How to Build a Cob Oven - Part One
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- Опубліковано 27 лип 2011
- Part One shows how to prepare the base and dome mold for building a cob oven. This oven is 36" interior diameter, so the height of the interior is 75% of that, or 27" tall. The thermal mass layer is 4" thick, plus a 6" thick insulating layer over that, so the whole oven is 10" bigger than the fire cavity all the way around. The base is made with stones gathered from the site and held together with a clay + sand (cob) mortar. Also note, the primary reason to use firebrick is that they do not crack under the heat of a fire. For more information on cob ovens, I recommend Kiko Denzer's book "Build Your Own Earth Oven"...it's a complete "how to" including how-to sketches, list of tools, inspiring photos, and much more.
We followed the three parts of your instruction video and produced an amazing cob oven, "Hestia," that fires up to temp in under three hours and can cook pizzas (600 F)for a couple of hours, followed by a couple of batches of sourdough (475 F), an overnight pot of baked beans and then some slow-dried granola with the residual heat in the morning (325 F)! We let our thermal layer dry completely before adding the insulating layer due to scheduling restrictions with no problems. We were able to source all of the components for the oven and shelter locally with many of them recycled right off the farm here. A wonderful companion for the cob oven is Richard Miscovitch's book "From the Wood-Fired Oven."
that's awesome! :)
Sheila Selby .
I built a cob oven a few years ago loosely following your videos along with videos from a couple others... usernames...
"jas. Townsend and son." & "work with nature" these in my opinion( along with yours) seemed to be the best at the time (I'm pretty sure I watched all cob oven and brick oven videos on UA-cam at least twice over that winter). My oven is holding up very well. I plan on making a video to show it off soon (wanted to see how it would hold up before giving my input to try save others from wasting countless hours of their life watching other videos). Thanks for the video.😀
Wow, Hello my friend.. All the best to your channel and hope you have a wonderful day
I CAN'T WAIT TO BUILD MINE! These videos get me all excited to try this.
These ovens make even the most plebeian of cheese pizzas taste like a gourmet tour de force!
Hell, anything baked in it is just magnificent IMHO...
Keep up the good work 🙏❤️
my heros used to be peter collins but that was back in 73 now its you siggy
thank you for your videos on How to Build a Cob Oven this will be a great outside project for the children at school
What a great reference for anyone wanting to build an earth oven. Thank you for all the details and easy to follow tips. I am looking forward to building my own and loved your videos.
So helpful. Thanks!
nice and clear - thank you
Excellent work guys!
Great video ready for part two:)
Definitely building one of these. I'm anxious to try building with cob and straw bales.
Your video series is the best out there on oven building! thanks for posting them.
My base is not going to give me enough room for 36" after all the layers are added but I would like to go bigger than 27". Do you see a problem with me laying down the bricks for a 36" but only building out to say 32"? That would give me the extra room for the insulation. Also, how much insulation do I need under the fire bricks? Some will be laying in part over the base stones ring.
Wow nice idea
Very nice oven, and a really cute builder. :)
1 as you mentioned...the bumpy road. You probably want to reinforce the surface with burlap or your high-straw-content insulating layer. Maybe make an internal support that you can inflate against the roof of the oven to support it during transport.
Awesome videos! I was just telling my wife. I've learned more from your few videos. Than I have in 3 weeks worth of researching. So thank you for your knowledge. The spring of 2015 is project time wink
That's awesome! glad to hear these were helpful to you. I also have a written-out step-by-step explanation here: buildnaturally.blogspot.com/2013/06/build-clay-cob-oven-in-your-yard.html
Thank you so much
thanks so much for the nice feedback! And I'm so glad if they were helpful to you. For your base, I'm not sure I totally understand your question about size, but the short answer is that you can make the oven any size you like. Just follow the proportions for the inside height and the door height based on your diameter (as noted in the video description). For insulation underneath, I actually skip this, as it does not seem to be the important variable to make the oven operate well.
A foot of charcoal instead of the sand and 5 inches of cob over the charcoal instead of the fire brick will hold the heat much better due to the insulating properties of the charcoal. On initial firing, after the cob has dried completely, keep stoking the fire until you have a good pile of red hot coals. It should be enough to cover the oven floor with at least 3 inches of coals. Spread the coals out and close the oven overnight. This will fire the cob into a hard surface.
Yes, I have definitely seen this done, though I have never done it myself. There are 2 considerations:
Here are quantities of each material from page 30 of the book "Build Your Own Earth Oven" by Kiko Denzer: 36" inside oven size (as shown in the video) = 11 5-gal buckets of sand, 17 5-gallon buckets of site clay soil (assumes 50% clay, 50% sand), 36 fire bricks. I have never used purchased bag clay to build an oven, so I'm not really sure the quantity for that. If I had to guess, I'd say about 4-5 50-lb bags of clay and double or triple the sand.
Yes, absolutely, you can take days if you like to build the oven. I would definitely recommend keeping the clay damp as you build, and a wet cloth of some kind would do that nicely. You can use a cement mixer to mix cob, though it will tend to be pretty wet, which will actually limit how much you can build in one day, since it will start to slump. For the door...it is about 2/3 the height of your oven interior (which is 3/4 of the oven diameter. Hope this helps! Good luck.
