What did your project turn out? Gratedex products are very expensive $10/sf for the underlayment. You need to add the stone/tiles on top of that.

Hi CinnaCracker

you have a couple of options whether these options may work for you or not depend on the type and size of that porcelain tile you are talking about

from what you mention the system you have inquired about requires the grate and the plastic pedestal, on top of that goes your porcelain tiles or pavers, we have installed these before

first of all there is a downside to that installation for your project although in some places it may be required for a installation in this format you can go ahead and save money by installing your deck with simply the pedestals, those pedestals work great with pavers no need for the grate and you will still achieve a level surface, thats why I would like to know what size and how strong is that tile you would like to install, not knowing this now I cannot suggest that the pedestal system will work for you yet

but thats one option, second option would be SILCA GRATE almost the same as those grates but you would intall them over a Pressure Treated Substructure it will slightly bring down your cost and the installation would be level and strong

again it all depends on your zone requirements and what the city will approve, as you might already know they limit the percentage of Flammable materials in a roof.

My company specialized in building Roof Top Decks in NY if you have further questions dont hesitate to contact us

Best,

Anthony Albino
City Decks New York

Here is a link that might be useful: City Decks New York