From the Architecture tab of the top ribbon select the “Wall” tool drop down box and pick “Wall: Architectural”.
Ensure the correct Exterior Wall Famil is selected from the drop-down box at the top of the Properties Side Panel.
Set the Location Line drop down box in the Properties Side Panel to “Core Face: Exterior”.
Model the Exterior Walls at each level of the building.
To ensure the orientation of these Walls are correct, model the walls by following the perimeter of the building outline so that the core is inside the building.
Make sure to split Walls between Conditioned and Unconditioned Typologies.
Note: Ensure that the same Exterior Wall does not continue through Conditioned and Unconditioned Typologies. Revit will automatically combine two colinear Walls. If manually modelling Walls right click on the end node of a Wall and click “Disallow Join” to prevent Walls combining.