I am purchasing a home that has a sagging floor (one of its problems). It spans an area approximately 25 feet long, and 6 feet wide. the most prominent area is the full bathroom with the left side where the cabinet is, is about an inch and a half lower. Another half bathroom is behind this room and would be along the short edge of the cabinet. The floor has to be replaced in there do to a roof leak..... my question is... how many jacks would I need to fix this, I know that I would need at least one on either end but would two more be sufficient? and also.... to make new footers for new supports..... is it ok to use quick drying concrete? The house is empty at this point... and only has minor drywall cracks at the beginning and end of the sag.... also. the house has a crawlspace... I would guess that it is 30" tall in the crawl space, but will have more precise measurements later. the most notable area of sagging is around a 35 square foot area near the roof leak.... (In my best opinion, as this is not my field, I am a nurse). I feel that from what I can see, gutters not assembled properly are the major culprit as they are in the vicinity of the outside of the house where this problem is located . any help would be appreciated