Adobe

From Wikinfo

Adobe is an earthen building material which is sometimes made into bricks. Adobe is a mixture of clay and sand. Too much sand and the material crumbles; too much clay and it will crack. To find the right combination experiment with the materials at hand until your bricks come out right. The same combining of sand and clay is used by Pueblo Indians to made the raw material for production of pottery or even to make molds for the casting of jewelry.

Bricks are made in an open frame, 10 inches by 14 inches is a reasonable size, but any convenient size is fine for your own use. After the mud is put into the frame the frame is removed. After a few hours the bricks are put on edge to finish drying. Bricks should be dried in the shade.

Use the same mixture you use to make bricks for mortar when laying the bricks and for plaster on the interior and exterior walls. It is sometimes useful to include occasional pieces of wood as you lay a wall to give something to nail insulation onto.

Bricks can be made waterproof by adding emulsified asphalt to the mud. To test bricks for waterproofing immerse them in water for 24 hours. A good brick will not soak up more than about a 1/16th of an inch of water. To test for strength, drop a finished brick from a height of 3 to 5 feet to see if it breaks. Sometimes if the sand is too fine, the finished bricks will be weak. Straw is sometimes, even traditionally, added to the mix when making adobe bricks, but offers no particular advantage.

Because an adobe wall, either with bricks or using a rammed earth technique, is massive it will hold heat or cold. That means insulation needs to be put on the outside of your wall so once your wall is warmed up it will maintain the stablity of the temperature of the building. A south facing adobe wall may be left uninsulated in order that it can collect heat during the day. It should be thick enough that it remains cool on the inside during the heat of the day but should be thin enough that the heat can be transfered through the wall by evening. Such a wall can be covered with glass to increase heat collection. Used in a passive solar home such a wall is called a Trombe wall.