Cob is a mixture of clayey soil, straw and water. These 3, simple ingredients are mixed together to create a medium that has been identified globally as an effective and efficient building material.
Clayey soil must contain aggregates, such as gravels and sands
Barley straw is commonly used as a binder when making cob
Here at Earth Blocks Ltd we use rainwater from diverted downpipes
So, we now have our raw materials to make cob. An important first step is to ensure that the surface [for mixing] is thoroughly wetted down. Straw is then teased on to the mixing area. In this example we’re using half a bale of straw.
We have used half a bale of straw for the base layer
Soil is placed on top of the straw base-layer
A final layer of straw is teased on to the soil
We now have all of the ingredients layered and ready to be combined together. Mixing cob by compaction (rather than rotation) is by far the best method.
Using a tracked machine like this one, delivers a wider compaction footprint when driving over the materials. This process is repeated several times
After 2 or 3 passes, the cob is piled up and spread out again. Tracking and piling are repeated 5 or 6 times
