Repairing outside render slight gap

[fingersuk]

Always wanted a wood pizza oven so bit the bullet and ordered an etna oven. After nearly 5-6 week from order it finally arrived but stand was damaged so had to wait for new one.  Got it all moved with help of some friends.

Done about 6 easy burns in it and two pizza burns and quite quickly noticed so hairline cracks around chimney and roof, been filling these in with supplied mortar but seem to keep reappearing - any ideas how to perm fix this? Mortar does seem to breakoff on most of it on the next burn.

More concerning is the gap below. Not sure what todo with this....



Long term was thinking about k-rend but not sure how close you can get to chimney etc as it might add more wheatherproofing...

[ducky]

Hi. I've had a similar problem with my oven from etna. Although now I have a large chunk missing from the dome render. I'll post pictures tomorrow. I'm planning on adding extra insulation and then adding krend after. Have you spoken to etna about it.

[cobblerdave]

G'day
Metal of the chimney expands at a faster and greater rate than the render. Wrap a piece of cardboard around the metal chimney and render up to that. Remove the cardboard and seal the gap with automotive muffer sealer to give a higher heat flexible seal.
Regards dave

[fingersuk]

Thx will give it a go at some stage. Interested in pictures to compare notes. Have done but heard nothing if its anything like the slow delivery then damage goods he might reply in a few months.

I'm having other issues with cracked base now too not having much luck and fired it as he said

[downunderdave]

Use the method described by cobblerdave. The highest rated high temp silicon is Permatex Ultra Copper (371 C)

[ducky]

Here are the pictures of the cracks in my etna oven

[oblertone]

Your cracks look pretty serious for a preformed dome and I'd certainly be going back to the vendor for satisfaction; however, they are probably repairable, and nothing that a cob-builder wouldn't expect. Personally, I'd get a settlement from the vendor and then repair and cover with insulation & render before waiting for a replacement which might go the same way.

[downunderdave]

Looking at your pics it looks like you have a layer of vermicrete and chicken wire under your render layer. It looks very much to me like expanding steam in the vermicrete layer has caused expanding and cracking the outer render.
Did the manufacturer give you any instructions on the build? Or did you buy the oven fully finished?
Do you have a layer of ceramic fibre blanket next to the oven or just vermicrete?
If you have a vermicrete layer, how thick is it and did you dry it by firing the oven before applying the render coat?

[ducky]

The oven is cast from one piece. The interior refractory cement seems fine which is good news. I'm fairly sure the damage has been caused over the winter when water/frost has got in and caused the top coat to "blow". The oven came finished so I don't know what the insulation is, it not vermicrete as far as I can tell. Once the weather improves I'll add 4" of vermicrete and then top with k-rend. I got the oven ridiculously cheap just before last Christmas (£250 delivered, they must have been trying to get some cash flow in before christmas is all i can think) so I'm not going to bother going to the vendor as I was planning on adding more insulation anyway. They are £669 on their website now so I'd be pis**d off if I'd payed that but for what I payed, I'm still happy with it.
The only thing niggling at me is should I use ceramic blanket as opposed to vermicrete to insulate it?

[oblertone]

May 21, 2016 6:34:08 GMT ducky said:

Personally, I'd go for blanket, chicken wire and render as the easiest option for a good result; vermicrete isn't referred to as 'the Devils porridge' for nothing !