Adjoining Historic Buildings

We are working to restore two commercial/residential historic buildings with the intent of achieving LEED certification. The buildings share an adjoining wall and staircase and share a tax parcel. One building is fully vacant and in need of major restoration, the other is partially vacant on the top floor but houses one apartment and a successful local business on the ground floor. Our goal is to achieve LEED certification for the paired buildings as a single unit for apartments. Since the buildings share a single main access stairway and are effectively legally already one building, are we within LEED's regulations to define them as a single building?