Your Needs
How thick should driveway asphalt be is entirely decided by the needs of your driveway. Whether you are installing a residential driveway or a commercial lot entirely dictates the recommended measurements of your asphalt driveway. As expected, the heavier usage, and the more heavy equipment you expect your driveway to have determines how thick should driveway asphalt be. If you plan on only using the driveway for residential uses and personal vehicles, the asphalt will not need to be as thick.
Regardless of what the purpose of your asphalt driveway is, the most important thing is having the proper soil underneath. Without good drainage soil and base materials, there will be lots of water build up which can be extremely damaging to asphalt driveways.
With the proper thickness and correct drainage materials, your asphalt driveway should be able to completely satisfy your needs.
Starting From the Bottom
The surface materials under the asphalt in your driveway are extremely important to ensure long term satisfaction. All asphalt driveways that are installed need proper drainage otherwise the driveway will suffer in the long term. The best material to use is a granular aggregate that allows for water to easily pass through. In a typical asphalt driveway, the thickness of this base aggregate can range form 6 to 8 inches in depth. Just like the thickness of the asphalt, the thickness of the aggregate entirely depends on the expect usage of the driveway.
The soil that is under the 6 to 8 inches of granular aggregate is also extremely important. The soil itself should be soil that naturally allows for good drainage. Example of good soil to have at the very bottom layer include gravel, rocks, and sand. These materials let water pass through with ease. Soil that is mostly loam and clay hold water at a high rate, making this soil not a good spot to put a driveway.
Residential Driveways
Residential driveways are for your own personal use, and should not be expected to regularly see heavy trucks and machinery pass through or park on them. Due to this the question of how thick should driveway asphalt be is much lower than it otherwise could be. For residential uses, 2 to 3 inches is typically recommended. If the driveway is just to house family vehicles and nothing more, just 2 inches of asphalt should be enough to hold cars without major damage. If you are expecting the occasional heavy truck, or other large piece of machinery such as a landscaping trailer or a boat, it is best to opt for 3 inches of thickness.
For residential driveways, it is also suggested to have 6 to 8 inches of base aggregate for optimal water drainage. This means in total from soil to surface of your asphalt driveway, it will be about 8-12 inches thick depending on your needs.
Commercial Driveways
How thick should driveway asphalt be is completely different for commercial driveways compared to residential. Unlike residential driveways, commercial driveways regularly see heavy equipment and trucks use their surface. These vehicles can range from work trucks, to trailers, to storage of heavy materials. To provide extra support, it is recommended to never go below 3 inches of asphalt thickness. Likewise, this means there must be more granular base aggregate to offer more support. The thickness of the aggregate should be a minimum of 8 inches. This means in total there should be 11 inches of total material above the surface, which is a full 3 inches more than how thick driveway asphalt should be residentially.
Consequences of Too Thin
When installed correctly for the intended uses, asphalt driveways actually spread the weight of the vehicle throughout a large portion of the surface. However, if the asphalt is too thin, this will allow vehicle tires to sink into the material. When the tire sinks, it then leaves an impression in the below surface materials. Creating this indent in the underneath material will allow there to now be space between the asphalt and granular aggregate. This separation then allows cracks and holes to form more rapidly. Once a crack or a hole is formed in asphalt, it is nearly impossible to stop the damage from spreading. Especially in cold months, if water gets into these holes and cracks, it can then freeze and expand which leads to even more cracks.
