I am searching for A technical explanation of why the direction of the floor joists is irrelevant to the roof rafters. A building inspector rejected my drawings because of this design.
As long as your rafters are properly supported, ie. with proper rafter ties to resist thrust or a proper ridge beam, what composes the floor shouldn't matter.
Your first post stated trusses, the second rafters. There is a bid difference. The trusses usually take care of the horizontal component of the loads. With Rafters and joist the joist are usually used to carry the horizontal component, but if they run perpendicular to the rafter another method of handling that component must be used.
Building Inspectors typically do not "approve" drawing content (Plan Reviewers,hopefully licensed engineers, do this). Inspectors usually ensure that content of the drawings get constructed properly. I agree with DaveAtkins.
As long as roof framing and floor framing are properly supported, directions can be either perpendicular or parallel. It is more "common" to have them parallel for reasons mentioned above.
Running the floor joists perpendicular to the roof is quite common. It can be a useful solution to equalise loads over all foundations to eliminate problems with differential settlement.
I agree with the prevoious posts that any horizontal thrust from rafters at roof level should be properly dealt with.
I believe the issue is that a load bearing band joist is not able to resist twisting if the joists are not attached to it. This is not an issue in any prescriptive code I have seen but I am interested in any structural engineer's opiniion.
By having the floor span in the opposite direction to the roof trusses, you may be causing the foundation loading to be similar on each side, face of the building which will minimize differential settlement and may cause differential settlement to be more uniform. This is good...
I agree. But does the bottom of the loaded band joist need to be braced laterally or not? Is the connection to the top plate sufficient to prevent rotation? Would blocking be needed?
If I understand your question properly, it is braced by the floor sheathing at the top and the nailer/top plate on top of the foundation/lower wall. The sheathing bracing is provided by attachment of the opposite ends to the nailer/top plate. It shouldn't move out of location whether the floor joists are framing into it or if the floor joists are parallel to it.
