Forno Bravo Forum: The Wood-Fired Oven Community

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-   -   3" or 5" (http://www.fornobravo.com/forum/f6/3-5-a-19362.html)

GIANLUCA 05-13-2013 04:45 PM

3" or 5"
 
Has anybody had any issues with a full 4" thick hearth reinforced of course with rebar and fence I am using ceramic board so no insulating concrete layer Or just go with 5" to be on the safeside. Also has anybody had bad luck with the 80 lb bags of quickcreate premix for hearth?? Or is it ok to use it

mrchipster 05-13-2013 05:33 PM

Re: 3" or 5"
 
Quote:

Originally Posted by GIANLUCA (Post 152484)
Has anybody had any issues with a full 4" thick hearth reinforced of course with rebar and fence I am using ceramic board so no insulating concrete layer Or just go with 5" to be on the safeside. Also has anybody had bad luck with the 80 lb bags of quickcreate premix for hearth?? Or is it ok to use it

STOP RIGHT NOW --- WHAT YOU ARE CONSIDERING IS DANGEROUS.

Your hearth cannot be concrete it must be firebrick or similar. And if you are interested in not laying waste to significant forestland and taking tons of time to heat your oven the area under the entire oven should be well insulated. In addition the areas over and around the oven should also be well insulated.

A 4 inch with rebar structural layer is sufficient, but used as an oven floor it will potentially decompose and in an explosive manner. Quikcrete is fine for the structural layer but not in direct contact with the heat of the oven.

If you are going to use vermicrete for your insulating layer do not use quikcrete use Portland cement - no sand or gravel just pure cement powder and water with vermiculite or perlite.

Even if it does not explode it will self distruct due to the heat in very short order.

Download the oven plans from this site and read other posts regarding insulation. You will be glad you did.

Chip

stonecutter 05-13-2013 05:38 PM

Re: 3" or 5"
 
I think he means a structural slab.


Most of the ones I have done are 3.5". It only supports the weight of the oven, so a 4" reinforced slab is fine.

Bagged mix works too....just don't buy any that have been stored outside unless they are covered well.

Gulf 05-13-2013 05:47 PM

Re: 3" or 5"
 
Chip,
I misread it too the first time I read it. I think that he meant that he is not going to use a v/pcrete layer but is going to use "ceramic fiber board" for the insulation layer.
GIANLUCA,
A full four inches of concrete should be good to support your oven. I like the bag mix.
Edit: What Stonecutter said :)

mrchipster 05-13-2013 05:51 PM

Re: 3" or 5"
 
Quote:

Originally Posted by Gulf (Post 152491)
Chip,
I misread it too the first time I read it. I think that he meant that he is not going to use a v/pcrete layer but is going to use "ceramic fiber board" for the insulation layer.
GIANLUCA,
A full four inches of concrete should be good to support your oven.

Gulf, I hope that is true, but I thought I better be on the safe side, we both have read horror stories about bad designs. And his wording left me concerned. Sometimes people mean ceramic backer board ie cement board, wonder board, hardy backer..... And that would be a disaster.

Chip

GIANLUCA 05-14-2013 07:04 AM

Re: 3" or 5"
 
To be clear sorry!! This is the structural slab that holds the oven not the cooking floor lol!!! I was just hoping to get advise on how thick do most use 4 or 5" I will be using ceramic fiber board as an insulated layer not vermiculite and of course the firebrick on top for the cooking floor


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