I inted to lay decking over a tatty concrete area at side of house. What is
the minimum depth of joist to use? I want to keep the increase in floor
height to a minimum. Would I get away with something like 2 x 2 inch joists
laid on thin roof slates to raise and level them over the concrete like
this....

====================== deck board
[ ] 16in [ ] 16in [ ] 2 inch joists
== == == slate / tile leveller
/////////////////////////////////////////////////// concrete base

or is this a recipe for a quick (though short) descent?

TIA
ZD