Igoo Dome Covering

[SandySpringsPizza]

I have completed an igloo shaped firebrick dome. The home-brew high heat mortar listed in the forum worked like a champ. I have cured the oven. I have wrapped the dome in 2" of ceramic blanket and I have covered the blanket with 1" of Econolite castible insulator. Since I can't immediately build a structure over the dome, I would like to add a layer of some kind of "stucco" or mortar to give the dome protection from the weather(though I will keep it covered with a tarp).

What do you suggest for an outer layer.

[gastagg]

The base layers of stucco are essentially a portland cement/mortar mix. Does your "castible insulator" have a smooth finish? If so, you'll have to use some type of metal lath to provide some structure for your stucco/cement/mortar mix. Does the castible insulator have no weather protection? Your tarp may do the trick until you build your enclosure. I just got done with the insulation/lath/stucco application over the last couple of weeks. Not sure I'd go through the trouble if it was only temporary.

However, if you want to go through the hassle of applying lath and stucco, there are 1-step applications that utilize some strengthening element (e.g., fiberglass) into the mix and would make it easier than the three layers that is common.

Have any pics?

[SandySpringsPizza]

Thanks for the reply.
The castible insulator has a very rough surface. It would seem ideal for "holding" any kind of stucco.
I talked to a stucco dealer and even with the insulation, he felt an acrylic stucco wouldn't stand up to the heat. Now I"m trying to figure out another cement based covering like 5-1-1, Sand-LIme-PC.

Thoughts?

[gastagg]

I used a portland cement stucco base with fiberglass reinforcement. But you shouldn't have any heat issues with 3" of insulation. I would look for a single-step stucco solution to put right onto your "very rough surface." Quikrete makes one. I used BASF's product I purchased from a pro concrete supply store. It's fairly easy to apply if you're just doing one step and not installing metal lath.

[david s]

If the surface of your insulating castable layer is a little rough I would not bother wrapping lathe around it, but just render straight on to the substrate as is. Most proprietary cement renders are partially waterproof, but you can paint over it with exterior acrylic paint for extra waterproofing. I mixx in fibreglass fibres with the render for extra strength, but be careful you must use AR (alkaline resistant) , unless you choose an acrylic render. The outside will never get hot enough to worry any coating. The outside will get hotter just sitting in the sun than it would from heat coming from the inner dome, provided it is insulated adequately. if you want to make up your own brew (cheapest) and has a degree of elasticity and crack self-healing properties, 4:1:1 sand,Portland cement,lime is pretty good.

[gastagg]

What did you end up doing Mark?

[SandySpringsPizza]

I ended up using a Quikcrete one step stucco mix that is reinforced with fiberglass. Worked great. I've had the oven up over 800 degrees and the exterior stucco feels only like it's been warmed by the sun.