Modular hearth for Casa2G

[rdelmendo]

Hi all-

First post, about to embark on first WFO with a Casa2G that I plan to install with an igloo mosaic finish on a metal stand. My plan is to weld 2" L angle as the frame with 1" L angle as the cross members and rebar on top of that going the other direction. Then pour a 4" hearth on top of this frame. The hearth could in theory then be placed on a welded metal stand.

So the questions to the experts on the forum:
- Is 4" enough for the hearth?
- Any guess on how heavy this will be? Should I pour the hearth with the frame on the stand already?
- Should/could it be vermicrete?
- Is the FB kit board fine to put directly on this hearth or should I add a second layer of something else?

Thanks in advance for the advice. I'll post pics as the project develops.

Cheers,

Ron

[dmun]

Re: Modular hearth for Casa2G

- Is 4" enough for the hearth?

Yes.

- Any guess on how heavy this will be?

Normal weight concrete -- a mixture or sand, cement, and stone gravel -- has an accepted density of 145 pounds per cubic foot. Divide by three for a four inch slab per square foot.

Should I pour the hearth with the frame on the stand already?

Yes. Lifting that big a slab is an unneeded and potentially hazardous rigging job.

- Should/could it be vermicrete?

No. Vermiculite or perlite concrete has no tensile strength.

- Is the FB kit board fine to put directly on this hearth or should I add a second layer of something else?

If your slab if flat, nothing else is needed. If not, a mixture of fireclay and sand can be used to level it. I placed my insblock19 boards in wet concrete with good results.

[james]

Re: Modular hearth for Casa2G

Hey Ron,

If you pour a traditional concrete hearth, and screed it reasonably well, you will be able to lay the FB Board directly on the concrete without anything to level it.

Think of it this way -- the concrete is 100% structural (it holds everything in place) and it does not provide insulation value. The FB Board is 100% insulation (it does a great job of blocking heat in the oven) and it does not provide any structural value.

It's easy!
James

[christianb]

Re: Modular hearth for Casa2G

Do you even need a concrete hearth? Why not just use a piece of plate steel.

[fxpose]

Re: Modular hearth for Casa2G

I originally liked the idea of using a steel plate for my build. What immediately turned me off on the idea were the cost of the plate stock and the additional cost of having it cut to a custom shape/size.
The concrete hearth I poured cost me at least 75% less.

George