We've planned to build two bedrooms and a bath in our attic. Today I checked the attic floor for level and found it slopes about 4 inches over 40 feet, really not noticable without a level, though. The main floor is not level either. Can I build the attic addition now and level the entire house later without damage to the new attic addition when the house is leveled? This house has a crawl-space foundation and is about 80 years old.