My First Steps Building With Earth

So today I embarked on what will most likely be a long but hopefully fruitful journey with earthen building.  I am starting out small and slow with using a adobe/cob technique to build the walls for my raised garden beds.  I will just jump right in here and say that I have taken shortcuts and done somethings just completely wrong.  For example the walls do not have any foundation to speak off but their only going to be 12 inches tall at the most so good foundations are not really a must.  I am also going to leave part of the walls completely unprotected to the elements.

I do this out of a perverse sense of curiosity of wanting to see how long it will take for the walls to break down and fall apart.  This will be a good teaching moment for me as it will give me hands on insights on what I am doing wrong when I am mixing and setting the earth.

The garden beds will be made/finished in 3 separate ways,

• Straight earth mixture shaped and applied like cob and left exposed to the elements
• Traditional cob mixture with straw or other fibers mixed into earth mixture and left exposed
• Tradition cob mixture with straw and other fibers mixed into and plastered with a earthen/lime render

Now historically the most durable will be the last one as it will have the most strength elements and protection incorporated into it.  By doing 3 separate types of building I will learn how to build with cob by making a lot of mistakes on the way.

Even though I have only been at it one day I have already learned to apply bread making techniques to cob mixing.  Making sure you have enough soil and water on hand to balance each other and get a nice stiff cob mixture that can be moved and shaped is a good way to go.  Plus even though I have a background dealing with soils I still manage to mess up this first batch of building.  According to tests I had done I had a good soil for cob build around 21% clay to 79% aggregate materials.  So I figured ok I can just go ahead and start building without adding any more aggregates.

Well I was so wrong....

As you can see in the picture despite my best efforts I have extensive cracking in my cob walls right off the get go.  This is occurring because I have to much clay and not enough sand/aggregate in the mixture, at least that is what the literature is telling me.  So now I have to start over from scratch and start testing various mixtures with more sand mixed in.

Wish me luck