This section will help you to finalize your design by helping you to better understand typical material thicknesses for your specific application. Please keep in mind, that these are simply general guidelines. Your best course of action is to contact us for a free estimate and consultation from one of our project managers.
The pavement system is made up of three distinct components – subgrade, subbase and Hot-Mix Asphalt.
In order to understand each component of the system, you may want to think of it like this – the subgrade is equivalent to the footer of a house, the subbase is equivalent to the foundation of a house, and the Hot Mix Asphalt (HMA) pavement is equivalent to the house itself. If the footer or foundation of your house is improperly installed, the entire system will fail. The same is true for your pavement system.
The first component is the subgrade. The subgrade is the underlying soil prepared to support a pavement structure of pavement system. When our project manager meets with you, he will determine the suitability of your existing subgrade.
The second component is the (stone) subbase. The (stone ) subbase is the layer immediately below the Hot Mix Asphalt (HMA), typically consisting of a course aggregate such as 2A or 2RC stone. This course is critical to the overall strength of the structure. When our project manager meets with you, he will determine the suitability of your existing (stone) subbase. Or, if one does not exist, he will make a recommendation for the type of stone to use and the thickness best suited for your specific application.
The third component is the Hot-Mix Asphalt (HMA) pavement. Hot-Mix Asphalt (HMA) pavement refers to the many different types of mixtures of aggregate and asphalt cement that are produced at an elevated temperature in an asphalt plant. Pavement designers specify different mixture types to satisfy different pavement performance demands and to accommodate variability in the nature and cost of available aggregates and asphalt cement supplies. It is sometimes referred to as macadam, blacktop or asphalt pavement. When our project manager meets with you, he will make a recommendation for the material type and the thickness best suited for your specific application.
Special Notes:
- Due to rising asphalt pavement material costs, some paving contractors are attempting to save their customers money by proposing to install a wearing course at a thickness of 1”. Beware of any contractor that proposes a wearing course thickness of less than 1.5” as this does not allow for proper compaction, which in turn, guarantees premature failure of the pavement system. Although this option appears cheaper, it will cost you considerably more as you are forced to replace your pavement much sooner than anticipated. For more information, please refer to our section below titled: Time Available for Compaction
- Please also beware of any paving contractor attempting to sell you more than what you need. Due to the current condition of the economy, some paving contractors are attempting to sell you more than what you need in order to create more work for themselves. One example of this is proposing a two layer system of a base course and a wearing course. The overwhelming majority of all driveways installed in this area over the last 50 years are single layer systems of 2” – 2.5” of wearing course.
As a reference, we have provided the following table. There are many variables to consider when properly designing your pavement structure, so we highly recommend contacting us to set up a free consultation and estimate.
Application Type |
(Stone) Subbase Type and Thickness* |
Base Course Type and Thickness* |
Wearing Course Type and Thickness* |
Minimum Use Driveway |
6” 2RC or 2A Stone |
Not Typically Used |
2” 9.5mm, ID-2 or ID-3 |
Standard Driveway |
6” 2RC or 2A Stone |
Not Typically Used |
2.5” – 3” 9.5mm, ID-2 or ID-3 |
Premium Driveway |
6” 2RC or 2A Stone |
2” – 2.5” 25mm or BCBC |
1.5” 9.5mm or ID-2 |
Standard Parking Lot |
6” – 8” 2RC or 2A Stone |
Not Typically Used |
2.5” – 3” 9.5mm or ID-2; 2.5” – 4” ID-3 |
Premium Parking Lot |
4” – 8” 2RC or 2A Stone |
2” – 4.5” 25mm or BCBC |
1.5” 9.5mm or ID-2 |
Street |
6” – 8” 2RC or 2A Stone |
3” – 4.5” 25mm or BCBC |
1.5” 9.5mm or ID-2 |
Sidewalk |
4” – 6” 2RC or 2A Stone |
0” – 2” 25mm or BCBC |
2” – 3” 9.5mm or ID-2 |
* All material thicknesses listed are fully compacted depths.
Time Available for Compaction refers to the time (in minutes) that a particular mix is at the right temperature range for efficient compaction. Compaction must be accomplished before the mat cools to a temperature below 175 degrees. If compaction is not completed before the mat cools to 175 degrees, the mat will have too many air voids and will fail prematurely.
Why are we sharing this information with you? Because there are some contractors that are placing wearing courses just 1” thick. Utilizing a software program called PaveCool version 2.4 (developed by the Minnesota Department of Transportation), we have included the following chart for your reference:
Time Available for Compaction*
Air & Surface Temperature |
1” Thickness |
1.5” Thickness |
60 Degrees |
9 Minutes |
17 Minutes |
70 Degrees |
10 Minutes |
19 Minutes |
80 Degrees |
11 Minutes |
21 Minutes |
* Assumes the following: clear & dry sky, wind speed of 5 mph, dry granular base, and material temperature of 300 degrees at delivery.
The PaveCool software warns that paving should not be completed when the Time Available for Compaction is 10 minutes or less, as it is impossible to achieve compaction in that time period. Any contractor that quotes you a mat thickness of 1” is selling a significantly inferior product that is guaranteed to fail prematurely.
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