Old 04-17-2010, 09:35 AM
Derkp's Avatar
Join Date: Apr 2010
Location: Utah
Posts: 188
Default perlite insluation layer?


Thanks to all who have posted in response to my beginner questions that have probalby been answered before.

I am using firebrick for my floor and back wall that is 4.5 thick 3-7 inches wide and 18 inches long. We have wedge brick for the arches. Most will be a very tight fit, not large joints at all.
For now the oven size will be about 28X41 or so.

? How thick of concrete slab? on top of blocks?
? How thick of perlite/concrete insulation is reccomended to set the floor on?
? Reciepe for insulation layer?

I have also saw block stands that mortared and ones that are just dry stacked with the slab poured across the top. Does that work well? It makes me nervous with no mortar.

I noticed a block stand with cement board on top and then a insulation layer the shape of the cooking chamber and then formed up to enclose the insulation layer just under the surface of the slab, oven floor on top of that.
Good? Bad? Idea?

My father was a machinest, a little of the perfection overkill seeped into my genes makes it hard to decide on a design.

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Old 05-02-2010, 07:11 PM
Join Date: Jan 2010
Location: NYC
Posts: 27
Default Re: perlite insluation layer?

Hi! Derkp, To answer your question about the thickness of the top slab: 4 inches will be enough with #5 (1/2") reebar 12" on center. The thickness of the insulation layer should be 4" minimum if using the perlite/portland mixture. You could use insulation board but a 3 to 1 perlite,vermiculite/portland mixture will work just as well and is a lot cheaper. Allow at least seven days curing time for each stage (bottom slab, top slab, insulation slab). A base built with dry stacked blocks will have the corners and every other core filled with concrete and reebar. This will make a very strong base. For the bottom slab you might want find out if you have to worry about frost heave, and if so how deep the footing should be to get below the frostline in your area. If a footing is not required I would use at least 6" of crushed stone under the bottom slab which should be same as the top one. I hope this will help you and if anyone has more to add please fell free to do so.

Last edited by Ilfornaio; 05-02-2010 at 07:22 PM.
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