Hearth Design Philosophy

[christo]

Re: Hearth Design Philosophy

That's how I did it and it works great for me!

Christo

[james]

Re: Hearth Design Philosophy

That sounds right to me. The structural concrete slab at the bottom, either 2" of FB Board or 4" of vermiculite concrete on top of that, and the cooking floor directly on top of that.

We have a good base of experience that 2" of FB Board will readily insulate a residential oven and you will retain all the heat in your oven and the bottom of the concrete won't even get warm.

Go for it.
James

[Dino_Pizza]

Re: Hearth Design Philosophy

bbell,
That is exactly how I will be doing mine next month. If you look at Christo's answer above, and click on his link to his second page on his thread, (message #12? or something) you can clearly see a picture of his 5 blocks high stand, a 4" or so pour of concrete on that and then the 2" FB board or insulation board product that the oven floor bricks sit on.
Have fun on the project!
-Dino.

[bbell]

Re: Hearth Design Philosophy

Dino, James and Christo,

My thanks toeac of you for the reply. Now waiting for a change in weather (above 32 deg. would be nice) so I can pour a slab.

Be well.
Bill

[kgmfq3]

Re: Hearth Design Philosophy

Quick question about the oven floor. Do you sit the walls of the dome onto the cooking floor or do you cut the floor round like Hendo did and have the walls rest on the FB or vermiculite concrete? It seems to me that the oven would be more efficient if the dome walls sat on the insulating layer and not directly on the cooking floor.

Jay

[dmun]

Re: Hearth Design Philosophy

Quick question about the oven floor. Do you sit the walls of the dome onto the cooking floor or do you cut the floor round like Hendo did and have the walls rest on the FB or vermiculite concrete? It seems to me that the oven would be more efficient if the dome walls sat on the insulating layer and not directly on the cooking floor.

Either way works fine. The dome-on-floor method is easier, using few or no cuts, and it's what I did. The cut-to-fit method is what's used for professional ovens in constant use, where they may need to replace a worn or chipped floor in a few years. I figure any worn brick will be in the center, not the edge and can be sucked out with a shop-vac, and replaced.

I think the efficiency is the same either way. Both methods allow you to completely surround your oven with insulation.

[Xabia Jim]

Re: Hearth Design Philosophy

The dome-on-floor method is easier, using few or no cuts, and it's what I did.

Picture your finished oven as one unit, not a separate floor and a dome.

Opt for easier, no one except you will know the difference when it's finished.

[jhobbs]

Re: Hearth Design Philosophy

When using the FB for the insulating floor does it need to be as large as the support slab or just big enough to cover the oven floor, I imagine that you need some are to absorb and reflect the heat.

[dmun]

Re: Hearth Design Philosophy

Your oven should be entirely surrounded with insulation. Having the board sticking out beyond the oven floor means less dome insulation that you would need to surround the unit than if you cut it exactly to fit under the dome.

[chirobuggy]

Re: Hearth Design Philosophy

Thanks to all for this great knowledge base. I think I'm close to starting the journey.

[ja50ny0ung]

Re: Hearth Design Philosophy

Hi all, I'm all new to the forum, I?ve been researching and following this great site, my build is a few weeks in and I?m just about ready to poor my hearth. The question troubling me is that of the hearth thickness, the Bravo plans state 3.5" thick and some members insist on 4" minimum, the way my build has panned out my hearth is only 3" at the edges but recessed in the centre by 1" giving a total of 4" for the majority of it. Should this be ok??

Thanks

[Dino_Pizza]

Re: Hearth Design Philosophy

Congratulations on starting! You're going to have great time building your oven and certainly using it when it's done.

Your hearth thickness: the 3"-4", is this just the concrete pour? Are you going to put 4" of vermiculite-concrete insulated mix on top of this or where going to use a rigid insulation board (1" or 2" glass-fiber board)?

Mine is 3.5" to 4" but I have a lot of steel rods in it too. You don't have earthquakes in the UK so you probably rarely use steel reinforcment in small things but...my opinion would be that I would have no problem with 3" if there was some steel in it. Since yours goes 3" to 4", I would think that would be fine.

By-the-way, all other opinions trump mine )-Cheers, Dino

[countryboy]

Re: Hearth Design Philosophy

What size oven are you building and what are the dimensions of the hearth? I.e., wondering how much weight you will put on the hearth and how far from the edges it will be...

[Dino_Pizza]

Re: Hearth Design Philosophy

Here is a drawing of what I did on mine:
It's a 42" oven, the concrete block base I did is 6 1/2' feet deep by about 6' wide. The width seemed about right for any 42" oven using glass fiber insulation (I used 3 layers of 'FB blanket') and I have a steel framed structure beyond that. I imagine if you do an igloo style (stucco or rendered exterior) it would be about the same.

I also have a row of concrete block thru the middle of the base stand to cut the 'wood' storage under it in half. This whole design of mine may have little to do with your design but I hope the oven dimensions help you out.



this is what it looks like:

[Kyle Dillehay]

Re: Hearth Design Philosophy

This is a very useful diagram Dino, thanks for posting. I am in the plannning stages of designing my own oven, what a great forum this is! Kyle