I want to have my existing surface grades die or tie into the footprint of existing buildings as opposed to shooting across the footprint. ? som sort of 'clip' command ?
you could create a composite surface and paste your building footprints into your EG surface?
not a lot of work.
Copy your EG surface and open the tree of the copied surface, right clck edit choose paste. When prompted for which surface to paste, choose your building footprints.