1

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:

2

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.

3

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

5

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

9

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

10

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

11

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.

12

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