Cob: An Ancient Building Tradition Reborn

A pic and video slideshow of the workshop I attended. And loved. To see a cob house being built by the instructors, Sarah and Jared (as well as other natural builders), click here.

Cob can be mixed in a variety of ways. Before industrialization, it was popular to mix a big batch in a pit by leading livestock through the cob, churning and mixing it with their hoofs. Now, professional cobbers often use tractors to turn out large amounts. For DIY projects (including building your own house), though, all you need is yourself. Oh, and a tarp is handy, too.

The most popular way of making cob these days is to mix the ingredients in small batches by stomping them (aka "dancing in them") on a tarp. Why a tarp? It's not strictly necessary, but it's a great help when trying to fully incorporate all of the materials.

Here's a quick run-down on how to mix cob:

First, mix your dry soil ingredients on the tarp. You can turn it by lifting one side of the tarp at a time, like the videos below show. Or, if you have two people you can each grab two corners, lift the tarp off the ground and rock back and forth, combining the dry ingredients with the rocking motion.

Second, add water and dance! Stomp on the cob until the water is incorporated. While stomping, stop every so often to turn the cob by lifting one side of the tarp at a time.

Third comes the straw. Sprinkle it on the wet mix in handfuls and stomp in a bit at a time. You may need to add more water. You'll know you have the right mix when it stays together in a rolled-up shape when you turn it. The technical term for this is "the burrito." You think I'm kidding?

Check out these videos to get an idea of the stomping and turning. For a good introduction to mixing and building with cob, read this partly-free-on-the-web book, The Cob Builder's Handbook.

Cob is sometimes referred to as "monolithic adobe." Like adobe, it is made from earth. Unlike adobe, though, cob walls are built without drying the earth into bricks first. Just plop some cob on the wall and press it in.

Ok, so it's not quite that simple, but almost. Be sure to build level all the way across the top of a wall. Press your fingers into the top of the wet cob when you are building, to give the next layer a rough surface to key into. Oh, and splooging? That happens when you press too hard on the top of the wall and the wet cob smooshes out on either side. This can be fixed, but don't let it get out of hand.

Here's a video that shows some mixing and some building with cob.

Youtube is a great resource to see what people are doing with cob all over the planet. Here's some videos proving just that.

This October I spent one very fun day cobbing on a garden wall. Here's the slideshow I made of the pics and video I took. It's kind of short, but there are some good clips of people cobbing and trimming.