Perlite doubles as finishing structure?

[BrickPizzaMA]

Hi everyone! I am fairly new to the forum and recently started my own oven. I had this idea: After I construct the oven, create a plywood form around the it and filling it with perlite concrete. Then I would scratch coat the surface and apply my finishing stone directly to the perlite concrete. The masonry supply shop I got my perlite from said it would be structurally sound, but I forgot to ask if there would be issues in the thermal properties of the oven (Square form on circular oven would cause some areas of insulation to be 5-6 inches thick, others 3-4). Has anyone tried this? Anyone had any issues? The reason I'm doubling the purpose of the perlite is to save cost on a metal stud structure.

Thanks!
-Rob

[Neil2]

Perlite is extremely porous, even scratch coated.

It can be covered with "water resistant" finishes but if you are going to build an enclosure I would consider conventional steel studs and a water proof wall/roof system.