Using Method B, I'm working on a three-story multi-tenant office bldg that includes Tenant Areas on each level. It is mostly a medical office building. The main circulation on each floor is comprised of a wide corridor that is both structural and fire-rated that connects the two stairwells. The bldg is unusual because the main entry is on the first floor which is technically a half floor above grade. The Lower Level is a half floor below grade. There is an ADA ramp in the back that leads to the first floor and there is an elevator with an exterior door that is on grade at the back of the building. While it can serve as a freight elevator, it is generally used much more as a passenger elevator so guests don't have to use the ramp or stairs. There is a central main passenger elevator and common restrooms in the typical central bldg core.

Our initial interpretation is that the main circulation corridors on first floor and lower level should be considered Bldg Service Area and on the Second floor (will be leased to one single tenant) is Base Building Circulation. Would that be correct? I'm confused because of the different levels above/below grade with all being accessible and rentable by tenants.