Building with Cob

A few years back I joined a group of people doing a 'cob' workshop on the edge of a beautiful volcanic lake in Guatemala, which I recorded and posted on Youtube.
The video is in Spanish but it now has subtitles in English and it provides a good introduction to the technique.

Cob is a traditional building technique that uses earth/clay mixed with straw to build or sculpt walls in flowing, smooth forms.

Image Source: Unknown (Pinterest)

Image Source: naturalhomes.org

The great thing about cob is that the raw materials come directly from the site making it environmentally friendly, fun and cheap.
The downside is that it requires a lot of labour - but often people organise cob parties in which people come and work for free (kind of like WWOOFing) in order to learn...and play with mud. All the owner has to do is provide food, drink and sometimes accommodation.

At the workshop we participated in, people paid to work but we all had a great time, made new friends and learnt a lot.

A more common technique in this part of the world (Central America) is adobe, which also uses mud and straw but in the form of sun-dried bricks. Cob however creates one continuous mass making it very strong. People may think that earthen walls would be washed away by the rain, but there are cob cottages in England 500 years old and there is no shortage of rain in the U.K.

Image Source: http://www.cobcottage.com/ancient-cob-building-devon-england-date-plate-reads-1539

The trick is "good boots and hat", the boots being a stone (or any other suitable waterproof material) foundation so that the cob is never touching the ground...

Image Source: http://strawclaywood.com/natural-building-techniques/masonry-and-foundations/

and the hat being a watertight roof with a large overhang. This way water very rarely reaches the wall.

Image Source: Unknown (Pinterest)

I wasn't there long enough to see the completion of the project, but I would love to go back and record an update when I get the chance.

The following text is from cobcottage.com and comes from a paper read by Ianto Evans, (one of the authors of The Hand Sculpted House) at the 2009 Summit on Climate Change in Copenhagen.

In the United States, it’s estimated that half of all energy use goes into buildings, the majority of them houses. In housing, natural construction can probably save 50-80% of this energy, so in terms of low-hanging fruit, these apples are right there at basket level.

Natural Building offers a number of strategies and principles that, when applied on a large scale, will drastically reduce the amount of carbon emissions associated with construction, heating, cooling and maintaining houses. Here are some of them in brief:

1. Use of local materials, minimally processed

The local foods movement is in full tilt. We’re understanding the implication of buying corporate apples from Chile versus pruning our own apple trees. As for building materials, what’s the sense in hauling away your local trees to a distant sawmill, then buying back inferior standardized products at half the strength and ten times the price? Do you really need to bring bricks from giant factories hundreds of miles away when we have earth to build with right here in the backyard?

1. Earth, the main material, is abundant world-wide, long lasting, reusable indefinitely

We know how to use earth to make beautiful strong walls, floors and plasters. Cob houses in England are still lived in after 800 years. In the Middle East, there are earthen buildings 3,000 years old. Most of China’s Great Wall is earthen constructions and is doing well after millennia.

1. With durable construction, no need for early replacement

Wood-frame houses with fiberglass insulation and sheetrock walls typically fall apart in a few decades, then there’s the cost, both budgetary and environmental, of rebuilding or replacing. Earthen buildings can stand for centuries with hardly any repairs. If the average wood framed house is in good shape for even 50 years and the cob equivalent for 500, over time the ecological cost of sustainable buildings in only one tenth of the alternative, even assuming no other savings.

1. Build gloves, not boxes. Smaller buildings have less heat loss, less maintenance, less everything

We don’t clothe ourselves in boxes, why try to live in one? Wrap the buildings around the use, as knitted socks fit your feet. A tight fitting building can be much smaller, and a curved (not circular) space feels roughly twice the size of one with square corners and straight walls. If we could do only one thing to cut global warming it would be to live in smaller homes that fit us better.

1. Observation of nature tells us what will work well

Building that accommodate natural principles will last longer, need less maintenance, create less pollution, and use less energy. Nature has 10 billion years of slow experimentation to arrive at what works well. We can learn from her. For instance, she never repeats anything; if every daisy in the field looks identical, we’re not looking closely enough. She makes almost nothing square or straight. Could it be that humans discovered a geometry of frailty? Also, geological materials outlast biological ones.

1. As a movement it can model non-consumer satisfaction, by making not buying

Building your own shelter effects a paradigm shift for almost anyone. The awareness and self-confidence it creates overflows into other parts of our lives such as what food we eat how we spend our time. We’ll now enjoy other home-based activities – playing games with the family, making clothes instead of buying them, perhaps even starting a home business. No more commuting means one less car.

1. Management by personal skills and observation, not by automation

Living in a natural house implies being engaged in its management, deciding when to open the curtains, let in fresh air, or make more heat by burning wood we cut, split and stacked ourselves. We get basic satisfaction from these primary atavisms, involving us daily in Nature’s cycles. Re-focusing our attention at home has many side-benefits, from strengthening family relationships to decreased consumption.

1. Natural Building builds a network of resistance to compulsory consumption

As corporations gain more control of our lives, restrictive laws force us to consume more, over our own reluctance. Building regulations ensure that legal construction is overbuilt and very expensive. Well-intentioned consumers get trapped in a maze of insurance, taxes and fear of prosecution. Almost by definition, consumers are isolated. Yet because Natural Building is a social activity, it quickly creates networks of like-minded independents who gain self-confidence by being part of the movement. By sharing stories and strategies, we understand our rights and options better. Together we can stand up to societal manipulation.

1. Older industrial societies model the advantages of traditional building

China just gained the distinction of being the world’s biggest polluter, as a fifth of the world’s people fight to own a personal car, to eat meat daily and to buy plastic throw-away junk. Most of the world now aspires to a big concrete house with a giant TV. Who taught them? For decades, though media and international “aid” Americans have projected the American Dream as the only worthwhile goal. Even if some of them hate us, many of the world’s people still look to the US for models of how to house themselves. But 8 billion people living in US-sized houses will commit us all to starvation. It’s time to model high-profile ecological buildings that work better and cost less than the industrial throwaways. We already have their attention so now let’s project a sustainable, joyful model for the rest of the world to emulate.

1. Natural Building attracts attention because it is a public performance

This field has been shown to grow exponentially, autonomously and democratically. Almost anybody building with earth attracts helpers. People just passing by join in because it looks like fun. From small beginnings only 20 years ago, it has now become a worldwide movement. Reasons for its success? The techniques are simple; in a couple of weeks you can learn to build your own home. Then you can teach that to other people and they can teach others. Also, natural builders are manifestly having fun. They’re inspired partly by the cooperative, friendly, humorous approach. The most unlikely people become aficionados at their first exposure, bubbling with excitement. But who ever feel in love with concrete blocks?

The internet is full of great articles and videos on the subject, I hope this has whet your appetites to learn more!