Q.: In a driveway 100 feet long how close together should expansion joints be located?
A.: Strictly speaking, these joints are control joints rather than expansion joints, because they are put in to accommodate the drying shrinkage that takes place after the concrete has cured. Normally the concrete does not expand to a size greater than its original length as cast. Control joints in driveways should be spaced at intervals about equal to the slab width, but drives wider than about 10 or 12 feet should have a longitudinal joint down the center. Also it may help to try to make the panels of the driveway approximately square.