How many inches deep to excavate for a driveway that parks cars?

[jedi1648]

I have a 23 yrs old asphalt driveway that needs to be replaced with interlocking bricks or pavers. I have received four different suggestions about how deep that I need to excavate, as follows:

"Driveways should be at least 6 inches deeper than the thickness of your brick. So if you are paving a driveway with 2 1/2-inch thick bricks, you need to dig a level hole that is 8 1/2 inches deep."

"For vehicular traffic, excavate 9 to 11 inches deep to allow for base material and 6 to 8 inches of gravel."

"... need to excavate 12+ inches deep for driveway that parks cars (7 inches deep for walkway). "

"We typically dig a 12” base under patio’s and walkways, and then 18”-24” deep for driveways in Ottawa. The weight of a car will destroy any interlock with an insufficient base installation and you will be doing the levelling again in 2-3 years."


My asphalt is well settled and solid, and therefore my initial thinking is not to excavate deep (say 12 inchese maximum), because the new gravel put on top of the base needs to be settled, or compacted very well. Otherwise, certain spots of the driveway where the car parks may sink over time.

[Maymybonneliveforever]

I installed Unilock pavers well over 20 years ago and only last year did it start to shift only because I power washed the pavers couple times and managed to remove the sand between the pavers which caused them to shift over the winter. I dug down approximately 18" since it was on a slight inclind so I viewed that as a poorly drained area, which left me with a 15 1/4" base. If I were do do another driveway, I would dig down at least 14" minimum so in my case I dug down at least 4" too much in my opinion. I believe Unilock states around 13" ()12" ganular base, 1" bedding course for driveways) in a poorly drained area, I compacted every 4".

You will get many different suggestions and unfortunately I don't have time to copy and past Unilock's spec' sheet but it will boil down to........."to each there own".

[Mr Nobody]

Unilock's tech guide:

http://www.unilock.com/default/linkservid/56EA14E6-1C25-1A51-FAE2B534A21FE2EC/showMeta/0/