We did this. Not easily mind you! Ours was sitting on the ground. We dug down where the cellar used to be. Started moving cut logs underneath for support. Jack'd the house up and placed 4x6 beams underneath the house but on top of the log supports. Slow process... Kept doing this a bit at a time until the whole house was up in the air so we could dig the trench for the foundation. Our house was built in 3 sections and not really hooked together so as it went up, it went out. Not easy like I said, but it is very solid now. When it was time to dig the trench we invited friends and family over for a work party on a Memorial Day weekend. Fed everyone great food (cooked by Grannie) and a keg of beer. It was great fun and done in no time. The forms were done next and then poured. A lot of work... And we decided once was enough... We've since sold the house.