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Concrete over existing concrete?

Q. I want a larger patio with a higher elevation than my existing patio and my question is: must I remove the smaller patio? Or can I pour over it?

A. This can be done if you can raise the elevation at least 5 inches. The desired thickness of residential concrete is at least 4 inches. When placing over existing concrete you need at least a 1 inch buffer of sand between the two slabs. If you can raise it at least 5 inches, then don't bother with taking out the existing concrete unless there is an issue with the ground settling underneath.

As far as making the patio bigger, you can make it as big as you want. My only suggestion is to place rebar where the new concrete extends past the existing slab. Because the subgrade changes at the edge of the existing patio, this is a good spot to crack and break. Place rebar every two feet to bridge it.