What is the maximum height difference between concrete garage slab and the driveway slab?

Your concrete base has been laid and is flat, level and over-sized by 150mm(6in) to the external sizes of the proposed building.
The concrete floor must be of a minimum depth of 4in(100mm) although it is recommended that you excavate deeper perimeter toe-beams. The slab must also be 4in(100mm) above the surrounding area which includes the adjacent driveway, garden or path and a 1:10 ramp be concreted into place. For more information see http://www.4concretegarages.com/concrete_garage_single.asp#question10 http://www.4concretegarages.com/concrete_garage_single.asp#question3