How Thick Should an Asphalt Parking Lot Be?

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If you have property access that anticipates a lot of traffic, constructing a parking lot might be essential. In order to meet the demands of traffic that your parking lot will be receiving, one of the questions you might be wondering about is how thick the asphalt should be on your parking lot.

Generally, asphalt parking lots should be between two to three inches thick. This thickness is intended for areas that receive light-duty traffic. However, the asphalt should be thicker -between six and eight inches- if it is a heavy-duty parking lot, depending on the base layer thickness.

There are different variations as to how thick an asphalt parking lot should be. If you'd like to learn more, we've compiled the information you might need when considering the thickness of your parking lot.

Asphalt road roller with heavy vibration roller compactor press new hot asphalt on the roadway on a parking lot construction site, How Thick Should an Asphalt Parking Lot Be

Asphalt Parking Lot Thickness

A freshly paved & painted parking lot has everything but customers.

When considering the construction of a parking lot, it is important to know the daily amount of traffic and the number of cars that will be parking on it. This information is necessary to know in order for your contractor to know the right thickness to set on your parking lot.

For starters, asphalt pavement is characterized by layers of different materials with specific strengths and functions. It starts off with a soil subgrade on the very bottom, followed by an aggregate layer, an asphalt base layer, and an asphalt surface layer.

A parking lot is often built upon a foundation of soil subgrade and aggregate layer to create a load-carrying structure to your parking lot. When these layers have been sufficiently compacted, the asphalt base layer and the surface layer are added to complete the pavement structure.

To give a basic insight on the expected thickness of a parking lot, the vehicle types and weights should be taken into consideration. They are categorized into light-duty and heavy-duty parking lots.

Light-duty Parking Lot

A parking lot that gets light-duty traffic often gets less than 1,500 vehicles per day and primarily has passenger vehicles with less than 2% single-unit trucks.

  • a full-depth light-duty parking lot is recommended to have a compacted layer of about 4 inches of hot mix asphalt to be laid on top of the subgrade.
  • a light-duty parking lot with an aggregate base on the other hand, requires a 3-inch thick hot mix asphalt to be laid on top of 6 inches of aggregate base.

Heavy-duty Parking Lot

A heavy-duty traffic parking lot receives an average daily traffic flow of 3,000 to less than 24,000 vehicles per day. It also primarily carries passenger vehicles with less than 5% single-unit trucks and 3% of combination trucks.

  • a full-depth heavy-duty parking lot is recommended to have about a 7.5-inch thick layer of hot mix asphalt to be applied on the subgrade.
  • a heavy-duty parking lot with an aggregate base is recommended to have a 6-inch thick hot mix asphalt layer to be laid on top of a 3-inch aggregate base layer.

What Type of Asphalt Is Used For Parking Lots?

A picture of an empty parking lot with a building in the background.

There are different types of asphalt and the type used for a project is completely dependent on the purpose and the supporting layers of the ground to be worked on. The asphalts used on roads and highways vary depending on the traffic they receive, and asphalted parking lots are no different.

For asphalt parking lots, the type of asphalt that is widely used for this project is porous asphalt. This mixture has been widely used since the 1970s and is primarily used for parking lot construction.

This is because porous asphalt enables water to drain through the pavement. It also enhances storm water management and can improve the quality of groundwater. It is also a very cost-effective solution and can last for more than 20 years, with a probability of a few minor patches here and there.

Does Thicker Asphalt Last Longer?

New, empty parking lot with freshly painted lines.

There is certainly a science to how thick an asphalt layer should be used for a project. Contrary to what most people know, having a thick layer of asphalt for your project may be detrimental to its quality. This is because asphalt is built in layers so making it too thick beyond its recommendation may cause irreparable damage.

Unlike concrete which requires thickness to provide strength and weight resistance, asphalt is dependent on the layers on which it is built. What is more important for asphalt paving is the compaction of the subgrade because the asphalt surface's integrity depends on it.

An excessively thick asphalt may not be compacted properly and over time, cracks and depressions will appear and deteriorate the paving.

Is It Possible To Pave Asphalt Over Concrete?

Sometimes, a business owner may already have a concrete parking lot that they wish to upgrade with asphalt pavement. If you are in this situation you might be wondering if it is possible to pave asphalt over concrete, then the answer is yes.

Concrete is a great base for asphalt because it is already stable and it lets asphalt be fully compacted. However, while this is a benefit for those who already have a concrete parking lot, there are some considerations to think of.

Sometimes, a concrete base will crack at the expansion joints due to frost heaving or an unstable base layer underneath. When this happens, these concrete slabs move and it may damage the asphalt over time.

If you are looking to pave asphalt over concrete, you have to make sure that the concrete surface below is stable and has no expansion joint shifting to prevent crack damage.

Aside from this, because of the expansion joints and the cracks it may cause, hot and cold temperatures may also cause expansion and contraction on your asphalt. This requires regular maintenance of your asphalt parking lot with crack filling and seal coating to prevent water intrusion that can cause even further damage over time.

What Makes A Good Parking Lot?

A picture of an empty parking lot with a building in the background.

You've probably taken into consideration the quality of the asphalt pavement you are having for your parking lot, as well as the fundamental foundation of the layers beneath them. More often than not, other details for this construction will be glossed over by your contractor. But to add valuable information to your new project, here are some things to consider to ensure that you have a good parking lot.

Make sure that your parking lot space has an efficient layout that is easy to navigate for vehicles to enter and exit. Also, make sure that the sizing and spacing of the vehicles are sufficient for your space to ensure safety and ease of parking for your clients.

Provide safety measures for pedestrians

Pedestrian crossing on the road, Zebra traffic walk way.

Parking lots aren't just for vehicles, but also for those who are driving as well. Make sure that you have well-marked areas for pedestrians in your parking lot, as well as access ramps and parking spaces for those who need them.

Ensure good lighting

One of the things that some parking lots miss is good lighting. Ensure that light fixtures are available for the entire perimeter of your parking lot, as well as in between the parking rows. It provides safety and security to your parking lot.

Keep it cool

If it is possible, consider planting trees around the perimeter of your parking lot. Because asphalt tends to absorb heat more than concrete does, the addition of trees or shrubbery around can slightly cool the area by offering shade.

Looks matter

Always remember to maintain the quality of your parking lot by consistently sealing cracks and other fissures. It helps keep your asphalt parking lot in its best possible shape. You may also want to decorate the curb for drop-off as it adds additional appeal to your customers.

Final Thoughts

Empty parking lot at city center with blue sky

An asphalt parking lot receives a certain average of vehicles that pass through and park in it every day. If you are considering construction for a light-duty parking lot, the standard thickness for an asphalt layer is 2-3 inches, depending on the vehicle volume it will receive. It will vary depending on the need and your contractor should be able to help you determine the best thickness for your parking lot.

If you'd like to learn more about other paving solutions, we have a few articles that may interest you!

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