Cob Oven Build from Start to Finish
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- Опубліковано 25 тра 2017
- UPDATE: I painstakingly edited the automated UA-cam captions (mainly so I don't have to read any more complaints about the volume 😝 - see below). Enjoy!
This isn't a tutorial - it's mostly for friends who have asked for the story of how I made my cob oven. (I know it's long - if you want to breeze through, you could play it at 1.5x speed and it'd be totally legible. I talked pretty slowly throughout.) Here is a link to the Kiko Denzer book that I mention in the video: a.co/3VfoBk4
** Sorry for the low volume. In addition to being sick/tired at the time I recorded it, I didn't check the levels before posting it. It's totally legible - you just need to turn your volume up louder than you normally would. Or turn on the English subtitles, not the computer-generated ones **
I actually like the lower volume of the voice over. The world nowadays is far too loud & filled with extraneous noise. Listening to & watching your video was relaxing & informative. Thanks.
I have the volume full out and I can't hear a darn thing
Enjoy the pictures :) (also, I took a couple hours and updated the captions so they are accurate.)
Nice work, love the lime finish and the rain catch off the structure very Permaculture!
The cob oven was cranking tonight: live-fire roasted asparagus, beets, cauliflower, green beans, ash roasted onions and sweet potatoes, and roasted garlic. First time I've used it in months since we had a giant tree fall on our house and had to live elsewhere. I fired it for an hour, left the ashes in and a small live fire. I did start the fire up again half-way through all those pans because it was dropping under 500*F near the door. A deeper oven would be better for this since I'm using a long-ish tray. I really intended for this to be used for bread, but at the moment I'm not eating any grains, to see if it affects an autoimmune disease I have. Hopefully I'll be back to bread, at some point but roasting vegetables in a hickory or pecan fired oven tastes great!
Rob Duarte so awesome!
You my freind are truly enjoying life ..the simplest of things bring great joy
That was enjoyable. Thanks for posting your second thoughts as well. It really is all a matter of experience. There seems to be no obvious perfect way to build one ; )
That’s why we add straw in cobe, it makes it stronger and regulate the humidity for a slow drying and avoid cracks
Wow! thanks for this great video. A little long perhaps but very well explained, no weird music, quiet pleasant voice/tone and follow up comments. Great Job Thank you so much.
Many thanks for this! Great job.
Titluj na srpskom
This is such a helpful video!
Couple questions: what was the diameter of your oven floor (interior)? Also, how much of the red clay did you end up using? I think you said you bought a yard, was that enough or too much?
Thanks for sharing video.step by step explaining good....
Just started vid, thx for this btw. Into cob stuff right now. But too the point, you have an relaxing voice, like npr or this American life, quality. It relaxes me, ever consider radio or something to that effect?
Its seriously long including much trivia... I'm about to nod off - with a cup of coffee in my hand!
You have a nice calm voice, but man... The final version with the very big exterior insulation looks very nice. good shape!
Builder I'm glad you're enjoying my soothing voice. As I said, it's not meant to be a tutorial - it's more of an update to people who heard me go on about "the oven I'm building" over the course of the prior year. I do know how to be brief and to the point, but that wasn't my goal for this video. :) If you're looking for technical info, check out the books mentioned in the description and the comments.
This looks awesome! I like all the details. 😊👍
very nice video, thanks for sharing 👍👍
My ground is heavy silt sandy loam even at 2' depth. That won't work will it? I sun dried a brick out of it and there was very minimal shrinkage. I scratched a 4" line in it that shrank to 3.75". It seems pretty hard and has that ceramic sound when tapped, somewhat hard to break. PS a coffee stand is where I found lots of thick glass bottles. Wood stoves can be found for nearly free and are lined with firebrick. I'm still just gathering materials. Thanks for your video.
I think you really need clay. I ended up buying a clay-sand mixture from a quarry company really cheap. My feeling was that I was going to spend a lot of time and energy making the oven and I wanted to give it every chance to have a long useful life. I figured starting with the wrong material for the dome would be a big mistake.
