When labeling parcels and their contained building footprints, you can avoid placing the parcel label over the building footprint by using the Maplex Label Engine Avoid overlapping labeled polygons as if holes parameter. The building footprints can be labeled with a straight style that enables the label to follow possible longer trend lines of the feature without decreasing the size of the label. If the Try horizontal position first option is selected, the Maplex Label Engine first attempts to place the label horizontally before placing it at an angle within the building.
The image below shows the building footprints labeled with the Straight position and the Try horizontal position first option. The parcels are labeled using the Avoid overlapping labeled polygons as if holes parameter in the Regular style.