Cob Mixing and Application Basics – “Cob Cottage Company” Natural Building Apprenticeship at Spirit Pine Sanctuary

The approximate area of the house we are constructing is 550 sq feet. We have 20 days and 15 not-so-experienced people to get the walls up and to put a roof on it (well, at least set up the ridge beam). Will we make it?

First few days are spent on getting familiar with the cob mixing process. In theory, it’s pretty simple.

  1. We place the dry materials (soil, clay and sand) on a 8 x 10 ft tarp and roll it by pulling on the corners
  2. Then we add water to the mixture and roll it again
  3. We stomp the mixture with our feet until it’s evenly moist and mushy. “Mud dancing”, we call it.
  4. Final step is to add straw, roll it again and dance on it until all straw is integrated

In practice it turns out to be pretty simple as well. If the mix comes out too wet, add a bit more soil and straw. If it’s crumbly, add clay. The material is very forgiving, and there really isn’t “the right” way to mix it. As long as all the materials are integrated into a malleable mix, it’s ready to be applied.

This is our process.

First we take soil samples to create some test cob bricks. Will they crack or be strong like a rock?
We start by taking soil samples to make test blocks. Will they be rock-solid or crack?

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