You do know if you want it to dry but not crack as bad initially you don't build a full fire. You first just burn paper. Then each time you fire it add a little more wood. Start with twigs. It will help it dry but slowly so it doesn't crack.
Love your build. Fantastic job. Could you please share the recipe for the cob? Did you eventually mix your own cob for the plastering on the newspaper or did you just use the ready mix that you purchased?
I used the clay/sand mix that I purchased. I do think I should have added more sand to the mixture, though. I'd recommend using the ratios in Kiko Denzer's book - I was off because I didn't know how much sand was in the mix I already had, and I underestimated how much sand I would need to add to it.
@@RobDuarte Thank you for replying. Take care
Watch the video!
Thanks for the vid. Any idea how much sawdust you ended up needing for outer insulation layer?
Fabulous!
Thats why they add the straw to the cob not only does it make it stronger but it adds insulation
Great video. Question, the insulation you used is the cob (clay+sand+water) + sawdust and then your hearth floor or subfloor (what you filled your circular mold with) is only the cob mixture? I am trying to repurpose some cob + straw mixture and I'm not sure if I need to make just some cob (minus the straw) for my hearth floor. Or do you think I can use it for my insulation and fill my mold with?
No, the "hearth subfloor" is meant to store heat so it needs to be the cob mixture without the sawdust. That cob+sawdust/straw mixture is for insulation - so the heat that gets absorbed by the "hearth subfloor" will stay in that thermal mass and not escape through its bottom (and into the foundation etc).
@@RobDuarte Thank you. Also the clay/sand mix you purchased - was it fireclay/refractory cement?
@@rosie6486 no, it was just red clay from the ground. Quarry/sand/gravel supply-type places down here sell it for use as a foundation material for construction. Because everything in Florida seems to be built on dirt (on top of crumbling limestone) 😂
Do you think you could use this as a kiln for pottery? I see similarities with brick or mud ovens and outdoor kilns
No, this doesn't get to those temperatures. Wood fired kilns are normally built with refractory or fire bricks and need specific venting, creating drafts that increase the temperatures possible. I don't know much about building wood fired kilns but there is a lot of info out there.
cool info thanks. I am thinking of moving to Florida, Do you know of any Cob houses being built down your way? My hope is to build with both Cob and straw bales for my barns and other buildings. Any information would be greatly appreciated.
Sorry, I don't know of any cob or strawbale buildings. It's pretty wet here - most of that seems to happen in the southwest US. A neighbor of mine knows a lot about these types of building techniques, though, and was planning to build an adobe house on her lot in my neighborhood. She ran into money problems before she could get started though.
@@RobDuarte thanks for the response, been digging a bit more found this Q&A on green building website.
"there is no reason why you can't build with cob there. Cob has been built successfully in very wet places like British Columbia and Wales. If you get very frequent rain you may want to put up a big tarp over the site during construction, or build the roof first. As long as it is carefully designed and built (good high foundation, adequate roof overhangs, protective plaster if necessary) it should last a very long time. However, that doesn't necessarily mean that cob is the most suitable building material for that area. In a dry climate like the high desert, even when daytime temperatures are very hot it still gets cold at night and the heat absorbed by the cob during the day can be discharged. In a hot moist climate where nights are warm, high mass materials lose their passive cooling abilities. You may need to augment with mechanical cooling. And a lower mass building system (like straw bale or wattle-and-daub for example) might be more efficient."
I also talked to my realtor and he said buy land in AG zoning with no deed restrictions and farm buildings like sheds barns coops etc,. can be built with whatever materials you want all they care about is the roof isnt going to blow off. Others have built "Workshops/Sheds" and "converted" them into living space. There may yet be hope!
@@angelcastro3129 Yes, you can definitely build with cob here - I did it with the oven. I just had to have a tent over it 90% of the time. But once the structure is built and the tent/tarps are gone, you'd need to have a pretty solid plan for keeping the weeks-on-end of rain from damaging it. Obviously the roof isn't made of cob, but I think you'd have to really figure out the drainage and also definitely use some kind of protective surfacing like I did with the oven: lime plaster and lime wash. I could never have this oven without the roof over it.
