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Specifications for Concrete Driveways

By Dan Harkins ; Updated September 21, 2017
It may be hard to tell from the surface if your concrete driveway was built properly.

A concrete driveway leads to many garages, due to its strength, longevity and cost-effectiveness. It can last an average of 30 years or more without cracking or crumbling, as long the standard specifications are studied and followed during installation, which includes the insertion of expansion joints to compensate for changes in weather.

Thickness

According to the Portland Concrete Association, if your driveway isn't reinforced with a material such as rebar to form a gridded foundation, the common residential driveway should be at least 4 inches thick -- 5 inches thick if heavy vehicles like vans or SUVs will be parked there regularly. Though some communities regulate differently from the International Building Code, this and subsequent dimensions are common baselines.

Other Dimensions

Many communities differ in required widths for driveways, but a width of 8 feet for a single-car garage or 15 feet for a two-car arrangement is average. Other variations allow for a turnaround slab or an 8-foot width at the street that widens at a two-car (or more) garage. Check with local building officials to ensure you won't have to repour all the concrete because your municipality has stricter codes. Garage paving often requires local permitting, too.

Slope

Another factor that local building officials often scrutinize is the grading and uniform thickness of a concrete driveway, no matter if it's for residential or commercial purposes. In Portland, Oregon, for instance, a driveway must slope uniformly, without dipping or depressions, toward the street at an angle of at least 1 degree per foot. This ensures proper drainage during rainstorms and car washings.

General Construction

Though some communities don't require foundational support for concrete driveways, others do. This foundation of wire mesh, crushed gravel and, less often, rebar is commonly used by builders to prevent premature cracking. Joints are also part of a concrete driveway's specs, placed decoratively or in long utilitarian strips every 6 to 10 feet to give connected slabs of concrete an average of 1/2 to 1/4 inch of a gap to expand and contract. The standard for a concrete mix's compression strength, according to the American Standards for Testing and Materials code, should be 4,000 psi over 28 days.

 

About the Author

 

Dan Harkins has been a full-time journalist since 1997. Prior to working in the alternative press, he served as a staff writer and editor for daily publications such as the "St. Petersburg Times" and "Elyria Chronicle-Telegram." Harkins holds a Bachelor of Arts in journalism from the University of South Florida.