arch crack created stucco crack

[leckig]

I have 3 small cracks in the arch that open up only when the oven heats up. They did not bother me.

The arch is insulated, but I made a mistake - when applying the stucco I covered with it the whole arch up to the very edge of it. So yesterday, during a nice fire the cracks in the arch opened up and... they decided to open up the stucco as well.

I can easily fix the stucco, but I am looking for ideas how to prevent the cracks in the arch to propagate on the stucco. Obviously, I the stucco cannot touch the bricks, what can I use to fill the between the bricks and stucco?

[fxpose]

I had one area above the vent where the base coat stucco kept opening up only during roaring start ups but after shimming that crack while open I filled the crack with very fine stucco mix.
After several days I applied a couple of layers of SBC w/acrylic over that and I have not seen a crack there since after several firings.

[leckig]

This is an interesting fix George! The crack in my case is all together at least 4 feet long.

Is there a technique which allows to separate the stucco from the bricks, so if the cracks in bricks expands it will not crack the stucco? Maybe there is some kind of expanding or rather flexible compound I can use it to create a sealed gap between the edge of the arch and the stucco layer?

Greg

[david s]

Try a flexible acrylic render/stucco mix

[sjmeff]

Greg - I have a stucco dome and I left a thin space (~1/8", perhaps?) between the stucco and my Duratech chimney and between the stucco and my outer arch. I filled the space with clear, high-temp caulk. The stuff I got is supposedly resistant to weathering. After a year it's as good as new and so far my stucco has held up.

I have an extra can of the caulk that I'd be happy to send you. Send me a private message with your address if you're interested.

S

[sjmeff]

I also used SBC with acrylic mix for my stucco as David suggested in his comment.

[leckig]

high temp caulk - this sounds like what I need!

I appreciate your offer! Which product did you use, if I can buy it locally it may be cheaper and faster.

I dont think SBC with acrylic would be sufficient - I just cant imagine it would stretch to 1/8 inch.

[sjmeff]

This looks like what I got but I'd have to double check. The link indicates that it has an upper temperature range of 500F, which is way hotter than either my double-walled chimney or outer arch get (both do get hot to the touch, but I can put my hand on them for several seconds).

I ordered 3 cans and they sent me a few extra. So far I've used one, so I have several left over.

Regarding the SBC, I just meant that overall it's durable for the rest of your dome, but I don't think it will necessarily solve this issue.

S

[leckig]

Thanks! I will check Lowes today, if I cant find anything that may work, I will send you that PM.
greg

[david s]

On my ovens I leave a gap of 10mm between the outer arch and floor which is filled with vermicrete. This seems to be sufficient to eliminate cracks around the arch. I have also created a unique seal made of terra cotta that goes around the flue and also allows the oven to breathe. This also eliminates the cracking problem around the flue, which can be an easy access for water entry.Checkout my website to view what I'm talking about.

www.davespizzaovens.com.au