Removing paving stones to lay a lawn
I plan on removing the paving stones in my back garden and replacing it with a lawn, in order to make a much more pleasant environment and encourage more biodiversity. I've lifted up one stone to investigate, and there is a lot of sand (presumably builder's sand) underneath. It's at least half a foot deep. Do I need to remove all of this and replace with topsoil in order for new turf to thrive? Or can I simply mix the topsoil I have with the sand, and lay the turf on that? I fear it's the former, but that might make the whole project untenable. Or can I lay topsoil on the sand without mixing it, and then lay turn onto that? Any advice would be hugely appreciated. I'm clearly a complete novice at this and can't seem to find much online.
Thanks in advance!