@@RobDuarte Cool beans, I'm looking for properties with no deed restrictions and thought I should first try building a prototype using it as a barn to see how well it holds up with any luck I might convince the local building dept that it is a viable option.
Hi there! I dont recall seeing a chimney design in the Kiko book. Did I miss this? any help on adding that in? thanks!
He briefly mentions it in the book . I didn't plan on including one until I saw how it would help my specific oven. Not sure if I'd plan to have one from the start next time...
Did you grout the big
cement pieces together at all? Also, where can we get the clay material you used?
Nope, they're just stacked. The clay mix I used is something that they sell for foundations here in FL. You see it one construction sites before they pour concrete, etc. I wouldn't use it again without adding more sand to the mix.
Rob where in Florica are you located and where can I get the clay? I live near Leesburg.
I'm in Tallahassee. I got it from Crowder. The material is red clay that they use for building foundations. I hope that helps.
I’m getting really inspired in Illinois
wont the bottle explode once heated or crack later leaving behind a hollow points...???its it okay to used them as u did.?
xcel cd I don't believe so. They are pretty hearty bottles and there is some distance between the very high heat of the oven interior and the bottles. also, the reason they would want to crack is not from heat but from cooling too fast, and I would think they would be losing their heat quite slowly, like the rest of the oven. Finally, even if a bottle broke in there, I'm not sure what effect it would have... There would be a void since the surrounding material is all hardened at that point, and that void would be just as good insulation as if the bottle were intact. The bottles are providing some kind of support for the material above, but I really don't think they're breaking.
thanks for the instant reply.
btw if your aren't facing any problem with your oven in that matter then it should be ok..also, can we used aluminium foil, for further insulation.?
I wouldn't. The idea is to have the shell be made from materials that are "breathable". I think a layer of aluminum foil would defeat that goal. I also don't know if it would have much effect. I think Kiko Denzer mentions it in his book as something someone had asked about at one point and I think his answer was something along the lines of: go ahead and try, why not?
Rob Duarte i see, i wouldn't go for the foil since your answer make sense. Thank you again.
What is the clay/sand building mixture you bought called?
It was a mix that a local Florida company (Crowder) sells by the yard for making foundations for buildings.
Why do the limewash when you have a substantial rain cover over it?
Looks good? It's a natural finish that can just get applied whenever it starts to get blackened from smoke. Some people put mineral pigments in the limewash and add decoration that way. (I also wasn't confident that a leak in the roof wouldn't appear at some point and maybe go unnoticed while it damaged the dome. It never did leak, though.)
One addition might be to use a layer of aircrete over the top to help hold in the heat.
The outer shell needs to be something breathable - I know concrete is not a good idea, not sure about aircrete
Qual à função das garrafas quebradas na base do forno?
Insulation. To keep the heat from leaving the brick floor and going into the foundation (where it would be useless)
How's that roof holding up after a few years? Looks like the first hurricane will launch it into the next county.
It's been through plenty of storms and hasn't had any problems. Looks the same as when I built it.
thx
Rob, what's the diameter measurement in inches of the sand base of your oven? How high is the oven?
Not sure what you mean by the sand base. Are you looking for the interior dimensions of my oven?
yes
About 23" diameter / 15" at it's highest point (which is not the center, as I described in the video)
Cob is traditionally clay, water, straw and sometimes lime (or sand) so the cracks are appearing because there wasn't organic material and didn't get the strengthening it needed
Wouldn't the organic material get burned out?
My father wants to know why put bottles of wine in the bottom of the oven? thank you
The bottles are empty. They become pockets of air underneath the floor of the oven. Air is a good insulator. This insulation keeps the heat that's in the fire bricks (and the mass of clay underneath it) from escaping into the stone foundation.
are the foundation stones mortared together?
No, the big stones at the bottom are just dry stacked. The layers of regular red bricks are mortared together.
Forgive me, I'm a numpty when it comes to building but what's the advantage of not mortaring the foundation stones, given you had mortar for the bricks?
