Concrete is poured into forms, or pieces of wood nailed or screwed together to hold the wet concrete in place as it dries. In driveways, you want to make sure that the concrete is 4Ē thick. If itís any less than that depth, the weight of cars, trucks boats or whatever sits on it will quickly crack the concrete because it structurally canít bear the weight of those vehicles. After the forms are set, itís a good idea to use sand to smooth the surface of the ground where you will pour the concrete. Sand helps smooth the soil so it doesnít shift as much thereby reducing the risk of the concrete cracking as the ground shifts underneath it.
Contractors also put down (over the sand), an interlocking mesh of metal bars called re-bar. From above it looks like a giant metal honeycomb. But this metal layer also gives the concrete strength. The re-bar is supported with ďchairsĒ, little mounts that hold the re-bar up in the air so that when the concrete is poured, the weight of the mixture doesnít force it to the ground. So the idea is that when the concrete is poured, it goes through and under the honeycomb of metal so that the re-bar is in the middle of the concrete as it sets up. This metal gives the concrete much more strength than if it was poured solely over sand.
There is some debate about whether to attach driveways to foundations with re-bar. We recommend that you have the contractor drill holes into the foundation of the house at the garage, then insert re-bar rods into the foundation, attach them to the re-bar in the driveway and then pour the concrete. This way the driveway is attached to the house so that it is stronger and less likely to shift or rise or drop above the level of the garage over time.
Finally, what should you choose: concrete or asphalt for your driveway? It depends mainly on what climate you reside year round. In extremely cold climates where there is a lot of snow and ice, asphalt might be a better choice. Thatís because putting down salt to melt ice or snow has a bad effect on concrete. Salt causes most concrete to chip or flake and deteriorate more quickly. Asphalt can handle the salt just fine.