Folder Materials - Natural / Rural
"Natural building" is increasingly used worldwide to connote the simple and ultra low carbon systems that human beings have used for thousands of years - and are now reviving, usually with a few modern touches. Since you generally can't find much clay or straw or unmilled timber in cities, we also call it "rural".
Earthen buildings, in their many forms around the world, can be thought of as clay-based concrete, as opposed to cement-based concrete. Many are, yes, mere mud huts, but many are magnificent architectural gems, and very effective as shelter.
And they are cheap, so that's what the poorest of the poor throughout history have had to use - thus the strong association of earthen building with squalor. But some of the most effective and lovely new structures anywhere are made with earth, signals of a worldwide renaissance of earthen architecture.