I love this video. It is clear and concise. I would like to know ( as I have Kiko Denzers book too) why some have a small tunnel from the domed oven with a stove pipe and some like this one, does not. What is the difference? Thanks again. Lovely!
I use firebrick because they can handle the high heat of the fire without cracking. Added bonus is that the corners tend to be really sharp, resulting in a very smooth floor. If you are concerned about the inert aluminum oxide component in the bricks, you can use whatever else you prefer for the floor. Just know if you use regular bricks, they may crack. If they crack, you can fill the cracks with ash from your fire.
Greetings Sigi,
I'm not sure my previous message made it to your site, but I love your work - thanks so much for sharing. I have ordered your book and am about to embark on making my own oven as per your instruction: A quick question: I do not see any chimney in your ovens, whereas most other models i see on youtube all have chimneys. What happens to the smoke in your model? Thanks again.
Edwin
Your version works well too. There is less aluminum in the firebricks than you breathe or eat in normal foods, and it's not clear that the aluminum would be absorbed into any pizza or bread cooked directly on the bricks (definitely not into a pot of food). But if you want to avoid, by all means you can do a clay floor. Not sure what you did to ensure that you don't get sand in any food cooked directly on the clay...feel free to share that too.
My oven is almost ready. Thanks for all the help. I have one more question, though. My bricks aren't as neat as yours and there is space in between them. What do you recomend to fill the gaps so that the pizza dough don't get caught. Could it be adobe (won't it stick to the food?)
Good points about the oven floor. I wouldn't want to risk a sandy pizza!
Speaking of cleaning, I'd appreciate seeing how that's done. I imagine it's a real pain struggling in the small door to try to scrape out the ash, etc. in the dark dome interior. I hope I'm wrong.
Finally, is there any maintenance to a stove like this?
Thanks for your help!
Thanks so interesting. But how is that rock base constructed? I'd love to learn how that was created.
Hola:
Antes de entrar en materia, dejar claro que mi inglés no es muy bueno, por lo que no he comprendido la mayoría de los comentarios de los 3 vídeos. Teniendo en cuenta este punto, es posible que en los comentarios hayáis dicho algo relacionado con mis comentarios.
1m15s a 1m40s:
Si no compactáis la base del horno -teniendo en cuenta de que no habéis utilizado mortero- el centro de la base del horno se hundirá con el tiempo. Dicho esto, también he tenido en cuenta de que habéis utilizado ladrillos refractarios (o eso parece), pero aún así, la base se hundirá.
La consecuencia directa es que tendréis que desmontar los ladrillos para añadir más arena -o tierra- para rellenar lo que se haya hundido la base de ladrillos.
En cualquier caso, es de agradecer la iniciativa de publicar los vídeos para todos aprendamos que tenemos un mundo de posibilidades a nuestra disposición.
Saludos.
cok guzel firn yapiyorsunuz iyide biz de sizin gibi genis arazi yok camurda bulamiyoruz taslarda cok pahali amma guzel firin yaptiniz tebrik ederim kac gun de bitirdiniz onu merak ediyorum ?
Why does the fire brick have to be the bottom surface? Couldn't it be covered with a layer of cob to make it perfectly smooth?
There is a defined height for the door opening (depending on the size of your oven), but the width can be whatever you want. So you can make the door opening large enough to clean out easily. Part three talks about firing and cleaning the floor, but basically you use a damp COTTON mop or rag. Do not use any synthetic materials, as they will melt onto your floor. Maintenance depends on the finish you put on the oven (again discussed in part 3, which should be online soon).
The fire brick doesn't crack under the heat of the fire and provides a very cleanable surface to bake your pizza on. You could experiment with a cob floor, though you may find some cracking in the surface and you may need to use a pizza stone to avoid sand in your pizza.
thank you, respect! 8-)
I was wondering where can I get fire bricks?
@sigikoko ah nice, thank you very much
Another video I saw used a template made out of wood for the dome to create a perfect sphere
Wonderful. thank U for sharing it!
can u tell me more about proportion between base diameter and cob high?
About the door?
Peppe Bruno the inside diameter of the base determines all other dimensions. The inside height will be 3/4 of the diameter. And the door will be 2/3 of the inside height, which also works out to be 1/2 of the diameter. It's also written in the text of the video, in case that is helpful.
buildnaturally Thanks.
I built my cob oven some weeks ago(in truth i built only the cooking chamber and i'm waitin' for better weather to build the isolation chamber). the diameter is about 70 cm, the inside height 50 cm and the door something about 28 cm. So, as you advise, I can take more space for the door.
Thanks for sharing your knowledge!
Part Three is officially up! And if you read the notes I wrote at the bottom of the video, I wrote out the dimensions to calculate the diameter, the inside height, and then the height of the door.
"breathable"- Meaning poop smell good, yadidameen?
