CHAPTER FOUR
Earth As A building
material
Why looking for Alternative building
materials?
Production of building components using
the CONVENTIONAL TECHNIQUES is
highly capital and energy intensive.
In the case of low cost housing, building materials
account for 70-75 % of the total cost of
construction.
For example: Average cost break-up for low cost
building construction.
Material percentage
Cement 18%
Iron and steel 10%
Brick 17%
Timber 13%
Sand 7%
Aggregate 8%
Sum 73%
The remaining 27 % goes to labor.
Now a days the cost of conventional building
materials such as steel, cement, bricks, timber
and other inputs as well as cost of timber is
increasing dramatically.
Therefore, there is a need to adopt eco-friendly
and sustainable building materials and alternative
construction methods either:
by up - gradation of traditional technologies using
local resources or applying modern construction
materials and techniques with efficient inputs
leading to economic solutions.
EARTH AS A CONSTRUCTION MATERIAL
HISTORICAL BACKGROUND
From the roof of the World in Tibet or in the Andes
Mountains in Peru, to the shores of the Nile in Egypt
or in the fertile valleys of China, many are
examples of earth used as a building material.
Features of earth as a building material:
Earth as a building material has the following significant
features:
Strength: it can get by adding d/t stabilizer materials
Cost and Energy efficiency
Virtually Sound proof; Due to dense properties
Non Toxic
Environmentally friendly
Durable; Due to fire and pest resistance. E.g. fasilgimb
Available and abundant raw material
Aesthetically pleasing
Thermal Properties
1. STRENGTH
Earth buildings are structurally sound.
The strength, durability and longevity/age/ of
Earth Blocks stand in contrast to other building
materials.
A typical wood frame building has an average life
span of 75 years while earthen structures will stand
for centuries .
COST AND ENERGY
Probably the most impressive and important selling point of
earth building is the incredible energy savings the owner will
be awarded throughout the life of the building.
Energy efficiency can also be realized in the construction
process itself.
Earth blocks are made on-site saving in transportation costs
and fuel consumption and require little energy in the block
making process.
3. VIRTUALLY SOUND PROOF
Earth is so dense building material that occupants
are relatively protected from the outside World.
Sound recording studios have been built with
pressed block for that very quality.
Earth block buildings create their own world on the
inside, which most people find is an added bonus.
4. NON-TOXIC
Earth Block making itself is a non-toxic process;
therefore, buildings themselves are clean.
Earth block is a frequently chosen material for home
construction for those people suffering from chemical
sensitivity .
It’s a win-win for both occupant and the community
when new buildings are constructed with earth-
friendly materials.
5. Durable
When we consider that the oldest structures
standing throughout the world today are
made of earth, the statement that earth
construction is durable speaks for itself.
The world largest adobe mosque found in Mali
Main techniques using earth as a
building material
In fact 12 main methods of using earth as a
construction material are recognized.
Among these, seven are very commonly used and
represent the main classes of technique.
Adobe
Blocks
1. Adobe:
The earth, in a malleable state, often improved by
addition of straw/grass/ or other fibers, is molded
in to a brick form and dried in the sun.
2. Rammed earth:
The earth is massively dumped into formworks,
compacted by means of a rammer, layer by layer,
and formwork.
Rammers
Manual rammers consist of a wooden or steel rod
with a heavy wooden or metal striking head.
The heavier it is, the better the compaction, but the
more tiring for the user.
3. Straw clay/clay-stwar:
In this technique the soil used is very clayey and
spread out in water until a homogenous thick liquid
state is attained. This muddy liquid is mixed with
straw in order to form a film on every wisp.
It is put in to place by means of a formwork in order
to erect a monolithic wall, which necessitates a
primary support structure.
4. Shaped earth/Direct shaping:
The earth often improved by the addition of straw or
other fibers is shaped in to a wall using the same
technique as that used for pottery, directly without
using any kind of mould or formwork.
Only the hands of the builder are required.
This ancient technique is still widely used.
5. Extruded earth:
The earth is extruded by a powerful machine similar
to, or derived from, the machines used for the
manufacture of fired brick.
6. Cob
Basically the cob procedure consists of stacking earth
balls on top of one another and lightly tamping them
with the hands or foot, to form monolithic walls. The
earth is reinforced by the addition of fibers, usually
straw from various types of cereal or other types of
vegetable fiber, such as grass and twigs.
7. Compressed earth blocks
A compressed earth block (CEB) or stabilized compressed soil
block (SCSB) is produced using a machine that either
manually or mechanically compresses the soil into a mould.
Nowadays, a wide variety of presses is used. Products range
from accurately shaped solid, cellular and hollow bricks to
flooring and paving elements.
Nowadays it is the technique of rammed earth,
compressed block and adobe, which are the most
widespread and have reached extremely high
scientific and technological levels.
A wide range of applications
The construction techniques mentioned above are
highly flexible and permit the construction of a
wide variety of components and construction
systems.
Foundations ,base course, walls and pillars,
openings, floors and pavements, flat and pitched
roofs and
Arches and domes, tiles, insulating elements, stairs,
flues and chimneys, built in furniture and others.
