Concrete drive base - Adding concrete over concrete

[celts]

I have a short concrete parking space which slopes downwards (a foot down over eight feet) and is thinner at the height of the slope but supports a car.
If I wanted to level the driveway out can I add concrete over this base and would the additional concrete have to be a certain depth to support a vehicle regardless of the thickness of the original base.
If the amount I have to add is over a certain thickness I would not want to add that to the higher end of the base as this would raise it to high so should I break it up to a certain level and relay the top end or simply break it all up (which I'm not too keen to do if it's not necessary)

[Tony McC]

You can lay concrete over existing concrete, but you may need to prepare the existing to ensure a decent bond between new and old. As for minimum thicknbess, I'd suggest nowt less than 75mm assuming you use a fibre-reinforced mix, although it may be possible to reduce this to 50mm if the substrate is sound and you get a really good bond.