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Introduction
The essay has been organized to explore the availability of earth as a construction material; firstly, it
focuses on the history and background of its usage. Then, a few examples of vernacular and
contemporary buildings are presented. These examples are followed with a myriad of suggestions
and proposals to make various earthen mixtures more compatible to different climates and
structural demands, with the preference city of Sheffield as a sample.
1-History and Background
One half of the population of world about three billion people reside in earth and similar materials
like clay or mud constructed buildings. They can be found on all continents with different climatic
conditions in various shapes and sizes from individual shelters to massive ceremonial or religious
buildings. More specifically in almost all hot-dry moderate climates of the world, has been the main
construction material. It has not been possible to fulfill the demand of shelter in developing
countries with industrial materials, like brick, concrete or steel nor with the capacity of industrialized
production or even to satisfy this need with the financial resources. Shelter requirements in
developing countries can only be fulfilled by the local building material usage and through self help
construction techniques.
2- Earth
Earth is one of the simplest materials used for construction, and all earth buildings have the same
basic components: soil from ground, and water.
2-1-What one should know about earth as a building material:
Earth as a building material has usually owned different names. “Scientifically referred to as loam, it
is a mixture of clay, silt (very fine sand), sand, and sometimes larger aggregates like gravel or
stones.” Mud bricks or adobes are usually used at the time of speaking of handmade unburnt bricks,
when speaking of unburnt bricks the term soil blocks is used and if it is compacted within framework
it is named rammed earth.
In another word, the techniques of preparing the earth are split into two classes: those in which
individual units are made, dried then transported to the building site to form the structure which are
called adobe and compressed earth blocks, and those which are produced in situ and are
homogeneous monolithic constructions named cob and rammed earth.
2-2- Qualifications
In many forms of construction from earth, other materials are included in the mixture called
stabilizers. They combined with soil to improve its structural characteristics for instance tensile
capacity and shrinkage which leads to cracks and improvement in shear strength. The former can be
gained by adding hair, straw and the latter by cement.
Accordingly loam has three disadvantages:
1- Loam is not a standardized construction material:
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Different types and amounts of clay, silt, sand and aggregates could be found depending
on the site where the loam is dug out. As a result, with alteration in locations of
excavation site and the procedure of mixing for a specific application, the characteristic
of loam may differ.
2- Loam mixtures shrink when drying out
Because of the evaporation of water used for preparation the mixture (which is
necessary for binding) shrinkage cracks will occur. The shrinkage can be managed by
changing the amount of clay and water.
3- Loam is not water resistant
Loam has to be sheltered from rain or frost; this matter can be done by roof overhangs,
damp roof courses and appropriate coatings on surface and alike.
It is prominent to mention the advantages of loam in comparison to industrialized building materials.
1- Loam balances the air humidity: loam is able to absorb and desorb the humidity faster than
other materials and as a result it improves the indoor climate.
2- Loam stores heat
In thermal insulation massing is always helpful, since loam is a heavy material it stores heat.
In climatic zones where the diurnal temperature differences are high like central zone of Iran
-which will be introduced later in this paper- or where it is essential to store solar heat gain
by passive means, loam can be effective on indoor climate.
3- Loam saves energy and reduces environmental pollution
As the construction of loam is an in situ procedure and it is gained at the time of excavation
for foundation; to prepare and transport only about 1% of the energy needed for
production, transport and handling of burnt bricks or reinforced concrete is used. Thus, loam
is significantly a more environment friendly material.
4- Loam is always reusable
Unburnt loam can be recycled any number of times. After absorbing water the dried loam
turns to wet clay again and can be reused, so it can never be a harmful material for
environment.
5- Loam is ideal for self-help construction
Earth construction techniques can usually be performed by nonprofessionals with just one
experienced supervisor. The techniques are labor intensive and the tools are very cheap.
6- Loam preserves timber and other organic materials
Owing to its low equilibrium moisture content, loam conserves timber elements that are in
contact with it, as it keeps the wood dry. The importance of this characteristic is that it
blocks the growth of insects and fungus, because they need at least 14% to 20% humidity.
