Existing Concrete Patio -
Most concrete patios are 4" thick. And most likely, the concrete used to pour your patio slab was 2000-3000 psi. That would be an 8000-12000psi rating for a 3000lb wood-fired oven. We aren’t going to say yes or no… but it’s your call.
But if you do go ahead an build on an existing concrete patio…
Verify the actual thickness of the slab by digging down along the side of the slab. It needs to be close to 4" or more.
Verify that there ZERO utilities running under the area you want to place your oven by contacting your local Blue Stake or Utility service.
Drill a 3/4" hole into the existing concrete where the CENTER of each CORNER CINDERBLOCK will be when placed into position.
Drive an 18" or 24" piece of rebar or metal spike / metal stake through the holes and into the ground so just 2"-3" is sticking out of the TOP of the first layer of cinderblock.
Attach a 4" or 5" piece of rebar to the top of the spike.
Fill the cores or each corner cinderblock as you work upwards / adding cinderblock rows.
Existing Paver Patio -
As former contractors, we’ve seen well-built patios that could hold an elephant… and we’ve seen paver patios that would warp after the first rain. It really depends on the quality of the installation of the paver patio and how the sub-base was prepared.
Additionally, pavers are generally 2 1/2"H - Not the 4" concrete minimum we ask for.
Personally, having installed numerous paver projects, I WOULD NOT RECOMMEND building your oven on top of an existing paver patio. No sir!
Simply remove the pavers where you want your oven located, pour a proper 5.5" concrete base slab with rebar and then cover the base slab with the pavers you removed after you’ve built your oven base (if you chose to go that route).