Wednesday, April 7, 2010

Building With Cob

Why Build With Cob
Why build with cob?  Why not?  Perhaps the most compelling reason for me is that it doesn’t require any specialized tools or skill!  There is no industrialization involved, no manufactured parts, no need for perfection, and if built correctly can withstand the elements and the test of time.  It’s really more of an art form.  It involves curves and organic shapes; which are being proven to be more beneficial to the human spirit than straight walls and corners.  The fact that your finished piece or art is a building is just gravy.  Top that off with the fact that you literally get to work with the earth, recycle stuff, and spend less money than you would on conventional building methods… well, that seems right up my alley! 

My cob Building Journey Starts Here
Yes I am embarking on a journey to build with cob.  I’ve decided to start small, with a shed.  Though there is plenty of evidence to suggest that a full size house of great form and function is possible, I figure in order to taste success and gain some experience, perhaps I should start small.  I am quickly finding that this was the right choice for me, as there is quite a lot to consider when building with cob.  I think the simplest, easiest to read basic guide is:  The Cob Builders Handbook: Hand-Sculpt Your Own Home

The Design
Like all building, before anything happens, you must have a plan.  A poor plan and everything else becomes exponentially harder.  Cob building rely on curves and a simplicity of form blended with function, not straight walls and corners.  Chapters 6 and 7 of  The Hand-Sculpted House: A Practical and Philosophical Guide  are phenomenal resource for design planning.
Here is where I am planning to build my shed.  (Provided there are no buried utilities.) It is roughly a 9’ x ’14 foot area up against the deck.  My original plans are calling for a rocket stove built into the south wall.  My wife and I like to sit outside at nights and during the winter I though it might be nice to have a little “bun warmer” built right in. I’m keeping the design pretty simple except for the stove and bench.  I figure it will be good practice if I ever decide to build on a grander scale.

The Ingredients
The ingredients for cob are quite simple; sand, clay, water and straw.  I’m reading that the best mixture has between 30-50% clay.  The sand gives it form, the straw gives it tensile strength, the clay sticks it all together, and the water allows it all to mix up and be formed as you wish.  My original plan was on less suitable ground I think, so I am making a few test bricks to see how the soil in my yard compares.  I am hoping to find a decent mix that doesn’t require me to go find ingredients elsewhere. 

Cob is the brother of Adobe.  Adobe is the same ingredients formed in to bricks that are then used to build structures.  Cob is monolithic, in that the ingredients are literally “piled on”, forming one solid mass of structure.  The most interesting part is, that even with its simplicity, buildings made of cob outlasts building made with many other materials.  There are cob building in England and elsewhere that have been constantly inhabited for nearly 1000 years.     
Other Considerations
If not protected properly, cob is prone to rapid erosion.  So cobbers call it “giving it proper boots and a hat”.  The foundation is the boots, and the roof is the hat.  Without a solid foundation and a well designed roof, all of the building efforts won’t be worth…. Well, the effort.  Then there is the issue of electricity and plumbing, which, I’ve managed to forestall for now by building a simple shed.   

Stay tuned and Follow my Experience
I will share my experiences with you.  There will certainly be much to laugh about, and probably some to cry about.  Perhaps it might encourage some of you to give cobbing a go in the future. 


  1. This is absolutely fantastic! The science person in me loves the experimentation. The Earth person in my just love the idea of making an earthen structure. Keep writing about it. Great blog!

  2. Science, earth, art, philosophy, joy, laughter, knowledge.... they all kinda go together don't they?