Duplex, roof over other unit (R317.2)

[COEngineeer]

Ok, so I have a duplex where one unit is taller than the other. Unit B has a roof that goes over Unit A about 2 ft. The building department rejected the permit and told us to follow R317.2.1 Continuity and R317.2.4 Structural Independence. Has anyone experienced this? R317.2.1 says that: The common wall for townhouses shall be continuous from the foundation to the underside of the roof sheating...
Does this mean the rafter cannot sit on the top plates? What happens if I have a sloped roof over the other unit? Can anyone help?

 

[twinnell]

I have only seen townhouses and duplexes with the trusses running parallel to the party wall. Not being supported by it.

 

[csd72]

This sound fairly typical.

It is probably a fire separation issue-if you have joists running over the wall then this can act as a path for fire into the cieling space.

If this is the case then solid timber blocking between may give enough charring width to prevent fire.