Building a Rocket Stove: Part 2: Cob Bed and Bench

by ziggy on April 27, 2009 -- 13 comments -- Follow

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UPDATE: Unfortunately, this rocket stove design has proven to be a failure, and I have since deconstructed the stove. I cannot recommend that someone follow these plans. You can read my original post below for what not to do, though.

The rocket stove and cob bed and bench are essentially finished. The rocket stove (which I will detail more in yet another post) has 25 feet of horizontal run that wraps through the bed, into the bench, and out the southern wall of the house.

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Laying out the flue pipe

Before making the cob bed, I laid out the stove pipe and propped it up on pieces of urbanite and brick, and then I leveled it. I sealed the joints with aluminum tape to help keep everything together. After I decided that the stove pipe was level, I started adding rubble (pieces of urbanite, brick, stone, and old cob) to the bottom of the bed, underneath the pipe. I wanted to add as much filler as possible to avoid having to make that much extra cob.

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Sculpting the cob bed

Next, I began making cob and sculpting the bed. I used a ratio of three buckets of sand to two clay, with a slightly lighter amount of straw. (Sand provides the heat storage capacity of the mass, versus the clay which just binds the material together.) Along the wall, I stuffed some light clay straw (straw lightly coated in a clay slip) to help create a kind of insulation buffer between the bench/bed and wall. I cautiously cobbed around the three ash cleanout holes so that the lids could be easily removed and my arm maneuvered into the pipe.

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The bed and bench took something like 20 batches of cob to complete. (That’s almost 1/10 of the material it took to build the house itself!) Surprisingly, it was pretty quick work. I kept the rocket stove burning to help dry the mass out as I added new material. The bed half has about six inches of cob on the pipe, which is quite a bit more than I would have liked, but it needed to be that high to meet the top of the T joint cleanout. The bench has about two inches of cob on top of the pipe.

Miso storage under the bed

Alongside the bed, I carved out two storage nooks. I sized the nooks to fit a five gallon stoneware crock so that I could keep fermenting foods warm while the mass is heated. (Fermented foods like miso like warmer temperatures.) As you can see above, the pipe is very close to the back of the storage nooks. (Might this be the first bed with miso storage built into it?)

The cob bench

The cob bed tapers into a bench that curves around the south and west walls. This little sitting area could probably seat about four or five people. I’ll get a table in there to make it more of an inviting hang out space. It might make for a nice place to sit and eat meals or play board games, especially.

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Of course, the bed and bench will get a final plaster treatment once it’s all dry. Eventually, my plan is to make either a homemade wool or straw-stuffed mattress for the bed half of the mass. I am definitely excited about sleeping on this thing…

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dominic ebacher April 28, 2009 at 9:48 am

Great job! When do you get to fire it up?

Joan April 28, 2009 at 3:14 pm

That looks sweet! I guess that’s what you were working on when I saw you mixing cob the other day.

Oh, and thanks again for the peppermint! A few of the cuttings are doing well. I’ll probably come by for a few more, so long as you really want it gone.

Matt May 1, 2009 at 6:10 pm

Can’t wait for more. I found this blog today and have just completed reading it. Whew! Thank you for the extreme detail. Very enjoyable.

jesse June 9, 2009 at 4:57 pm

hay nice site buddy lol i can actually impress my teachers with this one

Tony June 10, 2009 at 7:32 pm

Great stuff, gimmie more I tells yeah!

Gritty Pretty August 11, 2009 at 1:49 pm

Beautiful process and gorgeous finished product! I especially love your nooks for fermentation! What a great idea!!

amy September 27, 2009 at 5:58 pm

hi.

your home and eco ideas and methods are great. I’m looking for land currently so i can build a cob home :) and live the dream of being self efficient

amy

william November 6, 2009 at 7:08 pm

My partner has about three hectares of land with a stream running through it. It’s comprised two hectares of wheat field at the moment and one hectare of woodland.
I’ve told her about straw and timber construction and she is interested in doing it. I have no cash and hers is tied up in a little flat which her aunty left her recently when she died (as was the land I mentioned).
What costs over and above the free materials that come with owning the land would there be to build a self sufficient home do you think?
We are both actually relatively poor despite having this gift of land so cash is the big problem. Actually, I’d love to escape the cash economy as much as I possibly could hence the desire for living moer naturally off and on the land – as it were.
Best wishes.

ziggy November 6, 2009 at 7:23 pm

Hey William:

Well, it sounds like you have access to some resources on-site, which is a great start. But it’s impossible to say what a house would cost to build. There are so many variables – size, materials, design, etc. People have built for next to nothing, others have spent tens of thousands of dollars. If you are resourceful and can obtain most of your materials for free, and have a lot of time or many friends that can help you to build, the cost should be relatively cheap. Be creative!

Good luck…!

john March 6, 2010 at 10:58 pm

If your barrel isn’t getting hot, perhaps it is too high from the heat riser. Most videos and information read tells me you want 1 and 1/2 inch of clearance. 2 inches of clearance would bring the majority of the heat to the middle of the barrel, 1 and 1/2 inch of clearance should bring it to the top of the barrel. Also, with your complaint I need to ask, is your heat riser insulated? if not, that would be your best reason for your problem. Best of luck, JOHN

Subcomandante Lorax September 12, 2010 at 1:05 am

This looks awesome! Great job.
I linked this page on my blog about living permaculture (primarily at the Bullocks Permaculture Homestead). The article was about the energy tour we do on our site during the PDC with some examples of rocket stoves. I think I also saw you on an article on Yes magazine recently. ah, cob cob cob cob cob…..

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