Permaculture design / Building placement

On modestly sloping land, if you have rectangular shaped buildings that are non-inhabited (storage, barn, etc), would it make sense to try and orient them lengthwise on contour? It would seem to make sense so they wouldn't get in the way of any future earth works, etc. Just thought I'd ask because I haven't seen this discussed anywhere.

What is the total land area?
how close to the edge of the property will the structures be?