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Published on September 12th, 2008 | by ziggy

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Natural Building 101: Building a Cob House

cob house

This year, I started building my very own cob house. Cob is an extremely environmentally-friendly natural building material composed of sand, clay, and straw, and it has withstood the test of time and the elements over many past generations all over the world. Haven’t heard of it? Then read on to learn more about this creative, beautiful, and highly ecological building process.

What is cob?

Cob building dates back hundreds of years ago, and cob houses built over 500 years ago in Europe are still inhabited to this day. That’s pretty dang impressive considering the simple nature and composition of the material: buckets of wet clay and sand are mixed by foot (or by horse, oxen, concrete mixer, or even Bobcat excavators) and then combined with straw to produce a sticky, malleable material that can be rolled into palm-sized loaves (or “cobs”, which is where the name originated) and then laid onto a foundation and sculpted by hand to build thick and massive cob walls.

The properties of cob

Cob structures are monolithic: layers of material are worked together to produce one massive structure, compared to something like adobe, which is typically made into forms that can be stacked like bricks. When cob dries, it resembles rock or concrete in its hardness. With a nice thick coat of plaster, cob can withstand significant weathering before it starts to (slowly) wear away. Exterior cob walls can range anywhere from over one to three feet thick: the thicker they are, the more heat they are capable of storing. You see, cob is not very insulative, compared to say, straw bale buildings. Cob has better “thermal mass“, which means it is capable of capturing and storing large amounts of heat. The best way to do this? Stick a flue pipe through a cob bench and heat up your furniture with a rocket stove.

Cob: beautiful and environmental

The main components of cob building – sand, clay, and straw, come directly from the earth, oftentimes right beneath our feet. (For example: all of the clay I am using in my cob house comes straight from the soil on the property here at Dancing Rabbit Ecovillage.) Therefore, cob has very low embodied energy, meaning there is little energy wasted in manufacturing and transporting materials over great distances. Call it a “local and organic” kind of building technique. Not only that, but it’s beautiful, too: cob lends itself to smooth and curvy home design, with rounded doorways and curved walls. Shelves and storage nooks can be built directly into walls.

Cobbing is simple and cooperative

Cob building is intuitive and requires little to no experience and no heavy machinery. People of all ages can easily start mixing material and “cobbing” together, and gain a basic understanding of the building technique. It’s definitely a labor-intensive process, so it benefits from large groups of people. (I’ve worked with up to ten people at a time and it’s nothing short of a party!)

Where to learn more about cob

Fortunately, I live in Missouri, where there are no building codes to prevent me from building with cob. Unfortunately, you can’t just go ahead and start building your own cob house without a bit of meddlesome bureaucracy in most states. However, there are plenty of great organizations where you can at least get your feet dirty and starting making cob: the Cob Cottage Company and House Alive!, both based in Oregon are two companies that regularly host workshops, internships, and work parties.

There’s many a reason why cob has been around for as long as it has, and why it’s used all over the world. It’s inexpensive (economically and environmentally), beautiful, and well, quite simply “natural”. Cob is what truly “green buildings” are made of.

(p.s. Please learn more about sustainable building jobs here!)

(Image credit: cobworks.com, humboldt.edu)




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About the Author

I'm a 26-year-old currently living at Dancing Rabbit Ecovillage in northeast Missouri, an intentional community devoted to sustainable living and culture change. Things you might find me doing here (other than blogging) are building with natural materials, gardening, beekeeping, making cheese, candlemaking, and above all else, living simply. You can read about my on-going natural building projects at: http://www.small-scale.net/yearofmud



72 Responses to Natural Building 101: Building a Cob House

  1. Ji says:

    Hi, Can you tell me, do you need to build a foundation before you start your cob structure?

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  7. Melanie says:

    Hi, I also live in Missouri, SW mo and i just bought 9 acres that I am considering building an earth bag or Cobb homE. From what i read earthbag has some time benefits but i am a woman and they are very heavy. I’m wondering if you ever finished your Missouri cob home and what kind of roof you used? Also any problems with the rain and snow with the structure? Also, any resources that you could provide me locally including anyone knowledgeable that could oder help, any cheap places or resources for information, such as anyone familiar locally who can offer Insight advice. I would love to hear from you. You can email keepnit2gether@yahoo.com. Thanks!

    • ji says:

      hey, i haven’t even started the cob yet, though honestly i think it is a good choice for this area because of the heavy clay in the soil. i think that the most important thing when considering the roof is something that you can tie into the foundation so that it is secure. i might be building a small cob structure soon if you wanted to come by and see it or help in the the process to get an idea of how to do it you’re welcome to. let me know.

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  9. Mary says:

    I live in mid Missouri! (wonderful state, great place to grow up like I did) anyways I live right near the big muddy and was wondering about suggestions/workshops in the area? or perhaps someone locally who’s made one that I can visit… Any suggestions?

  10. Mary says:

    Can Cob houses be made to be earth contact? Is there a way to hybridize with other natural building methods to do so? If so which is the best for Missouri especially close to the river (I also live her, go tigers!) What about the possibility of using some kind of glaze to water proof like you would pottery? Just spitting ideas here…

    • Bob says:

      Mary, I’d suggest having facia such as stone and a roofing material like barrel tile on hand as the cob walls go up and apply the facia and roofing from the ground up as you build while the mud’s still wet; cedar logs can also be set in the cob wall(s) as headers, joists or anchors for wood or gypsum facia.

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  14. Lynne says:

    I live in Jefferson Co, Mo and it seems no matter the amount of land you have, going off grid in this area is way harder than it should be. So many, what you can build and what you cant build. I figure if it is my land? why can’t I do with it whatever I wish? So much for freedom. I was looking at 45 acres, but once I told the seller that I wouldn’t be using the utilities – his reply was why do you think I am selling it? Seriously. If you build a hunting cabin on your land, it has to be so big, and only occupied for so many months out of the year, etc… An outhouse or something like that no matter if you are 20 acres deep in the 45 acres , you still are restricted., Pathetic! I don’t think there is a place in America where you are truly “Free” anymore. If anyone knows of a area in jeffco where you can build a chicken coop with out a building inspector, email me. lynnstl29@yahoo.com (i was joking about the chicken coop thing- but give it time, they will have some regulation against that too)

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