How to Determine How Thick to Make Concrete Slabs

Choose 4 to 5 inches for the main slab of residential homes with a strength of 3,000 psi. In most locations, an additional footer is required. The footer is a 6-inch to 8-inch wide strip of concrete that goes around the outside perimeter of the slab and reaches below the normal frost line for the area.

Opt for 4 inches, minimum, of concrete for a garage slab that is not going to have large vehicles, such as oversize trucks or RVs parked on it. Concrete with a strength of 2,500 psi is recommended for normal size vehicles; when moving to larger vehicles, the strength of the concrete should be increased to 4,000 psi and thickened to a 6-inch slab. For any slab that must withstand the weight of vehicles, the concrete should be reinforced with fiber mesh or rebar rods.

Select a minimum of 4-inch thick concrete for driveways, with a strength of 4,000 psi. For regular traffic of heavier vehicles, opt for a 5-inch thickness for the concrete. Standard measurements of single vehicle driveways are 8 to 9 feet wide, while double lane driveways range from 15 to 18 feet.

Choose a 3 1/2-inch concrete thickness for sidewalks and residential patios. Thinner sections of concrete may crack or break under the pressure of consistent traffic. However, some cities require thicker concrete for sidewalks, particularly if they are near public spaces, so you should always contact your local building department for specific requirements.