Floor perlite isulation proportion

[Zidbotev]

Hello, I build Pizza oven in Bulgaria and I follow Forno Bravo instructions. I read a lot and decide to use perlite for the floor isulation. Are the perlite and vermiculite the same thing? In our area I could not find vermiculite or FB boards. Is the 5/1 ratio perlite/cement corect, because we usualy use sand, cement and perlite for house floor isulation. If I use only perlite and cement should the content be strong enought to support the full size firebrick oven weight?

[UtahBeehiver]

Short answer yes perlite will work 5 or 6 to one ratio for the floor. According to this white paper, perlite actually is a little better thermalwise. How thick are you planning to make the floor, should be at least 4" at 5-1, more if you can. You still need a structural base under the perlite/cement insulation floor.

https://community.fornobravo.com/for...ite-insulation

[Zidbotev]

Thanks for the fast answer, I already made the structual base + sand and sea salt layer on top. This is for absorbing the moisture, from big temperature difference. I will try to make the isulation layert 4"+.

[Cubebuild]

I am about to start my perlite base. Was thinking about 4” but how thick do I need it to be to have the same insulation value as calcium silicate board?

[Vivi88]

I've heard 10cm is the equivalent of a regular calcium silicate board (of 2.5-5cm), but depends on the ratio you're using. I would say 6 to 1 perlite cement will have similar insulation properties, more perlite will be even better insulation but lower strength.

What type of oven are you putting on the base?

I'm actually doing my perlite cement base this weekend, but I'm worried about the strength of the mixture to be able to handle about 200-300kg pizza oven dome on top of it. I haven't been able to confirm how much a 6-1 perlite ratio will be able to withstand in terms of weight.

[UtahBeehiver]

Here is a table of the K values of p/vcrete. For insulation under the fire brick floor you should use 5 to 1 on the dome you can use 8-10 to 1. I would consider 4" 5 to 1 bare minimum for floor.

[Vivi88]

Thanks, what do the K values represent? I haven’t heard this term before. I do see psi values and they seem quite low considering regular concrete has psi of 2000+. My oven will weigh around 200-300kg, I’m hoping this is fine. Do you know if steel reinforcement is required in the insulation base? Or will this potentially cause cracking when the steel expands with heat?