How to Build with Cob

Howdy, Folks. We’ve recently been working with a really cool sustainable building material: cob. It’s a mixture of straw, red clay, sand and water. And it’s really simple and fun to use. Currently we are using cob to cover the inside of our straw bale entrance and we’ve also made a bench out of cob. Want to try out cob?

Here’s what you’ll need:

Tarp

Wheelbarrow

1 five gallon bucket sifted clay

1 five gallon bucket sand

1/2 five gallon bucket straw, cut into 1 inch pieces(use scissors)

1/4 five gallon bucket water, add until all parts are fixed together and mixture is smooth

You want to mix the sand and clay first, then add in the straw and make sure that all parts are mixed as evenly as possible. Next, add the water. Start with 1/4 of a bucket of water and add more as needed. You want a wet, smooth consistency to work with.

For our cob projects, we cobbed over established surfaces. If this is what you are planning on doing, then you need to make sure that the wall or surface is clean and dry. We’ve found that the best way to start cobbing is to throw it onto the wall with some force. Then, smooth out the mixture.

You should make sure that your cob will be able to stay dry. We covered our bench with a tarp so that it would not get wet. Once our cob bench is dry, we are going to do a lime wash in order to seal the bench. The cob in our straw bale entrance will stay dry since it is protected by the roof.

Check out the links below if you are interested in learning more about cob. And please let us know if you have any questions or comments.