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How Thick Should an Asphalt Driveway Be?

By Aurora LaJambre ; Updated September 21, 2017
The strength of an asphalt driveway depends on the gravel base beneath it.

An asphalt driveway is a practical, long-lasting choice for a home. Similar to concrete, asphalt is composed of sand and stones and liquid asphalt that binds the two together into a solid surface. The thickness of an asphalt driveway typically ranges from 2 to 4 inches, but the pavement's strength is determined by the stability of the subsoil and the depth of the gravel base beneath.

Subsoil

The dirt beneath an asphalt driveway can have a big impact on the stability and longevity of the driveway. Once the site is excavated, a compactor machine or hand tamper must be used over the entire surface to compact the dirt down to force out air pockets and underground moisture. If your yard has sandy or clay soil, plan to lay geotextile fabric over the dirt bottom to prevent rocks in the base from sinking into the dirt.

Gravel Foundation

The gravel foundation provides asphalt with the support it needs to endure the daily stress of heavy weight loads. Gravel also provides a flexible buffer that can expand and contract when the ground freezes, preventing cracks and other frost heave damage. The thickness of the gravel base for an asphalt driveway should be at least 8 inches. Plan to install the rocks in 4-inch layers and compact each layer. To prevent the edges of the asphalt from cracking or chipping, make the gravel base 6 inches wider than the asphalt pavement.

Asphalt Pavement

The thickness of an asphalt driveway is in part determined by the proportion of liquid asphalt, sand and aggregate in the asphalt mix. Spreading a 3-inch-thick layer of asphalt over the gravel base is thick enough to provide a smooth, solid surface for vehicles. After hot asphalt is spread over the surface, a roller machine compresses the mixture into a dense, uniform layer.

Sealing Asphalt

Applying sealer over asphalt will not noticeably raise the level of the asphalt, but it protects the pavement from fading and water damage. The key to successfully sealing asphalt is patience. Unlike other types of pavement, you should wait at least six months for asphalt to set before curing it. Once applied, asphalt sealer lasts for up to six years.

 

About the Author

 

Aurora LaJambre is a writer and editor living in Brooklyn, N.Y. For over five years she's covered topics in culture, lifestyle, travel, DIY design and green living for print and online media. Her publication credits include "WOW Women on Writing," "Six States" and Catalogs.com. She graduated from New York University in 2003 with a Bachelor of Fine Arts in creative writing.