It is important for constructors to recognize that a long-standing interpretation regarding partition walls in fire-rated construction has been re-evaluated and found wanting.
In general, construction requires that penetration of fire-rated assemblies has to be fire-stopped. However, it was long accepted that the top plate of demising walls can be butted to a joist or bottom chord of a truss, and fire-rated drywall butted to that assembly.
Unless the demising wall is similarly fire-rated, this practice represents an un-sealed penetration of a fire-rated assembly.
Acceptable alternatives are to construct the fire-separation and then install the demising walls:
Or, as noted, build the partition wall as a fire-rated assembly:
Code references:
9.10.5.1(1), 9.10.9.6(1)(a).
3.1.9.1, 3.6.4.2