J/k
Thank you for the great, well presented information. Bravo
I want to rebuild one of my ovens because it is a little too high inside and it has a huge crack inside too. I intent to make a new mix for the inner layer, but can I re-use the old material for the insulation and the cover layer?
sure, as long as you didn't add any other binder, you can always re-saturate the clay
Can you tell me how many brick and how many bags of clay i have to buy to built an oven like yours.
Diane Venne
@awakaraga you're welcome...sorry again for the confusion!
I would try a masonry supply place or ask a local mason where to get them in your area.
Hi, thx for the great vid. I'm from the Netherlands, with less clay in my backyard. so i want to buy some claypowder on the internet to mix it with the sand. My question is what sort of clay powder it is? Is it "chamotte" clay powder(same as the material the firebricks are made of)?Note that chamotte powder is clay that is already being baked at a high temperature.
any clay is fine. If you are purchasing as a powder, I would get the least expensive option. And then don't forget to add sand to your mix, or you will get lots of cracking with just pure clay.
What are the big rocks around the base and where did you get them?
they are just rocks that were around the area where we built the oven, and they only serve to lift the floor of the oven to a more comfortable height for cooking.
Hi, our soil has just a little clay in it. I purchased fire clay to augment, if I just used fire clay would I still use a 25% to 75% clay to sand mix? Thank you.
you have to do tests to get the exact proportions....every type of clay is different (it's just that most clays work with about 25% clay, 75% sand)
Thanks, one more question please. Does one have to put the cob layer on the same day the thermal layer. I won't have as much help as you did and I'm a little concerned.
nope you can do them whenever your particular timing permits. I usually do the insulation the day after the cob mass layer, because I'm usually teaching a workshop. But you can take as much time as you like between.
Finally finished my oven, hoping to have pizza over the weekend. Thank you for your help, Randy.
have you ever made a cob oven from 100% found and local materials? Would using an iron smelting furnace as a kiln be able to create bricks for the bottom?
yes, I have. Don't know about the iron smelting furnace question...that's beyond my personal experience.
buildnaturally ah. so cobb is fine to use as the bottom? perhaps a baking stone or some extra corn meal would be used.
Hi could I use a Yorkshire stone flag floor over a layer of wine bottles instead of fire brick for the floor
you can, but there is a caveat...stone can be prone to cracking under the heat of the fire. also, the stone typically gets hotter than the fire brick, so you may have to "soak" the oven longer, or have a tendency to burn the bottom of baked items (bread, pizza, etc.). But yes, in theory.
I would actually use the ash from your first fire and let that pack into the cracks. If you use cob, you risk sand or grit in the bottom of your pizza or bread. The ash won't be bothersome. Hope that helps! Let me know how your first pizza goes...
@awakaraga I posted a new "part two" video, sorry for the confusion. Try going to my channel page and the new & improved Part Two video is featured there.
its says part 2 is private :S
What percentage of clay and sand? Thanks
+Chayne Michaels It depends on your particular clay, but a good starting point is between 25% and 30% clay
how did u make the base
we made a ring of stone, held together with cob mortar, sitting on top of a gravel spread-footer to keep it stable on the ground
buildnaturally it is the base that I need help with. Did you happen to video it while you were making it? How did you decide on the size? How long did it take? Can you do a rectangle for a Canadian shaped oven? Love your videos!
My Cob Oven is over 99% clay and sand, i didnt use any brick. Its an Rockt Stove Cob Oven made out of 2.2 tonns clay/sand/straw/wood. I can heat it up to over 600°C and it still works fine after over 3 month. Total cost 0 € and 32 work hours.
My problem is Aluminum Its a neurotoxin!
I will upload some Fotos on Facebook later
That brick pattern made no sense to me, so I looked up patterns. Wouldn't a "herringbone" pattern have been stronger. It seems like common sense to me, but I know nothing about brick laying and cob.
the pattern doesn't really matter as long as you can install tight, so there are no gaps between the bricks. This is just the method that is easiest to me for teaching purposes.
Nice, should tamp sand prior to placing bricks
yes, for sure
She must have strong hands, those bricks weigh about 7 1/4 Lbs. each
2 is the weight...and here you probably would want to build a smaller oven (24" diameter max.), or else the weight is astronomical. cob weight approximately 17 lbs per 12" x 12" x 1" volume (adds up fast!) Are you on facebook? I can direct you to a forum where folks have done this & they could share their solutions.
ok, so check out one of these fb groups:
facebook.com/groups/naturalhomes/
facebook.com/groups/naturalbuilding/
if you want to reduce/eliminate cracks, let the cob dry slowly & completely before firing. You can fire it up sooner, but know that you will likely have cracks. I also like to fire it up at least once prior to plastering. Hope this helps!
Why fire bricks ? Why not just use a cob base ??
اني عربي وعشق الريف الجميل ول الخضراء الروعة بنت ريفية أصيلة روووعة 👰 👰 👰 👰 👰 👰
Great to see, that woodprix has new instructions to save my money and energy to build it.
Why Firebricks? They contain Aluminium!
Because they dont crack with the extreme temperatures in the oven
Thank you so much