An adobe is a unit which may be formed by hand or in a frame, but which is not compacted. Adobes are made of similar size to each other to allow them to be laid together in a mortar to form a wall.
The term adobe; is also likely to be taken from the Arabic for brick, al taub (اللبن), where it has been corrupted into the Spanish adobe.
The soil used for adobe construction tends to be richer in clay and silt than the soil mixtures used for rammed earth or cob construction. These soil types may be more susceptible to shrinkage, and so additives such as straw or grass are often included to prevent cracking.
Hand-formed units are made by roughly shaping the wet soil to the required dimensions. This method allows any shape to be formed (for example into spheres or cuboids). More common is the use of a standardised mould; to increase productivity, moulds can be made to produce more than one brick at a time.
To make blocks, wet soil is placed into the mould and allowed to dry slightly; then the mould is removed and the unit is allowed to dry in the air. To assist drying, the bricks are usually rotated onto their header face after a time, to allow a larger surface area to be exposed. The bricks are usually left to dry for a period of weeks before being laid to form a structure.
Adobe walls are constructed in the same manner as fired masonry, with similar bond patterns and mortar bed joints. The mortar should be composed of a similar material to that of the brick. To lay bricks, each brick is first dipped or coated in water, and then laid into the mortar bed. Adobe can be formed into arches, and barrel vaults and domes are popular in many parts of the world. Decorative patterns may be formed in adobe walls by using a different bond pattern, by laying the adobes on end, or by manufacturing insets or protrusions from the wall.Many adobe walls are rendered after construction. This both protects the face and allows a clean face to be presented, reducing the chance of water penetration into the mortar joints.