An Earth House is built almost entirely of natural products, such as sand, clay and straw, and recycled products, such as bottles and aluminium cans. Methods of building Earth Houses include 'Straw Bale', 'Cob' and 'Rammed Earth'. All of these are old methods of building which have had something of a revival in recent years. They make beautiful homes, and their physical properties mean they require very little energy to run.

Straw Bale

The walls of Straw Bale homes are constructed from baled straw (from oats, wheat, rye, barley, and rice). The bales are stacked like blocks to form the walls which are then covered in plaster, which can be either a mud plaster taken from the site, or a cement plaster from a supplier. This type of wall is very insulating and provides good soundproofing. Straw Bales are inexpensive and buildings can be assembled using unskilled labour.

Straw is the stalk left in the field after the seeds have been harvested, and is no longer alive. It is not the same as Hay, which is living grass and not suitable for building these homes. However, it is completely sustainable.

Rammed Earth

Sand, clay, silt and gravel are mixed with 5 - 10% cement. A small amount of water is added and this concoction thoroughly mixed, making a semi-dry concrete. The mixture is them dumped into forms varying between 1 and 2 feet in thickness, and rammed either by hand or power tamper. When the full height of the wall is reached, the form is removed and set up adjacent to the first wall where the entire process is repeated. The two walls are then bonded together using a continuous reinforced concrete beam.

Cob

The word 'cob' comes from old English and means a lump or rounded mass. This method of building uses hands and feet to form lumps of earth, mixed with sand/small stones, straw and water - the soil dictates the exact composition. The mixture dries to a hardness comparable with concrete. The walls are so strong that a wall 8 inches or greater in width is fully load-bearing. This method of building is very easy to learn. Unlike other methods, there are no forms, ramming or cement - therefore this method lends itself to organic shapes such as curves, arches and niches.