- AN EARTH BRICK
A brick comprising of granular components held together by clay
- A SEMI-STABILISED EARTH BRICK
An Earth Brick in which the colloidal attraction is enhanced,
strengthened or otherwise improved by admixture(s).
- A STABILISED EARTH BRICK
An Earth Brick in which additives prevent the ingress of water to clay
- An ADOBE OR PUDDLED BRICK
An Earth Brick produced by adding water to the soil until sufficiently
plastic to mould into a brick by hand or sufficiently liquid to flow
into a mould.
These may also be semi-stabilised or stabilised.
- A PRESSED EARTH BRICK
An Earth Brick moulded by applying mechanical or hydraulic pressure to
soil with an optimum amount of water for maximum compaction.
may also be semi-stabilised or stabilised.
|NOTE: If a brick is held together by other than colloid attraction, a
number of factors may change, showing that functionally it is not an
- The thermal resistance of the brick may decrease
- The brick would not be plastic under stress
- The porosity of the brick may increase
ACCEPTABLE PERFORMANCE OF EARTH BRICKS:
- Bricks should endure normal temperate rain on a
vertical surface without physical protection or surface treatment.
- All bricks should have a modulus of rupture (M.O.R.)
least 150 Kpa, regardless of their intended use as loadbearing or
- Mechanical and chemical analysis is not sufficient to
determine a suitable soil for earth wall construction. Test bricks must
be made using intended production procedures, and tested for
strength and durability.
- Soils should be composed of a good grading of 20 mm.
stone, gravel, sand and silt with enough clay to coat all particles and
fill the remaining voids with a slight excess.
TESTING OF BRICKS:
- DURABILITY OF BRICKS
Bricks should be tested for durability by a drip or trickle test, which
can be replicated in the field and demonstrate:
- erosion by the size and depth of pitting
- structural weakening and potential
erosion by depth of softening
- porosity by width and depth of
- growth or expansion by measurable welt or
- growth or expansion by cracking after
- STRENGTH OF BRICKS
Bricks should be tested for strength by a modulus of rupture test that
can be easily replicated in the field.
NOTE: See Testing Procedures.
SIZE OF BRICKS:
- Dry bricks should not weigh more than 15 kilograms.
- Bricks should have one dimension to achieve at least
a 250 mm. single skin wall.
LAYING OF BRICKS:
NOTE: Mortar joints should be of similar material to the bricks to
achieve sufficient bonding to produce a homogeneous wall with uniform
- MORTAR BEDS
- Mortar beds should be the minimum
accommodate the irregularities of the bricks plus the maximum aggregate
size in the mud mortar.
- Mortar beds should be the full width beds
and finished as struck or flush.
- MUD MORTAR
- Mud mortar should be of similar material to the
bricks screened to 12 mm. minus.
- Screening may raise the effective clay
- Sand may be added to clayey soils to reduce
cracking and shrinkage.
LOAD BEARING WALLS
NOTE: A 250 mm. minimum wall thickness is recommended not for
structural considerations alone. It also gives the minimum "thermal
lag" necessary for external walls and sufficient thermal mass for
internal walls for most climates.
- 250mm. should be the minimum wall thickness.
- Wall thickness, roof fixing and positioning of
intercepting and buttress walls should be adequate to withstand
reasonable wind design loads.
- Unstabilised Earth Bricks should not be used below
the following points:
- 150 mm. above the external finished grade.
- 75 mm. above any floor on ground.
- A windmoulding strip should be fixed to all window
frames, door frames and posts adjoining the walls.
- At least one 230 mm. gal. frame tie, every 3 courses,
should be attached to all adjoining frames and posts.
- Expansion joints are not necessary for earth walls.
- An earth wall does not need a cavity as it is not
and a solid 250 mm. wall has a sufficient "thermal lag" or "effective R
value" for most climates.
- It is recommended to use 250x100x3mm Duragal wearing plates on the earth walls beneath rafters or roof beams.
- Use mortar mix to mud over chases and reveals for a uniform surface.
BRICK TESTING PROCEDURES
- (a) DRIP TEST: The brick is placed with the
30 degrees from horizontal and 100 ml. of water is dripped from 400 mm.
above the middle of the brick face. After 30 minutes the following
measurements are taken:
- The depth of the pit where the drips struck the
- The depth of softening measured by pushing a 75 x ?
mm. nail into the brick by hand, 50 mm. below the pit.
- The height of any welt or swelling of the wet area
the original dry surface of the brick. This is best measured just above
- The depth and width of infiltration of water after
breaking the brick across the middle.
- The extent of any cracking after drying.
- The maximums for a durable brick should be:
- depth of pit 5 mm.
- depth ot softening 5 mm.
- Height of welt 0.5 mm.
- Depth of infiltration 20 mm.
- NOTE: the brick is porous if water does not reach
lower edge of the brick.
- SWINBURNE EROSION TEST
- MODULUS OF RUPTURE TEST
- The minimum M.O.R. should be 150 Kpa
- CSIRO ACCELERATED EROSION TEST