As we discussed in our previous blog, there are three essential structural elements of pavement that we will review in our Asphalt Pavement Guide series; subgrade preparation, pavement thickness, and drainage.
When discussing these three elements we are going to speak in terms of residential asphalt pavement vs. commercial asphalt pavement – in other words, your driveways vs. your parking lot. In this blog, we will focus on asphalt thickness (review our previous blog in the series on subgrade preparation, and stay tuned for the final piece; drainage).
A good driveway starts with the ground (the subgrade), which must be smooth, firm, and evenly contoured.
- For your driveway, you should be using between 6-8” of properly compacted granular base aggregate on top of the subgrade.
- The thickness of a parking lot depends heavily on the amount and type of traffic of that specific lot.
- For standard commercial jobs, the dense-graded aggregate layer is typically about 8” thick.
- On top of the base, we typically recommend applying two 1.5” layers of asphalt. The first binder layer of 1.5” would be a thicker stone.
- For heavy duty traffic like, trucks, loading docks, or roadways, we recommend a 2” binder layer.
- Asphalt driveways need to be a minimum of 2” thick and are typically 3” (compacted).
- The finish course of a parking lot, following the binder layer, should be a smaller and smoother stone at 1.5” thick for a total of 3”.
- For heavy duty traffic like, trucks, loading docks, or roadways, we recommend a 2” finish layer on top of the 2” binder for a total of 4”.
Light Duty Parking Lots vs. Heavy Duty Parking Lots:
- For a full-depth light-duty commercial lot, it is recommended that a compacted layer about 4” thick of hot mix asphalt be applied on the subgrade.
- For full-depth heavy-duty commercial lots, it is recommended to apply a layer about 7.5” thick of hot mix asphalt on the subgrade.
- For a light-duty parking lot with an aggregate base, a hot mix asphalt layer of 3” thick on a 6” aggregate base is recommended.
- For a heavy-duty parking lot with an aggregate base, it is recommended to install a 6” thick hot mix asphalt layer on a 3” aggregate base layer.
If your driveway or parking lot is not paved to the proper thickness, your asphalt will likely begin to deteriorate prematurely. Subgrade preparations, base application and thickness, as well as asphalt thickness are extremely important in ensuring you are getting a good quality pavement with a long life. Proper drainage is the last essential element in making this determination, which we will discuss in our final piece of this series.