drive block paving

Ok lets say for instance your ground is clay and holds a lot of water you would need to excavate lower and install crushed concrete prior to sub base this will hold up better as no limestone and also aid drainage

As a rule of thumb most driveways only need 150 of Type 1 sub-base but when excavating you will see if the ground is soft, a good way of testing is the dig your heel into the ground or gentle push a steel bar in it will give you a indication of what we call the CBR value, if soft take out another 75mm Regards Peter.

You should also lay a geotextile membrane before you lay the base. This creates a barrier between the sub soil and base and at the same time helps to spread the weight of the base.