Q.: When putting in a new driveway or sidewalk along the side of a house should I put rebars into the foundation? I have done so in the past but I have found that a crack forms parallel to the house a short distance beyond the ends of the rebars.
A.: Rebars should never be used in this fashion. Any driveway or sidewalk will inevitably be subject to changes in dimension caused by wetting and drying and by changes in temperature. The foundation is subject to less changes of this kind because it tends to stay drier and at a more uniform temperature. If the flatwork is tied to the foundation it will try to expand and contract but the foundation will try to prevent it from doing so. Some very large stresses will develop and cause a crack to form in exactly the position that you have experienced it. In addition, if there is any settlement under the slab, part of the slab will be supported by the rebars while the rest will not, and this condition also would lead to cracking of the kind you have experienced.