A building pad will cut the topography down or raise topography up to the elevation you need for cut and fill. The building pad tool does not allow for sloping pads yet. Here are a few tips for managing building pads.
1. Let's say your grade slopes up to the building and you want to show (in your elevations) exactly where the grade meets the building. Well, Revit will not create this line for you and there is no way to join the geometry of a toposurface to a wall to get the grade line to show. So, you'll have to sketch a building pad along the perimeter of your building footprint to get the grade line at building footprint to show.
Hope these tips help you save hours of work trying to manage building pads.