Yes, the only section of the house that is NOT level is that one 5 foot section of the floor where the addition is. There are no cracks in the basement walls or floor or garage (the garage and a porch above it are the additions to the house). As I see it, and from looking at the joists in the basement, the builder didn't use the same subflooring as what is under the original house floor. All joints meet properly. This is why I can't figure out what they did to the house and what to do to fix it!