Cob is a wonderful material, usually made from clay subsoil, or sometimes with added clay slip if needed. It has been used for around 6,000 years as a building material, and it is estimated about one-third of the world’s population live in mud houses.
There are really good reasons for this. It is cheap, can be made with relatively little experience, is can be made to suit your own environmental conditions, and it is also beautiful. Oh – and I forgot – it also absorbs the heat of the sun, called passive solar gain, which makes it let the warmth out at night.
So perfect for a cob greenhouse.
I have just finished teaching a course making the second section of our second cob greenhouse. People learned the mix, made it by foot, and built it by hand. And had lots of fun sculpting it too!