I am considering foundation options in Portland Oregon for a home with 3 stories, the 3rd being in the attic. This is a D1 seismic zone in climate zone 4C. IRC says that the foundation wall must be at least the width of the supported wall. Does this mean the actual structural part of the supported wall (the 2×4 frame), or does it include all of the exterior foam inside and outside as well? If so, does the foundational have to be exactly centered on the whole upper wall? Does it apply only to the part of the wall below grade?

This is an 8″ monolithic foam wall with integral 2×4 light steel structural component (GigaHouse panels).  I will have about 3 inches of foam exterior to the steel studs covered with StuccoMax, and about 1 inch of foam interior to the steel studs covered with PlasterMax. It would be great to have the foundation wall start about 1″ inside the exterior foam of the upper wall so that I can run 1″ of foam down the exterior foundation wall to create a frost-protected foundation using R4.5 XPS. Can I do this? See attachment. 

Note this is a minimum concrete foundation without a slab based on what others have done. Feel free to comment on that as well. All suggestions welcome. Thanks in advance.