Expensive top dressing gravel over 2" hardcore.

[epsilonGreedy]

I am thinking about improving the public facing side of my site for Christmas by finishing half the driveway with the top layer of gravel. The current surface is made from 2" clean limestone plus various build detritus that has accumulated over 2 years. The preferred top dressing is 10mm to 20mm Derby White which looks like Cotswold stone but is not as crumbly hence it should not turn to mush through frost damage.

 

The area is 100 m2 which equates to 3 to 4 tons for a thin coverage.

 

Given the expense of the dressing gravel and the relatively large voids between the larger 2" hardcore base would it make more sense to apply an intermediate layer of cheaper 1" limestone?

[Ferdinand]

I would apply an intermediate layer of weed membrane below the top layer, whatever you do underneath.