Regarding modeling exterior walls i ve always just modeled it as one wall including interior finish to stud substrate and finish.
Exterior siding wall revit.
We can see the pattern in shaded hidden lines views but not in photorealistic rendering.
Nbs reference description.
We apply this revit pattern to the wall structure as the exterior finish.
This will give us result like this.
To show the siding wall pattern in photorealistic rendering.
Siding and exterior wall materials.
Wall 1 has an interior finish and stud and wall 2 has substrate and finish.
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But i keep on hearing from some folks that they model this as 2 separate walls.