The
subgrade should be compacted and have an even thickness.
A standard driveway is 4" thick
you want 4" thick continuously, not a 3" to 4" varying thickness.
Many sites have expansive soils. In
these conditions, from 2" to 8" of crushed rock should
be used as subgrade material depending on the soils level
of expansiveness. If you have doubts about the soil characteristics
in your area, consult a soils engineer. |