Flying wings, of limited height and length, serve well when constructed integrally to abutments abeit reinforcing at the corner gets a bit crowded.
Once you reach a certain height and length threshold however, constructing an independent wingwall is preferred. Keep in mind that detached wings should be set back from the adjacent abutment stub to account for active pressure rotation.
Agree with Lobsta. With detached wingwalls, I usually detail some kind of deep architectural reveal so the wingwall movement relative to the abutment wall is not visibly apparant.
