Roof Trusses and exterior dimensions

[rjesup]

If I want to use 'standard' roof trusses of 24'/30'/36', for efficiency, what dimension do I need to use for the width of the house below it in CA?  24' exterior measurement?  24' from the center of the walls?  Something else inbetween?  (Does CA include in the wall width the external siding, for example?  Which means 24' from outside of framing to outside of framing would be something like 24' 2+", depending on exterior sheathing, siding, any exterior insulation, firring, etc.   How exactly is this all handled in CA?

 

Thanks!   Trying to make my design be cost-efficient

[rlackore]

Typically, roof trusses span between the outside faces of the exterior wall framing (wall studs/plates).

 

In the Wall Specification dbx, the value reported in General>General>Thickness includes all the Wall Layers, regardless of whether they are Exterior Layers, Main Layers, or Interior Layers.

 

If you want to dimension to the outside face of the framing, define the wall with Wall Type Definitions>Wall Properties>Wall Settings>Dimension to Exterior of Layer set to the Main Layer component that defines the wall framing. Also, pay attention to the Dimension Defaults settings within the Default Set you are using.

[rjesup]

@rlackor You say "Wall Type Definitions>Wall Properties>Wall Settings>Dimension to Exterior of Layer " -- where do I find this?  I'm running Home Designer Suite 2022.   Thanks!  If it doesn't support this, should I try to make the exterior<->exterior distance 24" + 2(estimated sheathing and siding, perhaps 1"?) -> 24'2"? 
Thanks again!

[rlackore]

I am unfamiliar with Home Designer Suite. If you are planning on using 24' manufactured trusses, then the out-to-out dimension between the exterior wall framing should be 24'. For purposes of truss design, 99% of the time you will ignore everything (sheathing, siding, etc.) beyond the outside face of the framing (wall studs).