How to fix a Rocket Stove

Brian (a.k.a Ziggy) recently reported on his blog that his rocket stove is not working. This is a handmade masonry heater he built by hand from cob, firebrick, and steel. It’s a very clever design that has the flu flowing through the cob bed platform. The problem is that it doesn’t draw unless there is a bit of a wind outside. His cob house is located at the Dancing Rabbit Ecovillage.

I took a careful look at all of Brian’s photos and pulled all my old kiln building notes & memories out from my past as a potter and came up with a modification to his design. I’m not sure he’s game to give it a try, but I suspect it would work better with this modification.

Basically I’m simply suggesting that he digs into the cob a little  and connects the stove to the rear exit pipe leaving the other two pipes (white) burried in the cob and disconnected from the system. This would make it much easier for the air to flow because there are fewer turns and less horizontal pipe. My other suggestion is to experiment with a taller chimney.

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A Cob House You Can Build

Ziggy’s cob house at the Dancing Rabbit Ecovillage is complete. He’s also posted a lot of detailed information about the construction process, cost, and sweat-equity required to build such a house on his Building a cob house blog. The house is about 200 square feet and includes a reciprocal roof and rocket stove. Ziggy estimates that it took about nine months of full-time work to build the house. His total cost was about $4000 but $1000 of that was labor so you could actually build this house for $3000 if you did all the work yourself. Take a look at Ziggy’s cob house, aka GOBCOBATRON.

Photo credit Ziggy.

A Closer Look at Tiny Cob House Construction

Cob is earth, sand, and straw. It’s similar to building with adobe but instead of making blocks to stack-up like with an adobe house, cob houses are built-up while the mud is wet. The material is essentially the same, the construction process is what differentiates cob from adobe.

The most obvious design difference is that adobe homes look more square and cob homes look more organic and sculptural. This is due directly from building with mud when it’s dry (adobe) versus wet (cob). Theoretically you can achieve a similar aesthetic with both methods but cob’s natural tendency is to look much more organic and free.

Brian Liloia is building a tiny cob house at the Dancing Rabbit Ecovillage in Missouri. Last summer he finished the walls and roof. His house has several very interesting design features like a reciprocal roof, a rocket stove, and earthen floor.

The reciprocal roof is a self supporting round roof that’s often made from thin logs that are then fastened together and covered with a more weather proof roofing material. Cob and adobe homes need a good roof to keep the water off their earthen walls.

The rocket stove is a built-in earthen stove with a long flu that snakes through the cob walls and built-in benches. Adobe and cob provide a great deal of thermal mass so that once you heat it up, or cool it down, the temperature of the room is maintained by the mass of the building. The rocket stove in Brian’s home should keep it very warm through the cold Missouri winters and cool in summer so long as he doesn’t light too many fires.

Sealed earthen floors can be very comfortable to walk on and surprisingly clean. They require careful cleaning and will eventually need resealing but they are a far cry from what you might imagine a dirt floor to be like to live with. Linseed oil is often used as a sealer.

Below are some photos from Brian’s blog. He’s documented his design choices and progress in great detail with photos. Visit Brian’s blog to learn how to build a cob house. For more about building with cob visit I Love Cob. There are also many good books on building with cob if you’re serious about building a cob house in the future. One good book on the topic is Building With Cob: A Step-by-step Guide. Photo credit Brian Liloia and friends.