My first attempt for 42" oven / changed to 36"

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Hi,
Just few questions for the next steps.
The hearth height is good enough if i make it 4inch (10cm)?
This hearth will be cement and sand,correct?

When the hearth will dry, i will make perlite-cement base, i plan to make it 8inch (20cm).
Which is your opinion?
Thanks

[Tonyp]

Re: My first attempt for 42" oven / changed to 36"

Hi George,

4" thick hearth with 1/2" rebar on 12" center should be fine. You want to use concrete though so include gravel.

8" thick insulating perlite/cement layer sounds great to me.

Tony

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Hi Tonyp,

Yesterday i finished the cement bricks construction.
I finished the construction at night

Ok i will make 4" hearth height.

When the hearth dry i plan to make the 8" frame for the perlite-cement layer.

My question is:
When the insulating layer dry, can i add more concrete around so all the height will be the same?(concrete and insulating layer)

Or to add insulating layer in all area and not only in the center?
I think this method will take less time than the first.

[Tonyp]

Re: My first attempt for 42" oven / changed to 36"

Hi Tonyp,


When the hearth dry i plan to make the 8" frame for the perlite-cement layer.

My question is:
When the insulating layer dry, can i add more concrete around so all the height will be the same?(concrete and insulating layer)

Or to add insulating layer in all area and not only in the center?
I think this method will take less time than the first.

You could do either as I have seen it done both ways. From my understanding the edges of the perlcrete are fairly fragile and crumble easily so you can either build up the regular concrete around the outer edge of the insulation. Or you can pour the perlcrete the full size as the concrete hearth and edge the perlcrete in a thin layer of mortar. It kind of depends on how you plan to finish the outside of the block/hearth/oven whether you would want the concrete to come up around the edge of the perlcrete or a thin mortar on the edge to protect it until the outside is finished, is enough.

[NCMan]

Re: My first attempt for 42" oven / changed to 36"

George....here's what I did. I made my perlcrete layer basically the same size as my hearth slab and it's worked out fine. Even if you were to come back and pour some concrete around it later, it would have no real strength and would most likely crack, etc. Plus, what need would it serve? All I would recommend is to leave your forms on the perlcrete slab for awhile, to minimize chipping corners or edges and to install a vapor barrier between the slabs. Also, if possible, let your perlcrete layer dry out a bit in the sun and wind, as any moisture still left in it once you install your hearth floor bricks will, for the most part, have to be dried out in drying fires. I let mine dry out for a week or so after removing the forms, to let some of the moisture evaporate. I made my perlcrete at a 1:8 ratio and it's worked fine. If you wanted to, you could pour the edge areas at perhaps a 1:6 or so to have more cement in it, but there really is no need to do that. As always......my 2?. Best of luck w/your build!!

[George_M]

Re: My first attempt for 42" oven / changed to 36"

I will think about your suggestions and i will decide what i will do.

Yesterday i bought woods for the frame and today i will start it.

CNMan i will not make a construction over the oven,so if i don't add concrete around the perclete layer,i think that will start chipping day after day.

Which size of perlite is good to buy?

Also the cement for the perclete must be for heat purposes or i can use common cement?

Thanks

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Some photos of my last progress.

[NCMan]

Re: My first attempt for 42" oven / changed to 36"

George......if you are not doing an enclosure, I can see where you may want to pour your concrete differently than the method I used. There are a few builders on here who inset their insulation layer into the concrete. Not sure, but maybe Greenman is one? I know there are others. His is one way to do what you need and maybe others can give you some ideas? There are a number of ways of doing it, I'm sure. As for the Perlite size, the bigger the better. And try not to chop it up any smaller when mixing it, if you are able. Regular Portland Cement works fine.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Today i prepared the irons.
Next step,i will make the concrete to fill the frame

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Until fill the frame with the concrete i prepare my next steps.
I read,but i don't remember where,that the oven opening must be 63% of the oven size.Is this correct?
Look at my drawing.

[NCMan]

Re: My first attempt for 42" oven / changed to 36"

Yes, the oven opening height should be close to 63% of the internal height of dome. The width does not matter much, but make it wide enough to get your food, etc. into. I built a 36" oven also and made mine 11.25" high and 18" wide, as an example.

[NCMan]

Re: My first attempt for 42" oven / changed to 36"

I just looked at your drawing and I think you misunderstood. It is the height that should be 63% of the dome height (not the width). So......18" internal height (assumed) x .63 = 11.34". The width is up to you, but I would only make it as wide as you have to have it.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

I mean for the width not for the height.
For my oven,22" width is good enough or need more?

Also where can i read about dome height and from what it depends?
Because i think that i missed something in the reading.

Edit:
http://www.fornobravo.com/forum/f6/6...nce-20920.html
In this topic discussed about 63% for the entrance widht.So the rule is for the width or for the height
I get lost now.

[NCMan]

Re: My first attempt for 42" oven / changed to 36"

George.......The rule is for the height of your oven entry door, not the width. The width is whatever you need it to be. Remember, the wider the opening, the more potential heat loss.

[GianniFocaccia]

Re: My first attempt for 42" oven / changed to 36"

There are a few builders on here who inset their insulation layer into the concrete

This approach worked well in protecting the insulation, which was 2" of fiber board on top of 3.5" of vermicrete. You will spend a fair number of hours climbing and leaning over your dome as you construct it.

Just make sure that your entryway design (flared vs not flared) and vent dimensions are configured before you pour your slab. Once it's poured you are bound to construct your oven to match it's dimensions.

HTH,

John