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3-Vernacular use:
To be more familiar with this material
analyzing a number of examples would
be helpful:
Firstly the biggest mud brick building in
the world:
3-1- The great mosque of Djenné: the
walls depending on their heights are 41-
61 cm thick and are made of sun baked
mud bricks coated with a mud plaster,
which makes the surfaces smooth and
adds a sculpted look to the whole
building. According to one of the
advantages of loam which is discussed
earlier the thickness of walls keep the
building cool during the day and release
it after a few hours, which keeps the
interior quite warm. The façade of the
mosque has the same material as a
traditional house in Djenné. To preserve
the building the local climate which has
a severe changes in temperature and
humidity, palm branches have been built
into structure to condense cracks and
provide ready-made scaffolding for
future repairs. In addition ceramic pipes
stick out from the structure, to guide the
water draining from roof to the walls.
3-2-Another instance are the central
cities in Iran, life in the deserts town in
centre of Iran are accompanied with
scorching sun and threat of regular
sandstorms. In order to overcome these
difficulties these conurbations are
formed in a unique vernacular style and
have an ingenious underground water
supply system, known as qanats.
Image01- Molds for adobes
Source: Earth : construction handbook (the building material
earth in modern architecture
4
Residential buildings are constructed from adobe, with thick walls made of muddy bricks, which is
the only available material. These buildings rise up to 6 meters (20ft) tall, with domes and arched
roofs. Surprisingly the domes have positive effects on the indoor climate working as an insulation
parameter of the space. The latter is derived from the fact that usually these domes are constructed
in two layers so the air between these will act as insulation, needless to say that these characteristics
are more beneficial with the adobe material and its heat storing possession.
Since the material for construction is coming from the excavation, the house ground floor is a little
below the street level, with the first floor living quarters 3-4 meters (10-12ft) above it.
As it is discussed earlier the adobe walls store the heat from sun and release it at night, in winters it
is quite favorable but in summers it would cause unbearable heat, which led to invention of systems
using wind catchers that are linked to a duct and water reservoir (a branch of those qanats) to cool
the place.
Image 02- mosque wall and dome
Source: Handmade houses and other buildings: The world of vernacular architecture
Image 03- a typical house in Yazd
Handmade houses and other buildings: The world of
vernacular architecture
Image 04- a windcatcher in Yazd
Handmade houses and other buildings: The world of
vernacular architecture
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The foremost example of this desert architecture is the city of Yazd, which is not only one of the
largest cities in the world which is made of adobe, but also has the most complex qanats complex
which is still being used. Despite its beautiful adobe houses this city owns the tallest wind catcher
and a few numbers of double sided ones.
3-3- Yemen tower house:
Tower houses are a dominant form unique to southern
Arabia; they are originally from pre Islamic times in Yemen
where the tribal quarrels was the motivation of creating an
impressive defending towers out of local material. They have
spread across the country and have become a very popular
form of housing for big families due to their capability of
extension in the height; i.e., adding more storeys to the
tower. They are usually five storeys high and some reach as
many as eight or nine.
The foundation of the towers is made of stone or earth (sun-
dried clay, mud bricks or fired blocks), in cities the two first
floors are made of tufa and the upper levels are from mud
bricks.
4-Contemporary examples:
Modern houses which are constructed out of loam need not to have any characteristic outward
appearance. They can be modern or traditional, complex or
simple, exclusive or humble. In cold climatic regions loam is
not usually visible from outside, they are coated with specific
thermal insulation and weather protection material.
Nonetheless, the interior can manifest any kind of earth
building techniques and applications.
4-1- Residence, Hörnerkirchen, Germany
Due to the poor soil conditions; the floors are made of
concrete slabs on which a lightweight loam layer was applied
in order to give sufficient thermal insulation. The walls are
constructed of wooden skeleton with infill of lightweight
mineral loams and additional insulation layers on the outside;
moreover, the wooden boards with air cavity are forming the
façade.
Image 05- a tower house in Yemen
Handmade houses and other buildings:
The world of vernacular architecture
Image 06-Residence, Hörnerkirchen, Germany
Source: Earth: construction handbook (the
building material earth in modern
architecture
6
4-2-Two semi-detached houses, Kassel, Germany
All interior walls expose the timber frame and
display the loam surfaces; meanwhile unburned
loam is the dominant material for shelves and even
bathroom sink.
4-3-Low-cost housing project, Mount Abu, Rajasthan, India
This residence is a prototype for low cost housing project
for staff and students in university. It is covered by two
crossing vaults built of unstabilised soil blocks produced in
a manually operated block press from the local soil and
also they were constructed with the Nubian technology.
