Pole barn base?

[wedge40]

I've got the plans done, but need some info.
I have my area leveled and it's been that way through all the rain we've had this spring. Its Indiana clay and 99% of the area drains pretty quick when the rain stops. Usually within 24 hours it's dry on top and can run a 7000lb tractor over it and barely leave and marks.
I plan on putting a base of gravel, then plastic, then foam insulation, pex and rebar, and finally 5" of cement.

My main question is how much gravel do I need to put down for the base. I'm guessing 4"-6" before I pack it.


Wedge

 

[radman1]

Provided you have good drainage, seems like way overkill on the gravel. You have a great base already with the packed and seasoned clay. In my region (midwest) most guys would put down enough gravel or sand to just get everything level and uniform. Then pack/roll the gravel/sand smooth and firm.