+1 for lightweight construction, probably 24" o.c. joists.
The problem is that the truss manufacturers sold the concept of the truss (and lam-beam and engineered I-ben) to the AHJ's (Authorities Having Jurisdiction, ie the cities and towns) and the agencies that compile the Codes basing the superior performance on non-fire behavior, which (admittedly) is 99.999 of the uses it will be found it. Add the savings in materials and labor and it seemed like a "win-win"... stronger materials with cost savings.
The problem is that the difference is so dramatic when exposed to fire conditions that lightweight construction bears little resemblance at all to traditional "stick" built construction. While stronger, the increase in strength allows for architects to specify fewer structural members; cost considerations means the architects will design exactly to capacity with no "over-engineering", reducing the ability for the other members to assume the load should one fail.
The result? A single engineered member fails... the other engineered members, weakened by heat and already at their maximum designed loads, cannot hold any more and buckle.
Floor, roof.... it's a killer.
Sorry - we now return you to the thread already in progress.