Not saying it is right or wrong... but my neighbours built a very, very large deck over their old patio about a decade ago. Not how I would do it but... They used 2X6 joists/framing. They cut 4x4 posts up (say 6.5 inches) and just sat them on the old patio and bolted the deck framing to them with the framing an inch (give or take) off ground for "drainage". With decking and space below the 2X6 framing they are about 7.5 inches from ground level to surface. So far, no serious issues...
