we assume that a two family dwelling, even with a zero lot line (non condo/private ownership), is exempt from section R302 exterior walls? Probably not, but it does not seem to be well documented and it seems odd that arbitrary property lines affect life safety mandates. Thanks