Hello. Hope all are being safe and well amid this COVID crisis!!
I currently have a 7' x 13' concrete cantina attached to the house in the backyard. I will be covering this with composite decking and extending it past the cantina further into the backyard another 6'. Given I live in Toronto, that portion will use 48' sono tube etc.
The question I'm wondering about is the sleepers for the decking over the existing concrete. I've done a bunch of research and have seen 2x4s sitting on top of 1/2" PVC blocks to keep the pt off the concrete as well as using flashing tape. The 2x4 would obviously be screwed to the concrete every 12" where the PVC blocks are. The sleepers will be situated perpendicular to the house so the water can run off under the decking.
However, would it not save a lot of time, effort, money and material by simply using (for example) PVC 3/4" x 3 1/2" PVC trim boards alone with the decking on top??
Since the PVC trim boards are non-compressible and rot resistant this removes a couple of prep steps. No flashing tape, no rotting wood.