Often interlock is installed without a proper base. We know that in our climate, with lots of freeze-thaw periods, a patio needs at least eight to 10 inches of drainage gravel (base) to ensure that water isn’t being trapped under the stones. When water accumulates and then freezes, the whole patio can heave and shift. A driveway needs a base that is even deeper so that it can handle the freezing cycle, but also so that the weight of the car doesn’t compress the stones or the ice.
I also find that smaller paving stones are more easily moved by the weight of a car, allowing for more gaps, which always seem to fill with weeds.
So when Tracy Moore from TV’s Cityline asked me to interlock her driveway, I gave her a few alternative options to choose from.