A cob wall (see Figure 14-3) is made of chunks of mud slapped into place on top of one another and then smooshed into whatever size and shape you want the wall to be. This technique makes for a lot of artistic freedom, so cob walls tend to be curvaceous, interesting, and often embellished with bas-relief dragons and lizards, embedded bottles, and other handmade artsy touches.
The first step in making cob is to mix the earth, straw, and water. One traditional approach is to place the materials into a pit and then stomp on them. Often this is done by several people who link arms, chant, and make a dance out of it. All very festive. You also can mix on a tarp, concrete slab, or sheet of plywood. To mix, add water to the soil, working it until it's a doughy mass and not too wet. Then start adding straw (a total of about 2 pounds of straw per cubic foot of soil) and stomping it in. When the mix is stiff, and it's difficult to pull a chunk away from the larger mass, it's ready to use.
Now you can knead "loaves" of the wet soil and plop them on top of one another to form the wall. Make the loaves small enough that you can carry them to and from the mixing location to the wall. To get a good bond between layers of cob, use a cobber's thumb to punch the newly-applied loaf into the ones below it, stitching the layers together into one single mass of soil. (A cobber's thumb is a stubby wooden rod with a ball at the end that's just big enough to fit in the palm of your hand. In a pinch, a broom handle or wooden dowel will do.)
As you go, eliminate any seams, gaps, or voids, which can weaken the structure. Place yourself above the work to avoid muscle strain and to use the weight of your body to compress the cobs into a single mass. Don't work the wall too much, though, because excessive pressure can make it turn to jelly and lose strength. Allow the finished surface of the wall to be somewhat rough so it dries properly; a smooth surface will seal moisture inside. (Your earthen plaster coat will cover the roughness.) Don't let the surface dry out as you're working; otherwise you'll weaken the bonds between the layers of cob. If the surface does dry out, be sure to rewet it before adding any more cobs. If the wall starts to bulge out from the weight of the material, trim off the excess and slow the process down to allow the soil to partially solidify.
It's truly amazing how much weight you can move around safely if you know what you're doing. A guy in Michigan can move and raise stone blocks of almost 10 tons by himself — without any heavy equipment. He's replicating
Stonehenge in his backyard. Search YouTube (www.youtube.com) for Wally Wallingtonto see an amazing sight. But you're not Wally, and you'd better learn what you're doing before you start heaving rocks around.
Was this article helpful?
How would you like to save a ton of money and increase the value of your home by as much as thirty percent! If your homes landscape is designed properly it will be a source of enjoyment for your entire family, it will enhance your community and add to the resale value of your property. Landscape design involves much more than placing trees, shrubs and other plants on the property. It is an art which deals with conscious arrangement or organization of outdoor space for human satisfaction and enjoyment.