Materials for Stucco Dome?

[WaWaZat]

Oven is cooking great and I'm finally ready to cover my approx 38" outside the insulation, refractory, dome oven so I can forever lose the blue tarp & cook throughout the snowy winter! I'd like to keep the igloo shape. I figured on using 1/2" hardware cloth for the stucco base coat based on suggestions in this forum. Exactly what to do for stucco is still up in the air.

I talked with a stucco manufacturer... Parex... RE what I'd need. They tell me to use their 4.5 ounce reinforcing mesh and their Armorwall 100 or 300 as a base coat. They also say that THIS IS NOT WATERPROOF. I'm told I would need another 3/32" coat of their Parflex with possibly another layer of reinforcing mesh of some sort, on top of the base coat to seal from water. Problem is finding this stuff in less than 50 lb pales.

So my questions are;
1) Is all the above necessary & in the best interest of my oven?
2) What techniques & materials do others here use for a water-tight, weather-proof dome?
3) How do I determine how much material is needed?

I have yet to come across anything in my reading that addresses making sure the stucco dome will be waterproof... so as to protect my expensive insulation blanket.

I intend on having the final layer colored a burnt orange. Suggestions?

Any tips, techniques and answers to my above questions are appreciated. It will be cold soon!

[Les]

Re: Materials for Stucco Dome?

You pretty much are going my route. If you dredge through my final posts, you can see how I accomplished the task. I used an acrylic product made by Dryvit - you can get it in any color you want. Being acrylic, it is probably as close to water proof you can get with an igloo shape. I built a 42 inch and bought 10 gallons. I think 5 would do it - I just sucked at shaping the stuff so I bought more. I have a butt load left over for touch up

Les...

[WaWaZat]

Re: Materials for Stucco Dome?

Les... you used this one product for the entire thickness of the shell? How many layers?

Do you recall the subject name of the thread you're talking about? Did you start it? Are all the details regarding what type of reinforcement mesh, etc, in these posts?

[Les]

Re: Materials for Stucco Dome?

I added vermiculite/portland on top of the blanket. After that I tried to shape the dome w/mortar - then I applied the Dryvit - 2 coats. It's in my thread, Les' build.

Good luck,

Les...

[WaWaZat]

Re: Materials for Stucco Dome?

Found your thread Les... great stuff!

I'm a little unclear... did you do the chicken wire over the vermiculite, then mortar over the wire? So the mortar is your shells base coat, then 2 layers of acrylic over that?? No reinforcement for the acrylic layers, correct? What kind of mortar did you use?

In my case, I will not be using any armature or support other than the insulating blanket. My plans are to lay 1/2" hardware cloth over the blanket as tight as possible (see pix). I will cut the edges of the blanket on an angle to give it a smooth shape 1st, then my intensions are to form the hardware cloth as tight as possible to the blanket. I'm hoping to be able to base & finish coat over that.

Does anyone see any flaws with this plan? Other than that, just need to get clear on exactly what materials to use to give the shell strength & keep it water tight.

[Les]

Re: Materials for Stucco Dome?

I roughly formed the dome using rebar, then put the chicken wire around that. You kinda have to slop the vermiculite through the wire. At that point I just used type S mortar. I'm not familiar with hardware cloth so I can't help you there.

Les...

[WaWaZat]

Re: Materials for Stucco Dome?

I won't be using vermiculite. So I'm wondering if I should use something as a backing for the stucco or if half inch hardware cloth with a half inch layer of stucco right on the blanket will be fine.

Also, I've found this stuff by Quikrete called Qwikwall Surface Bonding Cement that supposedly I can pick up at my local Home Depot. 2 half inch layers of this mixed with their acrylic fortifier is supposed to be strong & water tight. Does anyone have experience with this stuff?

[ThisOldGarageNJ]

Re: Materials for Stucco Dome?

Hey wawazat,,
I used the Quikrete SBC,, I've said it Once I will say it a thousand times,,, LOVE THIS STUFF.... covered my block foundation and dome with it. Added the Acrylic fortifier for watrproofing and terra cotta color.. I have a 42 inch dome and used 2 bags just for the dome and that gave me 1/2-3/4 inch coverage...
For a smooth finish you can just trowel it on
For a slightly rougher finish you can trowel it on and wipe it with a grout sponge
One Note, You can mix by hand, but a mixer is recommended....
I also used half inch harware cloth for my vermicrete it worked fine,,,

Is there a reason your not using the vermicrete,,, Insulation is key to an oven..

Cheers
Mark

[WaWaZat]

Re: Materials for Stucco Dome?

Hey wawazat,,
I used the Quikrete SBC,, I've said it Once I will say it a thousand times,,, LOVE THIS STUFF.... covered my block foundation and dome with it. Added the Acrylic fortifier for watrproofing and terra cotta color.. I have a 42 inch dome and used 2 bags just for the dome and that gave me 1/2-3/4 inch coverage...
For a smooth finish you can just trowel it on
For a slightly rougher finish you can trowel it on and wipe it with a grout sponge
One Note, You can mix by hand, but a mixer is recommended....
I also used half inch harware cloth for my vermicrete it worked fine,,,

Is there a reason your not using the vermicrete,,, Insulation is key to an oven..

Cheers
Mark

Yes, this oven will have to come down in a year or 2 when I move. At that point I can see myself using more insulation... probably another layer or thicker blanket. Are people using vermiculite because it costs less? The blanket is just so easy to work with, why not use all blanket? Besides, I've noticed that the 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.

Anyway, you did one 1/2-3/4" layer? Did the 2 bags cover the dome and walls? I just have the dome, so maybe 2 bags even if I do 2 layers??

How much did this stuff penetrate the 1/2" hardware cloth? So much so that I might need some kind of backing over the blanket to fill any gaps... or, if I angle the seams of the blanket - smoothing out the gaps, do you think I can get the hardware cloth close enough and apply it right over the blanket? Does the Quikrete fall right through or is it sticky enough to adhere to the back of the hardware cloth when pushed through? If it falls through, maybe I can use aluminum foil to save the blanket so I can reuse it when I tear down & rebuild.

I have the rough look envisioned... is the the grout sponge used dry or wet?

Do you have a pic so I can see the terra cotta color and how you did your stucco finish?!

[WaWaZat]

Re: Materials for Stucco Dome?

Duh... right in your avatar!

Ok, I've seen your pix. So is the vermicrete you mentioned sort of a base coat concrete? I didn't realize this was a concrete substance... isn't regular vermiculite just poured in like a gravel/sand? Is that the brown layer? Did you use mesh for the vermicrete right over the blanket? Did you use another layer of mesh for the stucco? Did you finish your stucco with the grout sponge? Did you paint on your terra cotta finish?

[ThisOldGarageNJ]

Re: Materials for Stucco Dome?

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]

Re: Materials for Stucco Dome?

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]

Re: Materials for Stucco Dome?

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]

Re: Materials for Stucco Dome?

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]

Re: Materials for Stucco Dome?

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.