PRESSED BRICK

One of the more modern additions to the earth building scene, dating from last century, the making of compressed earth bricks in manually or engine-operated presses is now a widespread practice around the world.

You make the bricks 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. You can produce the bricks on-site using a manual ram, or buy them from a manufacturer. Earth bricks are currently being produced commercially at Muriwai and Helensville in the Auckland region. 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, 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 things in earth building to concrete blocks in design and finish considerations.

You can sometimes use a sand/cement/earth mix for the mortar, although often a mix of hydrated lime, cement and sand performs better. Necessary tests are detailed in NZS 4298.