Great job btw, I really admire your persistence and how you kept adapting the insulation until it worked.
thedr00 they're such heavy stones that I didn't see the need to stick them together. I'd also end up using a ton of mortar given the big gaps between them. I was trying to keep things only as complicated as they needed to when possible and mortar just seemed like an extra step. On the other hand, you don't often see bricks without mortar and it seemed to make more sense to mortar them than not.
Got it. that makes sense. Thanks for your answers and enjoy your oven!
Can we use broken glass pieces instead of bottles
Look at the replies to Adem below
@@RobDuarte Thank you so much
I guess you drank all the contents before you cut the bottles up Rob ? 😂😂🤘🤘🤘
Not a one - they all came from the alley behind a local "paint n sip" business :)
Do the bottles have the caps?
No, but they are essentially capped by the surrounding cob mixture. They become pockets of air. Even if a bottle broke for some reason after the oven was complete, there would still be a cavity in the mass of cob, which is the idea - air pockets as insulation.
@@RobDuarte thanks for the time you took to answer,thanks for the video. No too many vids are as good with the real information and the time.keep it up Rob.
arent you suppose to break those bottles?
No, the glass isn't what's doing the work of insulating - it's mostly the air that it's trapping. Breaking them wouldn't be as effective.
i also thought it was meant to be broken, that way the glass retains heat and the air gaps in between the glass will still insulate, the glass is a heat sink? it should, by my thinking have insulation under the glass. having said this i havent built an oven....yet, so great vid and well done
Yes, that's effectively what's happening. The air trapped under the glass is insulating. If the glass were broken, there wouldn't be that air gap (except maybe little pockets captured by shards). -- When I was in grade school, my mom gave me a grown-up thermos (with glass containing a vacuum) on the day that she couldn't find my plastic one, and of course I dropped it. It didn't work as well after that. ;)
ok rob, i get the idea now, my mate paul said he used glass so i presumed he meant to hold the heat not to insulate. so if its for insulation my immediate thought is why not celotex/kingspan. my only thought for the glass idea is lowcost ?
Chris Hunt yes, even better than low-cost.. no-cost :) Also, I'd like to know how air compares to insulation board. I keep reading that air is pretty much the best heat insulation there is.
Amazing work... well done... yu can cook a entire lamb or pig on it
Your door hight should be 63% of over all hight to be accurate for air circulation. The sand clay mix is 1part clay 5parts sand. The outer layer is that mix plus 70% straw. Yours is way off. But the base is good
Yes this is all described in Kiko denzer's book. My door height is 63%. The clay to sand ratio was hard to determine since it was a clay sand mixture to start with. As I said in the video, I experimented by making bricks but still decided that I'd need more sand next time. For the insulation I used wood shavings from a saw mill instead of straw but the ratio is about the same. So nothing is off from what you wrote. I'd be hesitant to rely solely on percentages though .. contrary to the understanding of most people today, making things offen requires hands on experimentation/experience/judgement more than numbers. This is dirt and fire, not CAD and electronics. :)
You are way to technical ..relax build one and learn ..quit being afraid of mistakes ..our ancestors didn't put a lot of tech in those ..it's made from simple material with simple tools
This is a real Russian stove. A pipe for smoke is located in front of the entrance to the furnace
H-are-th. Hearth.
What no sound o well
+al milner there's definitely sound. Try again
Hearth is pronounced "Hahrth"
+James Edwards haha yes thank you
Very low sound
It's not too quiet, it's a little quiet. Maybe everyone watching this is surrounded by loud people and things
At 12:36 you made a oven half the size you said at beginning of project
Huh? What I'm showing at that moment is the opening for the dome, which is not the size of the oven.
Could u speak up, please!
The volume is low on this particular video. If you turn the volume up, the sound quality is good.
This video is to slow to attract me to watch all the way through...sorry
Apology accepted? 🤷🏽♂️ If you don't have the patience for the video, definitely don't consider building a cob oven. Or baking bread. Or..
Improve the voice it's difficult to understand