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.
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