My wood frame garage (22' X 24') and the concrete slab it sits on are 35 years old. The garage is in excellent condition is solid and square. (I built it myself). The problem is the slab (Wisconsin winters). It has some wide cracks and has risen up in the middle so the bottom of the garage door cannot sit flat on the slab. Everywhere along the outside perimeter the concrete is flat and the bottom plate is straight and is in good condition. In the past week I've had six contractors give me estimates on replacing the slab. Two of them say the only proper way to replace the slab is to jack-up the garage and completely pull out all the original concrete. The other four say that because the building is solid and square that cutting the slab about 12" - 18" away from the plate and leaving the original 8" thick concrete under the slab should work fine. Of course they will drill holes in the old and use rebars to tie the old and new concrete together. They claim after 35 years of settling all settling should be over by now. The difference in cost between jacking the building up and cutting around the interior of the slab is substantial as you can imagine: in the neighborhood of $2,000. I can think of a lot of other things to do with $2,000 if the results are going to be close to the same. Don't get me wrong though I do want it done right. In addition, some of these experts claim that jacking-up the garage could cause it more harm than good and to complicate things even more, there is a 2 foot square cinderblock chimmney sitting on the slab! By-the-way, I am sixty years old and plan on remaining in this house for the foreseeable future. Thanks for any and all help!