I'm having a concrete patio laid behind the house. How far below the top of the foundation does the top of the patio need to be in order to prevent water from coming into my basement. The original smaller patio was about 4 inches below the top of the foundation. The new one will be right at the level of the foundation. The contractor assures me it will be ok, but I'm not convinced.

Flickit

patio was not a problem 4" down why change it?

labman

Code calls for the ground level to be 8'' below the top of the foundation. To keep water out of the basement, it then needs to slope away from the house. If you make the patio the same height as the foundation it will stick up above the ground making mowing harder. It will also make access easier for termites, ants, and other wood eaters. A patio flush with the top of the foundation and going under the siding, makes a perfect place for termites to make an undetectable path into your house. No problem for your contractor.

If he doesn't know better, or care about that, what other corners may he cut? Maybe talk to another contractor.