Foam Roof Thickness

How thick should foam be on new flat roof residential construction in Phoenix?

Thank you.

I would think the R 30 would be normal everywhere. Used to be 4" ISO and believe it is now 5" to acheive. An average is probably good as I believe you would desire to slope the roof for drainage with a full taper.

I belive your res. roof deck haven"t concrite or cor. metal. So ,should be some space(dead-and) with some R? 8) In my area we have below 32"in w.time. For low-slope wood deck with space, i prefer install 1.5-2 inches ISO R-10-14 plys sometimes 1/2 perlite or cement board second course. For conctite,metal deck , min. dobble 1.5-2 inch ISO+ cover board. Check your tipe off roof deck, area code and calculate,what ins. you need, Perlite have R- 2.7/inch,ISO R-6/inch,xxl solution today we have

I was under the impression that the OP was asking about a spray foam roof.