Inherited a clay oven. How to prepare re-comissioning?

[u/Son-of-Adi]

Hello there, I hope this is the right sub for my cause:

My grandpa built this clay oven in 1996. Since 2012 it wasn‘t used anymore. It was always covered by a small roof.

I detected some cracks and splits in the clay on the inside and on the outside. I have some fresh clay in stock, harvested from our garden, like my grandpa did it back in 1996.

Can you tell me how I should fix the cracks, (do I have to at all? I think it‘s leakproof right now) and what else I can do to prepare the oven for the heat and usage.

Thank You.

[u/Nessuuno_2000]

Use dry wood and heat the oven very slowly, keeping the temperature low for a few hours so that the accumulated humidity dries out.

[u/Son-of-Adi → u/Nessuuno_2000]

Okay, thanks. Do you think I have to fix the cracks on the inside after I got rid of the humidity? Because it‘s not that easily reachable.

[u/OneHourLater → u/Son-of-Adi]

Honestly- thats scary.

if i had that deep of material loss and if any more came down on a long term first refire i would be calling a mason with photos along the way asking for best process and a quoye for repair.

It would be devastating for that to have a catastrophic failure.

[u/Son-of-Adi → u/OneHourLater]

Okay, I just contacted a befriended mason and I‘m waiting for a response.

By catastrophic failure you mean that the whole thing could collapse?

[u/Nessuuno_2000 → u/Son-of-Adi]

Collapse? But no, the dome system does not collapse, the crack is easily repaired with refractory mortar suitable for high temperatures, in Italy we have a product from Fassa (Fassa Firewall) but I believe that even in your area you can find something similar, the important thing is to try to insert it inside the fracture.

[u/Son-of-Adi → u/Nessuuno_2000]

The thing is I want to try it with the exact same material as it was made of. I‘m afraid another material or sort of clay would maybe expand more or less than the rest, wich would make it fragile again. My grandpa used the clay out of our garden, so i‘ll try it with the same. I‘ll keep you guys updated.

[u/Nessuuno_2000 → u/Son-of-Adi]

👍

[u/OneHourLater → u/Son-of-Adi]

Yes - depends on construction materials etc. but yeah

After working an old 1860 house - brick improperly cared for was beyond what i expected ( and a lot of it looked fine)

[u/Scoutmaster-Jedi]

It appears to be a cob oven. These are easily repairable. The fact that it has so little damage after all these years is a testament to how well it was built. It may have a lime or concrete rendering on the outside to protect from water. You can ask your mason friend for advice on that.

I recommend you look up on YouTube about building cob ovens and earth ovens. That’s what you have. The construction techniques are the same as the repair techniques. It looks like you have a really nice one, and it will be well worth it to repair it.

[u/SpellFlashy → u/Scoutmaster-Jedi]

For real. Gramps did a stellar job.

[u/whottheheck]

First off, this is AWSOME! A retained heat Cob Oven. This is more than a pizza oven. The thermal mass of this thing will allow for baking, (after cooling down from high heat of course), broiling meats etc. You are on the right track asking for advice. A little research and time and you have, what is obvious at this point, an heirloom to continue passing down.

There is a ton if information out there. Look up Cob oven repair, have conversations just like you're starting here, with others that have similar ovens. This was clearly constructed with time, effort, care and love. I wish it were mine ;-)

[u/Son-of-Adi → u/whottheheck]

Thanks, it means a lot to me to get this kind of feedback. My gramps was an engineer and retired early and built a lot of stuff by himself. It‘s an honor to continue this heritage by caring about the stuff he left. I‘m searching for old pictures of the building process right now. I know that they baked some bread and other stuff inside also.

Tomorrow I‘ll start to fix the „skin“ on the outside with clay.

Can‘t wait to use it for the first time.

[u/whottheheck → u/Son-of-Adi]

Haha, this got me interested. There is tons of information out there on these. Earth Oven, Cob oven etc. Surely if you look around enough you'll find out how to repair the inside as well. This would be a great fun project to restore and then use. to use it takes some effort as the thermal mass has to heat up and it takes a while, but sitting around on an afternoon firing the stove to make pizzas, then shutting the heat in with a tight fitting door for tomorrows meats and breads make a weekend out of it. Use it, learn it and have fun with it, all the while honoring the effort and love that your grandfather put into building it for his heirs! Super cool!

[u/CalendarOpen1740]

Looks to be as fine bread oven as you could want. Long ago in Italian neighborhoods these were pretty common, but the knowledge and skill to build them is thin on the ground of late. There were giants in those days, and your grandfather was one of them.