Materials for Stucco Dome? Design Styles, Chimneys and Finish Discuss Materials for Stucco Dome? in the Pizza Oven Design and Installation forums; insulation board that is used under the hearth alone doesn't insulate that well. It gets very hot under my oven. ...

[ThisOldGarageNJ]

insulation board that is used under the hearth alone doesn't insulate that well. It gets very hot under my oven. I'll have to address that next time too.

How much board did you use ? how thick is your slab ? Is it possible your feeling heat from steam from the oven floor curing ?

Did the 2 bags cover the dome and walls?

I used 2 bags for the dome...

How much did this stuff penetrate the 1/2" hardware cloth?

I stuccoed over the vermicrete.. I used the hardware cloth under it. But Im sure the 1/2 inch hardware cloth will be fine as the SBC is pretty thick and has fiberglass threads in it for structural strangth..

Vermicrete

goes over the blanket as an additional insulation, It is a mixture of portland cement and vermiculite, I used a 6-1 mix
6 parts of vermiculite and 1 part portland with just enough water to make it like oatmeal.. The vermicrete is highly recommended, you may have trouble getting up to and holding your pizza temps without it... or you will burn a crapload of wood to keep hot..

SBC

When using the SBC I added acrylic fortifier for waterproofing and Terra Cotta color was mixed right in... I used a sponge for my finish, sorry the pic isnt that good, i just went out and took it and its still dark here,,,

Aluminum Foil

This is usually not needed, some recommend against it,, I think in your case it may be a good idea if your planning on reclaiming your firebrick when you move, otherwise i dont think it is necessary.. THere is a theory that when Aluminum or copper foil is put on (shiny side facing the oven) it will reflect oven heat back in, There is also a structural use as a slip plane, which I honestly dont understand and Im hoping someone else can jump in here and explain,,,

Grout Sponge

I used it wet, kept a 5 gal bucket of clean water and rinsed it out every so often..

Hope that helps,, keep the questions coming as thats how we all learn
Cheers
Mark

[dmun]

Aluminum foil rots out in contact with the caustic portland products. In theory the shiny side could reflect heat back toward the oven, but in practice nothing but gold or platinum foil would stay shiny for long. I think the only thing it really does is trap moisture inside your oven and makes your curing period longer and more difficult.

I think it's one of those residual practices that someone once recommended, and keeps getting repeated. It's not actively harmful, like using sand for insulation, but I think it's pretty much useless.

[kebwi]

I've heard that the myths surrounding aluminum foil are complete bunk, that the shiny and dull side are completely identical and anyone could apply it in either orientation for any application with identical results. The difference in appearance between the two sides is simply a by-product of the manufacturing process, but it isn't, for example, a coating or anything like that. This is the claim made by someone who works in an aluminum foil factory.

What's the reference to the contrary, that one side behaves differently from the other for various applications?

[WaWaZat]

My slab consists of 1 1/2" insulation board on top of 1 1/2" thick 16"x16" patio pavers on top of a 4'x4' 3/16" steel plate. I believe it feels hotter on the bottom surface of the steel plate than it does outside my 1 1/2" blanket when the oven is fired. Of course the bottom of the steel plate is inside an enclosure.

So would using vermicrete outside my blanket be like taking care to to insulate & caulk your windows, then leaving the windows open?? The blanket I used is rated to reduce 750° temps down to 161° and 1000° to 193°. Is the vermicrete layer worth the time & expense in my case?

Just in case; is this vermicrete a mix that can be purchased at my local Home Depot?

[kebwi]

If I may make a polite suggestion, some of your questions would be -- at least in part -- alleviated by reading the free Pompeii directions. It discusses vermiculite and perlite based concrete...although I readily admit that I subsequently came to FB and asked a lot of questions about it myself.

My understanding is that you cannot buy vermicrete (as it is colloquially termed) mix. Instead you buy vermiculate or perlite (often in 4 cubic foot bags for reasons of economy) and mix it at some ratio (by volume) between 5:1 and 10:1 with Portland cement and some water. Having never made the stuff myself, I cannot offer advice from experience. I am merely restating what I've learned on FB so far.

BTW, it is frequently suggested that the Portland and water be mixed first, then the vermiculite added last (as opposed to blending the two dry ingredients and then adding water). I think there might also be a suggestion of wetting the vermiculite before adding it to the Portland slurry, but I am unsure what "wetting" means. Misted, drenched? I have no idea.

If I may ask, what kind of insulation board did you use? There are many options and I'm curious what path many people have taken.

[ThisOldGarageNJ]

My understanding is that you cannot buy vermicrete

You actually can buy it,, THey use it in building in ground swimming pools, I though could not tell you if the mixture is correct, but there are posts in the forum of people have used it...
Cheers
Mark

[WaWaZat]

Originally Posted by dmun

Aluminum foil rots out in contact with the caustic portland products.

What about galvanized steel? I ask because all the hardware cloth I've seen at the home centers are galvanized. Any reason I should not use that as my reinforcement layer for my concrete shell?

[ThisOldGarageNJ]

What about galvanized steel? I ask because all the hardware cloth I've seen at the home centers are galvanized. Any reason I should not use that as my reinforcement layer for my concrete shell?

Im not sure about rotting out, It may, My thought is that its used more as a form as well as holding down your insulation, It would be nard to put your vermicrete directly to your insulation... So it helps provide shape and something for the vermicrete to stick to, Then Stucco or SBC on top of the vermicrete..
Cheers
Mark

[dmun]

What about galvanized steel? I ask because all the hardware cloth I've seen at the home centers are galvanized. Any reason I should not use that as my reinforcement layer for my concrete shell?

Zinc is an entirely different metal than aluminum. The mesh that's designed to use with concrete, the expanded metal lath, is galvanized.
The linked article mentions acidity as a threat to galvanized steel; concrete is strongly alkaline.

[ThisOldGarageNJ]

Im not sure about rotting out, It may, My thought is that its used more as a form as well as holding down your insulation,

My point above that I may have missed is that if it does rot out, You have already gained the structural strength of your vermicrete and stucco, and it probably really wouldnt matter. I used the half inch galvanized hardware cloth,, I have about 5 months in,,, and I guess I will never be able to see if it does rot, But I have had 3-50 lb grandkids standing and climbing on my dome and between the vermicrete and Surface Bonding Cement,, still not a crack

So use it and feel food about it

Cheers
Mark