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marc boulay 03-10-2010 11:01 AM

Igloo style oven
Hi everyone,

I want to build a 42 Pompeii oven, igloo shape insulated with 3" ceramic plus insulated concrete, no enclosure. This oven will be built inside a new sun room/extension to existing garage, this new place will be heated with a wood stove occasionally.

I would like to know if this is made for cold weather.

I am worried about the expansion, the way the hearth is constructed over the oven stand (structural slab and insulating layer).

Is this suitable for cold Canadian weather?

And is it easy to smooth out the insulated layer (vermiculite concrete) to receive the fire bricks?

Please help,


eprante 03-10-2010 01:30 PM

Re: Igloo style oven
there are many ovens in the north that have held up very well. See the link below. The vermicrete is weird but easy to work with. Search through the photo gallery and you can find pictures of ovens in all stages.

Good luck,


PhotoPlog - Finished Ovens

dmun 03-10-2010 03:38 PM

Re: Igloo style oven
A mixture of sand and fireclay is put on top of the vermiculite layer to smooth it out for the floor. This can either be mixed with water and applied with a notched trowel, or put on dry, the floor laid, and when you're satisfied with the level, then you wet the floor to set it.

There are some complications to building an oven inside your house, mostly having to do with building code. The oven will have to be built to masonry fireplace standards, and have a proper flue. You may not be able to share a flue with your woodstove. This all depends on how many hoops your building inspector will make you jump through. Building departments tend to be more rigorous in more populated areas.

marc boulay 03-11-2010 06:31 AM

Re: Igloo style oven

so my main question is if the oven is well insulated 3" ceramic and insulated concrete and all the needed stuco over it is there a need to have an insulated enclosure?
This oven will be inside a extension to my garage, and will have a saperate chimney.
Will the oven perform well without this enclosure? Will there be problems to attain high temps?
I really like to have the igloo shape.
Also, i have seen on other sites that the hearth is suspended on the block stand with rebar, insulation concrete poured first top by the structural concrete, making the hearth and stand seperated for expansion.
Is the difference/advantage with insulated concrete over the structural slab, like the Pompeii plans.

I am new to this and any help is greatly appreciated.


eprante 03-11-2010 06:58 AM

Re: Igloo style oven
the answer to your first question is that if your igloo is insulated according to the FB plans then there is no need for an enclosure for heat retention. The decision to build an enclosure or igloo style oven is personal choice based on aesthetics not function.

As to the second question why some other sites recommend placing the insulation layer under the structural layer; I dont understand the practice unless it is to add a ton of thermal mass to the floor of the oven. It seems to me that an oven with 4 inches of concrete under the cooking floor would take a very long time to heat up. You would use much more firewood with that design. If you want more thermal mass under the floor, you can add an additional layer of firebrick, much easier.

If you are intending to have the oven in an enclosed space, I would pay close attention to making your flue design large so that you don't have issues with the smoke exiting the front of the oven. Some people make the flue 1/2 a brick wide, others use a full brick width
good luck

dmun 03-11-2010 07:39 AM

Re: Igloo style oven
You understand that there is a solid dome, of firebrick or similar, covered by an insulation layer, either vermiculite concrete, or a refractory insulation blanket? Your description " 3" ceramic and insulated concrete " seems a little ambiguous to me. Once you've got the dome and insulation, the covering is strictly waterproofing and decoration.

I've also never understood the practice of suspending the entire mass of your oven by a few skinny horizontal rebar pieces. It doesn't allow for expansion - bare rebar expands more than concrete. It doesn't allow for a lack of thermal bridging - rebar conducts heat better than masonry. To say nothing of putting the insulation under the structural support. It seems like a bad idea all around.

Tscarborough 03-11-2010 08:21 AM

Re: Igloo style oven
"bare rebar expands more than concrete"

If this were true than modern reinforced concrete structures could not exist. As it is, concrete and rebar have almost exactly the same coefficient of thermal expansion. One of those lucky coincidences that allows us to build modern concrete structures.

marc boulay 03-11-2010 08:47 AM

Re: Igloo style oven

please see Pompeii plan, page 56, photo 13.3, FB blanket covered with wire and insulating concrete, it is hard to see how thick this insulating concrete is over the wire and blanket, so what would be considered sufficient thk?


dmun 03-11-2010 10:18 AM

Re: Igloo style oven
Can someone else cover this question? I don't have the PDF instructions at hand.

eprante 03-11-2010 11:10 AM

Re: Igloo style oven
The rule of thumb is 3 inches of ceramic blanket, or 4 inches of insulating concrete. Some people have used both (see sjmeff). If you are concerned about heating up your room form radiating heat off the dome, you could put an extra layer of perlcrete over the ceramic blanket or do 4-5 inches of blanket. You are in Canada so a little heat radiating off the dome probably isn't going to be a bad thing.

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