Asphalt is made of rock, sand and oil. The rock gives the asphalt strength, the sand keeps the surface smooth, and the oil holds it all together.

Total asphalt thickness depends on the anticipated load it will carry:

•	Driveways: 2 to 3 inches
•	Parking lots: 2 1/2 to 4 inches
•	Loading docks: 4 to 6 inches
•	Roadways: 3 to 6 inches
•	Heavy duty situations: 6 inches or more

Under the asphalt is aggregate base material which varies from 4 to 12 inches in depth. The base material is as important as the asphalt in terms of the surface stability. Two inches of additional gravel is approximately equivalent to one inch of additional mix in terms of total load carrying capacity. In some situations where the sub soils are wet or unstable as with clay, it is necessary to install pit-run, granular sand material, in order to properly stabilize the area prior to installing the base and mix. Geo-textile fabric may also be used under the base when the sub soils are suspect.

Drain tile is installed when underlying water is an issue. If this is NOT done, water freezes and may expand up to 10%. This freezing and expansion cycle can devastate asphalt surfaces.