john cunningham
If the house is old (50 years plus) and the drive has possibly been there forever you would only need a few inches of vibrated mot 1 stone. If it's a new house with a made up drive ( you can see that the builder has built up the drive ) you may need as much as 300 / 500 mM of hard compacted stone ( m. O. T. 1 ) before laying blocks. Look at the drive now, has it shrunk anywhere, can you see any evidence of cracks. If in doubt go down to virgin soil, don't take the risk of a short cut it's not worth it. JC
