Adobe, common in the Southwest United States, has been used throughout history by indigenous people throughout the Americas. Adobe structures can also be found in North Africa, Spain, and the Middle East. Adobe is an excellent natural building material to use in warm climates, as it effectively keeps buildings cool, and is slow to release heat.
The composition of adobe can vary somewhat, but usually includes clay, water, sand and animal dung or straw as a binding agent. The mixture is poured into frame and air dried. Adobe bricks can be made in many different shapes and sizes, although some type of reinforcement might be added to larger bricks. Very large adobe bricks are called adobines.
When used for paths, walkways, or patios, adobe is often laid in sand, which allows for good drainage, extending the life of the bricks. The sand bed should be about two inches (5 cm) deep, and make sure that the sand is level so that the bricks do not break. Adobe bricks are usually irregular enough that they can't be laid in a tight fitting pattern. Spacing them with one inch (2.5 cm) open joints and filling the joints with soil can allow for plants and moss to grow through. Sand can also be used to fill in joints.
Adobe can also be used to construct walls, although care must be taken, as adobe bricks may weigh as much as 50 pounds (22.7 kg) each. Adobe walls need a strong foundation because of their weight, as well as reinforcement at the corners. The make mortar for this type of bricks, use two parts soil (the same soil as for the bricks), three parts sand, one part cement, and 1.25 gallons (4.7 liters) of stabilizer for each sack of cement.
Roofs can be made of adobe, especially in dry climates, and are usually flatter than other kinds of roofs. A wood or metal framework must be built to hold the heavy bricks, and cement can be added to the bricks for use in wetter climates. Adobe roofs are fireproof, and many houses made of adobe include chimneys made with the same type of bricks.
Although adobe walls and buildings used to decay in the elements, most adobe today is made with a stabilizer that keeps the bricks from dissolving. Stabilizers used for adobe include lime, cement, and bitumen. If the climate is very dry, such as in the Southwest United States, stabilizers are not generally needed.
Written by Bronwyn Harris