Materials hildecobinsnow

Published on September 12th, 2008 | by ziggy

75

Natural Building 101: Building a Cob House

hildecobinsnow

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



  • http://dancingrabbit.org Liat

    I heart cob! your house is awesome!

  • http://dancingrabbit.org Liat

    I heart cob! your house is awesome!

  • http://www.naturalbuildingnetwork.org Jack Stephens

    Great article! Please check out http://www.naturalbuildingnetwork.org for more resources including cob workshops offered around the world.

  • http://www.naturalbuildingnetwork.org Jack Stephens

    Great article! Please check out http://www.naturalbuildingnetwork.org for more resources including cob workshops offered around the world.

  • http://summerjuice.net/ Summer

    Amazing article! Really inspired me to try and build something with cob..

  • http://summerjuice.net/ Summer

    Amazing article! Really inspired me to try and build something with cob..

  • Charles Eaton

    How do you power the cob house?

  • Charles Eaton

    How do you power the cob house?

  • http://www.small-scale.net/yearofmud Brian

    Hi Charles:

    I have a power switchbox installed in the cob, along with one interior and one exterior outlet. I can get a power hookup to some solar panels or a wind turbine through this switchbox – however, I’m planning to go without power, initially. I want to experience whats it’s like to live without it.

  • http://www.small-scale.net/yearofmud Brian

    Hi Charles:

    I have a power switchbox installed in the cob, along with one interior and one exterior outlet. I can get a power hookup to some solar panels or a wind turbine through this switchbox – however, I’m planning to go without power, initially. I want to experience whats it’s like to live without it.

  • http://www.squidoo.com/coffea cchiovitti

    I’m really drawn to the design of the top photo. It’s charming and just looks like someplace that would be so cozy and inviting to live in. I’m so tired of cookie-cutter housing developments littering our landscape.

  • http://www.squidoo.com/coffea cchiovitti

    I’m really drawn to the design of the top photo. It’s charming and just looks like someplace that would be so cozy and inviting to live in. I’m so tired of cookie-cutter housing developments littering our landscape.

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  • http://motivatingmessages.ning.com/ PParham

    Not sure they are considered Cob houses or if the exact same materials are used but this type of housing is pretty much standard living in Peru. The cooperation of the neighbors helping each other was amazing.

  • http://motivatingmessages.ning.com/ PParham

    Not sure they are considered Cob houses or if the exact same materials are used but this type of housing is pretty much standard living in Peru. The cooperation of the neighbors helping each other was amazing.

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  • Jason

    Hi Brian,

    I’m interested in building a cob house in Ecuador. Do you know of anyone who has done so in this area of South America? I would love to know what the soil composition is like so I can decide for sure if this will be the best local material to work with.

    I would like to build with as little financial outlay as possible.

    Nice website!
    Jason

  • Jason

    Hi Brian,

    I’m interested in building a cob house in Ecuador. Do you know of anyone who has done so in this area of South America? I would love to know what the soil composition is like so I can decide for sure if this will be the best local material to work with.

    I would like to build with as little financial outlay as possible.

    Nice website!
    Jason

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  • http://www.small-scale.net Brian Liloia

    Hi Jason:

    Unfortunately, I don’t know of any cob houses built in that area, although I’m sure with some research you can find out. I can almost guarantee that it’s possible to build a house in this style in that area. Good luck.

    – Brian

  • http://www.small-scale.net Brian Liloia

    Hi Jason:

    Unfortunately, I don’t know of any cob houses built in that area, although I’m sure with some research you can find out. I can almost guarantee that it’s possible to build a house in this style in that area. Good luck.

    – Brian

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  • Marilyn Nelson

    We also Live in MO,and are wanting to build a cob house. Where do we find a place to buy good clay? We are in SW MO.
    Marilyn Nelson

  • Marilyn Nelson

    We also Live in MO,and are wanting to build a cob house. Where do we find a place to buy good clay? We are in SW MO.
    Marilyn Nelson

  • kathi kaufmann

    hi, i did a cob fireplace with clay, sand, straw and water, but since i have clay in the subsoil where i dug out my swale i was wondering if subsoil, straw and water would be a better combination. do you have a preference? this would be for a cob oven, btw.

  • kathi kaufmann

    hi, i did a cob fireplace with clay, sand, straw and water, but since i have clay in the subsoil where i dug out my swale i was wondering if subsoil, straw and water would be a better combination. do you have a preference? this would be for a cob oven, btw.

