Compressed earth bricks made in manual or engine operated presses are one of the more modern additions to the earth building scene, dating from last century. This technique is now a widespread practice around the world.
The bricks are made from a dry mix, often stabilised with up to 10% cement. The compression given by the machine compacts the soil particles together to make dense regular shaped bricks, usually around 300 x 300 x 130mm in size. Most presses will enable some variety of shapes to be made so holes for reinforcing and rebates for window jambs can be pre-formed, but bricks of a different size are usually difficult to produce.
Bricks can be produced on-site using a manual ram, or can be bought from a manufacturer. Of course earth bricks with a high cement content trucked to your site don’t score so well on the energy conservation scale.
Being hard, dense and regular, pressed earth bricks can be laid up very precisely to form geometric shapes, or laid more loosely depending on the aesthetic results required. These bricks are the nearest thing in earth building to concrete blocks in design and finish considerations.
Sometimes a sand/cement/earth mix is used for the mortar, although often a mix of hydrated lime, cement and sand performs better. Necessary tests are detailed in NZS 4298.