Insulation Base Strength

[Vivi88]

Hey guys,

I'm making some progress on my build and wanted to get some thoughts on the plan for my base/bench for the oven, which is as follows:

- Thick galvanised, reinforced steel for the bench
- Hebel PowerPanels (aerated cement sheeting) as the bench top
- 6:1 Perlite Cement mixture for the insulating floor at 10 cm width, with steel reinforcement in the middle, sitting on top of the Hebel. No reinforcement planned for the floor to secure to the hebel, other than the weight of the oven.
- Fire bricks on the insulating floor

A couple of questions which I haven't seen answered in previous threads:

- I've gotten the idea to use the perlite cement mixture as the insulating floor instead of calcium silicate boards as I've heard that this mixture should insulate just as well at a cheaper cost (provided the perlite concrete is thick enough). My question here is, I've seen this used as an alternative when people are using domes made of a perlite cement mixture too, which is relatively light. I have a castable dome which weighs close to 200kg. Would a 10cm thick perlite cement floor at 6:1 ratio be strong enough to support the weight of my dome, or will the floor eventually crumble under the stress of the weight?

- Should I be using a mortar to bond the dome onto the bricks and the bricks onto the insulating floor, or will a cement/ fine perlite mixture suffice?

[ddtwod]

I would love to see an answer to this question as well.

At the moment, I am planning on using a backer board on top of my existing half round brick table. I am supporting it with a column of cinder blocks in the middle and may add additional support with 2x4's. This is a table that I am "re-purposing". I am not sure if a standard Portland cement base with fire brick on top is ok, or if I need an additional layer of Perlite mix between my Portland slab and oven bricks. I know the odd shape is going to be a bit of a challenge design wise, but just so you know, I am planning on extending the support slab out front over the base to give me room for the entrance of the oven.

[UtahBeehiver]

I suggest you get the eplans for Forno Bravo and review thoroughly, it will answer may of the questions you pose, the plans are only a few bucks. With the dry stack landscaping bricks, is there any vertical rebar between courses to prevent lateral movement? You will need some type of insulation between the concrete hearth and the firebrick floor or the floor will act as a heat sink.