4-4- Farmhouse at Wazirpur, India
The single-storied house with the structural frame
consists of load bearing stone columns, which
support beams and stone slabs to form slightly
domical enclosure over all rooms, and the only
part which is from adobe is the infill walls and the
rest of the house is made of various materials like
stone for shading or steel for security grills.
Image 07- Two semi-detached houses, Kassel,
Germany
Source: Earth: construction handbook (the building
material earth in modern architecture
Image 08- Low-cost housing project, Mount Abu, Rajasthan,
India
Source: Earth: construction handbook (the building material
earth in modern architecture
Image09- Farmhouse at Wazirpur, India
Source: Earth: construction handbook (the building material
earth in modern architecture
7
4-5-Nubian vault building: the presented image is a cross-section of a building made of earth, the
wall on the right side illustrates the underlying
construction of mud or brick; on the left the wall is
coated with a render made of mud or cement. The
roof is waterproofed by plastic sheets covering the
surface and the final render of enriched mud mortar
on top.
5-Appropriateness
One question that needs to be asked, however, is whether this material suitable for any kind of
climatic conditions? Until this part of the paper and passing through the examples it is depicted that
earthen buildings were and still are the most inhibited spaces. Moreover they were the first building
material all over the world with some additives to overcome weather severity.
In the instance of tower houses in Yemen it is derived that the buildings can bear the nine storey
height only with mud bricks. On the other hand; the examples of contemporary mud houses made it
clear that in order to have a strong structure the mud bricks can be used with timber or stone
columns.
5-1- Region
For analysing the appropriateness of the material for cold and humid climate the selected region is
in Northern England like Sheffield. By researches in the climatic conditions in Sheffield it is derived
that approximately 170 days of year it rains and the percentage of humidity is about 60% in average.
In order to design a building with earth or more specifically with adobe there are a number of
considerations like water proofing the façade, or damp resistant foundation.
In presented examples from earlier times and contemporary, it is depicted that surface coatings and
pipes for rain drainage are essential parts of design.
6-Suggestions
Respecting the following facts can improve the designed buildings:
1-Trench for foundation: minimum depth of 0.8 meters and minimum width equal to the wall
thickness but not less than 0.4 meters. The trench can be filled with stones infield and layers of
cement grout to form strip foundations underneath walls. If the pedestal course is constructed of
concrete, a formwork can be rose for the pedestal course, and can be made alongside with the
foundations. The vertical wall reinforcement must be erected in place and be set in the base. The
Image10- Nubian vault building
Source: Handmade houses and other buildings: The
world of vernacular architecture
8
canes must be linked with nylon threads or similar ways to the formwork to guarantee right
position which is illustrated in image below.
2-Plinth/Pedestal course: the first few courses of wall on foundation should be built out of mud brick
or stone. The height of pedestal should be above the flood water line or 350mm above the ground
level in minimum. Vertical cane reinforcement will guarantee the connection with the foundation;
furthermore, the plinth course can be made of concrete and after completion of plinth masonry a
multiple layered of damp roof should be installed.
3-Different bonds for adobe walls are possible for the wall construction with masonry materials. In
the two below images English and Flemish bonds with 1 brick/block thickness for wall is
recommended. To build a more technical construction horizontal reinforcement should be installed
every fourth layers of adobe.
Image 11- Foundation construction (Dowling,2002)
Source:http://www.staff.city.ac.uk/earthquakes/Masonr
yAdobe/ImprovedAdobe.html
Field stone- max size 250mm
Grout- cement based mixed in proportion 1:4 (cement: sand) by volume
Vertical reinforcement- bamboo or canes sticks with diameter around 20mm. The length should be determined as follows: H=400 + wall height +bond beam depth(but min 200) ,[mm]
Image 12- Flemish bond for one brick thick wall
Source:http://www.staff.city.ac.uk/earthquakes/M
asonryAdobe/ImprovedAdobe.html
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4-Adobe bricks/blocks
Adobe bricks are made of clayey earth including 30-40% clay and 60-70% earth which are mixed
together with water. To strengthen the tensile capacity straw can be added to the mentioned
mixture and the proportion would be 7-10 kg per m³ of dry earth. Then the mud mixture should rest
for couple of days for the optimum water penetration through the mixture to activate the binding
characteristics of the clay, noticeably it should be done before the making of the mortar or the brick
itself.
