Just because you don’t see it, doesn’t mean it’s not there.  If there is a stump within the preparation area for a building, it is always proper to remove the stump along with the major roots by excavating, not grinding.  Grinding works fine if you are ridding the lawn of an unsightly blemish without upsetting a large area; however, the process of grinding will most likely leave a large majority of the stump and many major roots to deteriorate over time.  This deterioration under a building will create a hollow area that may very well compromise the building perched above it.  The excavated area must be filled and compacted with the proper compactable material.