Thursday, August 7, 2014

What is cob?

It was originally our plan to buy a piece of land and build a house on it. We wanted to build a house that had a low cost, was made out of natural materials, and that would be possible to build ourselves.  Because of these reasons we were set on building what is known as a cob house.
A cob house with a live roof

In short, a cob house is made out of sand, clay, and straw. The materials are all mixed together when wet and then put together in a desired form (wall, fireplace, etc.) to dry and harden. It is a natural analog to concrete. Whereas concrete is made with sand, cement, and steel; cob is made with sand, clay, and straw. The sand makes up most of the mass in both cob and concrete, the clay/cement acts to bind the sand together, and the straw/steel  provides tensile strength. The upside to concrete is that it is waterproof. If you made a sidewalk out of cob it would turn to mud after the first rain. The upside to cob is that it circumvents the need for cement factories which are one of the largest contributors to greenhouse gas emissions. A good roof is all that is needed to protect a cob wall--even in the temperate rain forest of Oregon.

We wanted to build out of cob not only because it is natural, but because we think cob houses can be very beautiful. Cob walls can be curved and sculpted into many different non standard forms.
Yulia standing by a garden wall

The foundation for a cob house is quite simple. The kind Yulia and I learned about during a seminar at the Cob Cottage company is known as a rubble trench foundation. It’s pretty much what the name implies--a trench with rubble in it.
A rubble trench. The pipe is for drainage.

A stem wall is then placed on top of the rubble trench foundation. It can be made out of brick, stone, or even broken pieces of sidewalk.
A stem wall made out of old concrete slabs

You then mix up the sand, clay, and straw and put it on top of the stem wall. 
An unplastered cob wall in the making

One way of doing this is to make balls out of the wet materials and then make a monolithic wall ball by ball. The balls are also known as cobs (from Old English meaning a lump or rounded mass (according to The Hand Sculpted House)) and should ideally be about the size of a cobblestone.
The "Laughing House" at the Cob Cottage Company in Oregon

One of cob’s more well known cousins is adobe. To make adobe you mix sand, clay, and straw and put it into forms to make bricks. You then sun dry those bricks, stack them to make a wall, and add plaster.
A centuries old adobe building in Taos, New Mexico

This blog post just scratches the surface when it comes to cob. There are many nuances, skills and tricks to know when building with cob. Many books and websites can be found on the topic. Probably the most comprehensive text on cobbing is The Hand Sculpted House. I say this because it is not only a good how-to book, but also because of the authors’ personal philosophy which comes out in the writing:
Congruent with developing an essentially new construction system and a gentler approach to creating buildings, we have attempted to manage our individual and collective lives in a manner consistent with our values. All of this needed to be reflected in this book, otherwise none of us would feel honorable. In committing to publication we must take responsibility for every tree that was cut to make this paper, the fuel for transport, chemicals in printing, and the seemingly inevitable toll of tiny lives that are extinguished by commerce and industry. We hope this book is valuable enough to more than offset these costs. The dividends in changes of attitude, creation of more opportunities for ecological buildings, and diminution of environmental damage all need to be great, or we have merely contributed to the problem. So, borrow a copy if you can (ask your local public library to order it) or if you can’t, buy a copy for your library to lend out, knowing that this way you can read the book whenever you want. [quoted from the introduction]

I quote at length here because I feel this is one of the most important passages from the book, and, if you haven’t noticed, it hardly addresses the topic of cobbing at all. The authors include themselves in the text as whole people, not just as experts in cob. They outline their personal philosophy which supports their promotion of cob and the writing of the book. Although Yulia and I are not as eloquent as the authors of The Hand Sculpted House, we feel similar about our blog and our little project of moving to a small village in Ukraine.  

We realize that our blog is not ecological in the strictest of terms. Our laptop was made by exploited workers using plastics and rare earth minerals mined by people who also suffer from appalling working conditions. We use non renewable energy just to write and store our blog of the internet. Also, you could look at a picture of me mixing cob and criticize me for wearing a bathing suit made out of synthetic fabric. We just had an asphalt shingle roof installed on our house.

Yulia and I hope that you can see past the compromises that we make and notice that we are doing our best to move in a certain direction. We make no claims be at the end point and have "all the answers." We write this blog to share what we think is valuable information and a valuable philosophy. Use your mind as a filter. We hope that you find at least some use to the things we talk about so that the compromises that we have made have been worth it. The cement industry is one of the largest producers of greenhouse gas. Even if we have convinced you to use clay in lieu of one sack full of cement, it's a move in a positive direction.


  1. Thank you for this interesting peek at cob and at some of your personal philosophies :) How funny that you mentioned Oregon, small world!

    Did you end up building an entire house out of cob or are you using it to patch things up here and there?

  2. We're just using it to patch things up right now, but we have plans to build an entire building at some point in the future.

    We've been to Oregon twice--once for the cob course and a second time to work on a farm for several months. It's a lovely place!