exterior dome finish keeps cracking

[fabby]

Hey guys, when I finished my oven dome, I used a stucco mix that held up well for the first year and a half, but the second winter I had some cracks develop. That spring I recovered with some 5000 quickcrete after using the oven a few times to make sure it was dried out well.

This winter I decided to cover with a tarp, just to be safe. The dome cracked and most of the quickcrete was a disaster, so I just peeled off.

Now I am thinking what to do, recover or build a enclosure? I like the dome look but would like something more long lasting.

Thanks for your thoughts.
fabby

[jeeppiper]

Re: exterior dome finish keeps cracking

Plain old concrete and stucco are porous and can act like a sponge. With the crazy winter we had, any trapped moisture in the concrete can freeze and cause cracking. You would need to seal the stucco.

It is always a safe bet to put a roof over it. That way you will know it will always remain dry.

[david s]

Re: exterior dome finish keeps cracking

You could try an acrylic elastomeric product that has a lot of elasticity that will cope with the expansion as well as waterproofing it.

[fabby]

Re: exterior dome finish keeps cracking

Attached a photo of what I planned to do as I will probably just enclose the dome, and leave the chimney exposed? Or should I enclose the whole thing and try to figure some high heat flashing for the chimney flue?

[fabby]

Re: exterior dome finish keeps cracking

david s, is there a product available that you would recommend?

[cobblerdave]

Re: exterior dome finish keeps cracking

G'day
I've covered my dome with house brick split in 1/2 lengthways. House r
Bricks are water resistant and the structure is thicker and tougher now( kid proof). Just as importantly it lets me keep the igloo shape I like and no roof which is what I wanted.



Regards dave

[Les]

Re: exterior dome finish keeps cracking

david s, is there a product available that you would recommend?

Dryvit - the product is awesome. I need to add a little to the base where the ice has chipped it in a few places but it's been through 6 winters...

[fabby]

Re: exterior dome finish keeps cracking

Cobblerdave, what type of mortar did you use for the exterior dome bricks?

[cobblerdave]

Re: exterior dome finish keeps cracking

Gday
Just standard brick mortar with the addition of powdered clay to give it workability like the homebrew
Regards Dave

[cobblerdave]

Re: exterior dome finish keeps cracking

G'day
Before I forget there are brick sealers out there you could use as well. They are as thin as water and soak into the surface. I never found the need to use them but they could be helpful in your situation for a complete seal before the winter freeze.
Regards Dave

[david s]

Re: exterior dome finish keeps cracking

david s, is there a product available that you would recommend?

I use stuff called flexible pointing. It was developed for sealing ridge cap tiles on for th roof on houses. It is highly elastic to cope with the constant expansion and contraction and is also very UV resistant. Being acrylic I water it down so it can be applied by brush. Around 3 coats gives a 2-3 mm thickness. There are lots of different manufacturers for this product.

[softy]

Re: exterior dome finish keeps cracking

a high strength ( extra extra cement ) concrete mix with 10mm aggregate will work well. do 2 layers of 40 to 50mm thick, easy to shape if you mix it stiffer. there is a water proofing liquid made by silastic I think, that you mix with straight cement, mix up a paste and paint it on, does wonders, my oven is buried half in the dirt, we are coping a belting in Sydney as I type, no problems as yet with my oven, the cat sleeps on top of the dome even while the oven is fired up.

[fabby]

Re: exterior dome finish keeps cracking

So I removed most of the old layers of cracked stucco, almost down to the wire support. The fiber blanket seems to be kinda wet, I have been tarping to keep rain off and uncovering but it still seems damp. I alsostarted a small fire in the oven as well.

It has been cold and wet the last couple of days, and not high temps. Should I continue to wait for the blanket to try out, or go ahead and stucco now?

I was hoping to make pizza next weekend but at this point I don't know whether to not do anything, and go ahead with the pizza party with an ugly oven, or just stucco and try to cook anyway,


or switch to a bbq party.........

[david s]

Re: exterior dome finish keeps cracking

So I removed most of the old layers of cracked stucco, almost down to the wire support. The fiber blanket seems to be kinda wet, I have been tarping to keep rain off and uncovering but it still seems damp. I alsostarted a small fire in the oven as well.

It has been cold and wet the last couple of days, and not high temps. Should I continue to wait for the blanket to try out, or go ahead and stucco now?

I was hoping to make pizza next weekend but at this point I don't know whether to not do anything, and go ahead with the pizza party with an ugly oven, or just stucco and try to cook anyway,


or switch to a bbq party.........

If you stucco now and then fire the oven you will risk cracking the outer shell again when water in the blanket turns to steam.
Better to fire the oven, have your party and when the oven is totally dry, do the stucco layer and cover it for a week to enhance strength. I wrap the whole oven in cling wrap for a week to keep this moisture in the outer layer. Unwrap the oven fire it up around ten times and then apply a waterproof coating.
Others may disagree with my method but it has worked for me (many times).

[Gulf]

Re: exterior dome finish keeps cracking

If you stucco now and then fire the oven you will risk cracking the outer shell again when water in the blanket turns to steam.
Better to fire the oven, have your party and when the oven is totally dry, do the stucco layer and cover it for a week to enhance strength. I wrap the whole oven in cling wrap for a week to keep this moisture in the outer layer. Unwrap the oven fire it up around ten times and then apply a waterproof coating.
Others may disagree with my method but it has worked for me (many times).

I'm not disagreeing with any of the above, but I still recommend a vent .