On Wed, 6 Jan 2021 21:15:02 +0000, Ethan Brown
wrote:

Hi Trader, do you think anchoring each joist would allow enough space between the joist and the slab for the water to escape? Cheers

I think I would use 1 1/2"Trex for the sleepers under the deck. They
won't rot any time soon. That isn't going to be at the Home Depot but
a real lumber yard will have it. Run them up and down the slope, not
across it so it can drain. If you can't find that stack a ribbed
5/4ths Trex on the bottom and put a standard 3/4" trex or even PT wood
ion top of that. Use some 1/4" hardware cloth at the bottom so water
can get out but rodent's can't get in.

another option;
If you are near the coast, a marine supplier can sell you rough sawn
0.8 CCA lumber that will outlast us all.