Chimney connection

[Patrick.S]

Many years ago I built a cob oven for my parents. It came out great and I imagine it is still in use by whoever owns the house now. The oven at that time was a chimneyless dome, straight up Dezner style. Now I want to build an oven for myself and I would like to make some improvements to the first design. The thing I've had a really hard time finding is how people are connecting a metal chimney to the cob of the oven. Some of them just seem like they just surround the chimney pipe with cob. My concern with this is expansion of the metal that could cause the cob to crack, perhaps less of a problem with double wall pipes. I don't often see anchor plates integrated into these ovens. Am I missing something?

Another quick question. I read that people use stainless steel chimneys because flue gasses are corrosive and the chimney won't last three years. Now I'm sure that's true, but I've seen old cabins with rusty old stove pipe that's been running a woodstove for decades. Is there something about a WFO that corrodes a pipe faster? Is it the high heat? Some of those woodstoves can pump it out too. Am I missing something again?

Thanks for the help!

[SableSprings]

Welcome Patrick! As you've probably noticed, most of the builds here are brick or cast. Although there are some cob ovens documented, you might find the best solutions to setting your chimney in the threads dealing with casting. I've put in two links below for you for threads that have some good discussion and pictures about connecting the chimney. Note that the first thread uses a clay flue pipe instead of metal. Both threads also talk about dealing with heat expansion at these "joints".

https://community.fornobravo.com/for...shelbyville-ky

https://community.fornobravo.com/for...ver-sand/page4

Old cabins using rusty woodstove pipe are generally living on borrowed time (IMHO) I am pretty sure that if these stoves were installed with the current understanding of fire safety & building codes they would not be using the same pipe & flue systems

[Patrick.S]

Thanks for the response! Those threads were great. I'm actually on the fence considering cast for this oven. I guess the chimney issue is similar in both mediums

[purplehaze]

Patrick my SS chimney transition sits flat on top of the oven transition, any gaps were filled with high temp caulking. I would suggest that when you cast your oven transition you make it as shallow as possible to make it easier to move food around in the oven.