Photo shows a 200 year old clay and riverstone wall in Placerville, Placer County CA. The structure was made with straight clay mortar and local stones fom the river. This building is near Sacramento, California. There is no insulation in the walls, and the stones were bedded right into a layer of local clay acting as the mortar, and is still standing despite earth tremors and quakes over the decades. The new door was placed in the last 30 years, and stones were pulled from the wall, and bricks and cement mortar were added. The building is now a trendy art gallery and coffee shop. The clay mortar can be scratched easily with a fingernail, but surprizingly has not eroded or crumbled from just exposure to weather. It gets to over 100 degrees in summer, and heavy rains, some snow, and cold weather in winter have not ruined this hand built structure. Clay and Bool- as it is known in Scotland is stones bedded in a clay mortar, and you can see how strong it can be. Modern earthquake requirements will not permit building this way in seismic zones. Good books and DVDs about clay building: Building with Cob-A Step-by-Step Guide-book DVD-Natural Building and a New Sense of the Earth The Hand-Sculpted House-book Adobe And Rammed Earth Building: Design and Construction Build Your Own Earth Oven by Kiko Denzer Stone House: A Guide to Self-Building with Slipforms-book