Raw earth
Mud (adobe & cob)
Subsoil with the right clay content, shaped wet as cob or dried into adobe blocks. The oldest building material there is: most humans who ever lived slept inside earth walls.
How it behaves
High thermal mass with a little insulation from its straw: a thick mud wall delays the day's heat by hours and evens out extremes. It breathes moisture freely, but needs a roof overhang and a plinth to keep rain off.
Where it belongs
Kutch and Rajasthan · The Sahel · Middle East · The Americas
In a modern project
Compressed stabilised earth blocks (CSEB) bring earth into code-compliant urban work; interior mud plasters buffer humidity in sealed apartments.