There are two types of joints in concrete driveway slabs, Expansion Joints and Control Crack Joints. Every concrete slab, inside (basements, garages, etc.) or outside (driveways, patios, entries, etc.) are required to have joints every eight feet horizontally and vertically.

Concrete Expansion Joints

Concrete xpansion joints provide space between concrete slabs as a buffer for expansion on hot days and contraction when it is cold. Usually these expansion joints are installed during the initial installation of the concrete and are made of wood or some soft material so they can move with the expansion and contraction of the concrete. These joints vary in size from half-inch to an inch in width and three to four inches in depth. A slab without expansion joints will crack which will reduce the life of the concrete slab. These joints will crack all the way to the bottom of the concrete. If they come open, water will be allowed to run under the bed of the slab, eroding it and creating voids which during harsh winter conditions can heave and cause major cracks and displacement in the concrete. Open joints can also be point of deterioration of the concrete because of the freeze-thaw effect.

Control Crack Concrete Expansion Joints

Control Crack Joints allow cracking in a controlled area as the slab settles with time. Usually these joints are cut into the slab after the concrete hardens. Control crack joints vary in size from one-eighth inch to one-quarter inch in width and half inch in depth. A slab without these joints will crack in random patterns which ruins the look of the concrete as well as allows for damage from water intrusion and freeze-thaw which will reduce the life of the slab. Both type of joints will accumulate dirt and debris, allow grass or weeds to grow, and allow water to filter under the slab, etc. Water under the slab accelerates the settling of the concrete slab creating uneven concrete surfaces and cracks. It is very important to keep joints in good repair. An annual inspection of joints should be on every homeowner’s to do list. And knowing the proper way to repair these joints is very important. Many people just fill them up with a concrete material. This is not an optimal solution as the concrete will not expand and contract but will crack.