I am looking at possibly building a much larger garage over top of my existing garage. The current garage has eight foot ceilings and the new garage will have 16 foot ceilings. I think the new garage would go over the ridge of my current garage. I want to do this so I don't have to find storage for the stuff in my current garage.

Anyhow, how would I use a rotary laser level to level the new footings with a building in the way? I am told it can be done, but my Google searches have failed me so far.