  • dwight edmondson

    i want to build my own natural house,or get some help from someone who has experience in building a natural house or cob house.i want a nice kind of big house maybe like 4 to 5 bed rooms..please someone give me more infomation on how to accomplish this.

  • dwight edmondson

    i want to build my own natural house,or get some help from someone who has experience in building a natural house or cob house.i want a nice kind of big house maybe like 4 to 5 bed rooms..please someone give me more infomation on how to accomplish this.

  • http://reservanaturalvictoria.blogspot.com David Rivera

    I am not expert, but I am building a dream as you
    No soy experto, pero estoy construyendo un sueño como usted
    David

  • http://reservanaturalvictoria.blogspot.com David Rivera

    I am not expert, but I am building a dream as you
    No soy experto, pero estoy construyendo un sueño como usted
    David

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  • http://profiles.google.com/ackiener Andrew Kiener

    There’s a very good chance you won’t have to buy the clay at all. Keep searching the internet for how to do a “jar test” on your soil – basically, you shake up some small soil samples in a jar, and the various components of the soil – sand, clay, and organics – will settle out into layers over a couple days. This gives you a rough idea of how much clay is in the soil, and in most cases there’s enough clay to just use the dirt under your feet mixed with straw and maybe some extra sand. That’s part of the beauty of cob – less to buy, less to haul.

  • http://www.modularhomesnetwork.com/ Modular Homes

    Yes! Excellent writing, continue to keep in place the awesome job.

  • Dan Boxman/Uncle Danny

    Google the Last Whole Earth Catalog. The Shelter Book. Sun Ray Kelley. Strawbale. Cordwood construction. Communes. Radiant floor heat. Yurts. Tipis. Geodesic domes. Hempcrete and Ferrocrete and Monolithic construction. Put that in your pipe and smoke it.:D

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  • Diane mccleland

    could you build an earth sheltered cob house.  i love your little house it looks like something from a fairy tale.

  • Mike Dearborn

    When I read ‘flue pipe through a cob bench’ I immediately thought, “Dancing Rabbit had one of those.” Then I read that you are in fact talking about Dancing Rabbit! I visited once and I thank you for being very welcoming people.

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  • curious

    Although I understand that MO building codes are not as stringent as in other states, I am wondering what loopholes you used in order to build the cob house. Do you have a primary residence on the property with access to power and plumbing, thus allowing you to build the cob structure as a “structure” rather than a “house”?

    I sincerely want to live a lifestyle that allows for complete sustainability (rustic) void of electricity and plumbing, even if that means I move to another state. I may be misguided, but after having looked up the International Building codes for all of the states(federally), cob housing seems to be illegal in any state. Is cob construction subjective in the law, based upon who you do or do not know? Or maybe based upon loopholes or educated terminology? What about zoning or property type?

  • http://www.glennrileymeyers.comorhttp://www.ourgreenstreetsblog.com Glenn Meyers

    I would start by contacting these entities from the post: “the Cob Cottage Company and House Alive!, both based in Oregon are two companies that regularly host workshops, internships, and work parties. For reference on methodology, I would remind code people of adobe construction.

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  • Alin

    Hello I’ve got a question,
    We’ve got an abundance of dead beach grass on our sandy beaches. Can that grass substitute for the straw?
    Also, are there particular sand sizes that work better than others?
    Thanks

  • http://www.glennrileymeyers.comorhttp://www.ourgreenstreetsblog.com Glenn Meyers

    I’m not an expert – see if you can locate the author to ask.

  • Trevor Walter

    I’m building a cordwood house and using cob as the mortar between logs. I’ve got my mix figured out but I’m wondering if I can use a cob/lime mix to build my foundation? The foundation will be approximately 20″ wide.

    Any thoughts / ideas are greatly appreciated!

    Thanks,
    Trevor

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  • Zdenek Pokorny

    Howdy!
    It really inspired me just a short time ago. I´ll try to do it on my land. To build such a house.
    Have a nice time!
    Mr Zdenek Pokorny, Jicin, Czech Republic

  • http://sustainableforafuture.com Ji

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

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  • Melanie

    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!

  • http://sustainableforafuture.com ji

    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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  • Mary

    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?

  • Mary

    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…

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  • Bob

    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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  • Lynne

    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)

  • chant

    I just found land… which clay do I need, there is so many ? do you have a specific name for it ? thank you

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