5-Mortar
The properties of mortar are very prominent because of its direct contact with the blocks which
already absorb moisture and also will limit the dying shrinkage. The joint mud (mortar) should be
from the same or similar mixture which is used for making the blocks. Some coarse sand can be
added to the mixture to make it smoother and also sand will fill the cavities between the earth
particles which leads to a more integrated mixture.
6-Roof construction
Ideally the roof should be light that the adobe walls can bear its load; in addition, it would reduce
the risk of casualties in the events of roof collapse or earthquakes. Earthquake resistant roof type is
the low-pitch pyramidal roof, with four planes, sitting on a horizontal beam on top of adobe walls.
Single slopped timber roofs are also recommended, but it should be considered that “in all types of
roofs the structure should not transfer the thrust to the walls.” Moreover, timber plate or timber
wedges are recommended to uniform load distribution onto bond beam. To avoid water leaks,
different approaches can be considered basically it depends on the climatic conditions, but generally
500mm of overhang is preferred in all of forms. Accordingly, the material for roof covers a wide
range like board wood sheathing or plywood, ridged sheets, engineered wood, plastic coats and so
forth. Needless to say that clay tiles are not proper for this form because of their high mass.
Image 13- English bond for one brick thick wall
Source:http://www.staff.city.ac.uk/earthquakes/Mas
onryAdobe/ImprovedAdobe.html
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7-Plastering
For protection of adobe walls plastering is essential, preferably hydraulic lime or mud-lime based
plasters are suggested; also, they can be improved by adding straw as reinforcement. One of the
facts that should not be neglected is not using cement in the plaster mixture, because the adobe
wall needs to breathe.
7-Consideration
In following some initial points are mentioned which worth considering at the time of design:
Build one storey houses Provide foundations Provide buttresses at all corners and junctions of walls Roughly squared rooms Provide at least 4 courses of plinth masonry above foundations Build light low pitched couple roof, four sloped roof or single sloped roof The roof should transfer only vertical loads to the walls. Include a collar beam when
constructing pitched roofs. The height of wall should not be greater than 8 times its thickness. The length of a wall, between two consecutive walls at right angles to it, should not be
greater than 10 times the wall thickness’t’ nor greater than 64t2/h where h is the height of wall. When a longer wall is required, it should be strengthened by an intermediate vertical buttress.
The width of an opening should not be greater than 1.20 m. The distance between an outside corner and the opening should not be less than 1.20 m. The sum of the widths of openings in a wall should not exceed 1/3 of the total wall length. The bearing length (embedment) of lintels on each side of an opening should not be less
than 0.5 m. An adequate configuration is shown on the Figure below.
Image14- construction proposal
Source:http://www.staff.city.ac.uk/earthquakes/Mas
onryAdobe/ImprovedAdobe.html
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8- Supportive material
According to the earlier discussion, earth is the first material that human has used for construction in every climate and geographical situation, it is proven that this material is applicable everywhere.
More significantly for a climate like Sheffield and with respect to the fact that it is situated in peak district, the initial adobe constructions can be supported with the abundant stone and wood available from Peak District. Researches on contemporary adobe architecture in Germany which is presented earlier had shown that having stone columns and timber particles as a part of structural design would be a technical support for the whole construction.
Needless to say that having pitched roofs which are water proofed with special coatings or even engineered clayey claddings are some of the main design points.
9- Conclusion:
The present study was designed to study on one of the low impact materials in architecture production and its history, vernacular use and contemporary samples. Adobe which is made of earth, water and some additives like straw was the focused point.
Returning to question posed at the beginning of this study, it is now possible to state that adobe is a good material for construction in different parts of the world, however to overcome some of the bad effects of climatic conditions like humidity a few number of notes should be considered. It is also recommended to consider some supportive elements both in structure design and clay mixture; moreover, examples are provided to make the context wider for future research.
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Bibliography:
Jaquin, P, Augarde, G, 2012, Earth building: history, science and conservation, HIS BRE press
May, J, 2010, Handmade houses and other buildings: The world of vernacular architecture - Thames
& Hudson
Minke, G, 2000, Earth : construction handbook (the building material earth in modern architecture,
WIT press
Mumovic, D and Santamouris M, 2008, A hand book of sustainable building design & engineering: an
integrated approach to energy, health and operational performance, London ; Sterling, VA :
Earthscan
Williams- Ellis, C, 1999, Building in cob, pisé and stabilized earth, , Donhead,
http://www.staff.city.ac.uk/earthquakes/MasonryAdobe/ImprovedAdobe.html