i have leveled 3 old houses that have pier and timber construction. it is not hard to do, just time consuming. find the highest point under the house, the area that has sunk the least. this is your standard. you must level the house to this pt. if you have no other reference point. connect a water/hose level to this point. drive double nails at 6' intervals along all the sills under the house. the nails hold the hose (and level) against the sill as you jack (I used 10 6-ton jacks along the lenght of the sills). the sill is level with your standard if the water on your standard is equal to the water on your jacking pt. you must have them level at the top edge of the sill, where your joists rest, since the sills may have unequal thicknesses. don't use the bottom of the sills as your water-level pt. with a 50 to 100 ft. hose, you can level both straight down a sill and also diagonally across the house. you can buy the clear hose water levels at Home depot.