An investigation on the potential of mud as sustainable building material in the context of Kerala

Abstract

A house is made of building blocks but a home is made of hearts. In today's busy world, everybody is striving hard to make both ends meet in having a suitable and sustainable shelter for a healthy living. In the past few decades, cement and concrete have conquered the construction industry to such an extent that common man has forgotten to think of any alternative natural building material. On one side world is facing serious issues regarding carbon emissions, health issues generated from improper waste disposal while on the other side it is giving way to marvellous sky scrapers made of non-eco-friendly materials. Kerala has been always mentioned as God's own country for years, but the same credit can be truly achieved only if Keralites also practise building construction based on natural materials like mud that are sustainable to our environment. This paper is an attempt to investigate the potential of mud as a sustainable material in the context of Kerala.

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nt. J. Energy Technology and Policy, Vol. 13, Nos. 1/2, 201
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Copyright © 2017 Inderscience Enterprises Ltd.
An investigation on the potential of mud as
sustainable building material in the context of Kerala
M.S. Lekshmi*, Subha Vishnudas and
Deepa G. Nair
Faculty in Civil Engineering,
Division of Civil Engineering,
School of Engineering, CUSAT,
Kochi – 682 022, Kerala, India
Email: lekshmi.silas@gmail.com
Email: v.subha@cusat.ac.in
Email: deepagnair@cusat.ac.in
*Corresponding author
Abstract: A house is made of building blocks but a home is made of hearts. In
today’s busy world, everybody is striving hard to make both ends meet in
having a suitable and sustainable shelter for a healthy living. In the past few
decades, cement and concrete have conquered the construction industry to such
an extent that common man has forgotten to think of any alternative natural
building material. On one side world is facing serious issues regarding carbon
emissions, health issues generated from improper waste disposal while on the
other side it is giving way to marvellous sky scrapers made of non-eco-friendly
materials. Kerala has been always mentioned as God’s own country for years,
but the same credit can be truly achieved only if Keralites also practise building
construction based on natural materials like mud that are sustainable to our
environment. This paper is an attempt to investigate the potential of mud as a
sustainable material in the context of Kerala.
Keywords: mud construction; mud stabilisation; fibre reinforced mud; rammed
earth technique; interlocking mud blocks; Kerala.
Reference to this paper should be made as follows: Lekshmi, M.S.,
Vishnudas, S. and Nair, D.G. (2017) ‘An investigation on the potential of mud
as sustainable building material in the context of Kerala’, Int. J. Energy
Technology and Policy, Vol. 13, Nos. 1/2, pp.107–122.
Biographical notes: M.S. Lekshmi received her BTech in Civil Engineering
(2000) and MTech in Hydraulics Engineering (2002) from University of
Kerala, India. She has more than 13 years of teaching experience and has
worked in four reputed engineering colleges in Kerala, India. Currently, she is
working as an Assistant Professor in Division of Civil Engineering, School of
Engineering, Cochin University of Science and Technology, India and pursuing
her part time PhD under the same university. Her areas of interests are
hydraulics engineering, geotechnical engineering and sustainable building
materials. She is a life member of Indian Society of Technical Education
(ISTE) and an Associate Member of Institution of Engineers, India (IEI). She
has attended several national and international seminars, conferences and
workshops and has presented papers in national and international journals and
conferences. In addition, she has chaired and co-chaired national and
international seminars.

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Subha Vishnudas graduated with a BTech in Civil Engineering from Mahatma
Gandhi University, India in 1991 and took her Master’s degree form Kerala
University in 1995. She attained PhD from Delft University of Technology,
Netherlands in 2006. She has more than 16 years of teaching experience and
has published about 28 research publications in International journals and
conferences. She has visited many foreign countries like USA, Germany etc.
for presenting research papers in International conferences. She has also
delivered many invited talks and also chaired and co-chaired national and
international conferences and is also a reviewer of several international journals
and conferences. In addition she has professional membership in many
technical bodies like IGS, ISTE, NCMRI (Trivandrum), ISSE and EWRA.
Presently she is guiding about six research fellows for the PhD program while
working as an Associate Professor in the Division of Civil Engineering, School
of Engineering, CUSAT.
Deepa G. Nair graduated with a BTech in Civil Engineering from Kerala
University (1992) and took her Masters in Habitat Technology from Bitspilani
(1995). She attained PhD from Delft University of Technology, Netherlands in
2006. She has more than 15 years of teaching experience and five years of
industrial experience. Her areas of interests are sustainable building materials
and affordable housing. She has published about 24 research publications in
international journals and conferences. She has visited many foreign countries
like Spain, Tokyo etc., for presenting research papers in international
conferences. She has delivered many invited talks and chaired and co-chaired
national and international conferences. In addition, she has obtained
professional membership in many technical bodies like ISTE, IEI etc.
Currently, she is guiding about nine research fellows for PhD programme while
working as Associate Professor in Division of Civil Engineering, School of
Engineering, CUSAT, India.
1 Introduction
“Earth has enough to satisfy every man’s need, but not his greed.”
– Mahatma Gandhi
A sustainable shelter is inevitable for a greener future. Earlier people lived in houses
constructed by themselves using locally available materials in nature. Thus, mud, a soft,
sticky matter resulting from the mixing of earth and water became the most common
material for construction. Mud was being used either in its raw nature for wall
construction or in the form of mud blocks. It was also used as mortar for binding the
building blocks, for plastering the walls and also for flooring in ancient times.
The potential of mud as a building material has been very much explored in the
ancient times and it is still being practised in many of the European, Arab and Egyptian
countries.
Mud architecture began in Egypt and developed to its full extent alongside the Nile
(Capaldi, 2011). In Syria, the main construction unit was brick composed of 75% earth,
20 % straw (corn or barley) and 15% water and the mortar used was fine earth kneaded
with water adding corn straw and barley as reinforcement. But, the use of
mud bricks has disappeared in most of the countries. The reason behind the

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disappearance of this technique is the emergence of new, more performing materials
(http://www.medacorpus.net/arb/fitxes/F2/eng/A07_SY.pdf).
Mud is a good thermal insulating material in itself. Due to its excellent thermal
regulating property ample comfort was experienced by the inhabitants residing in mud
houses. It is a natural cost-effective material possessing zero embodied energy. Almost
all constructions done using concrete can be done with mud too. Instead of steel
reinforcements, bamboo can be used as reinforcements in mud structures. Despite the
above advantages, the concept of mud housing is gaining only slow popularity.
In the state of Kerala, India, mud was the major construction material till the
beginning of 20th century (Gopakumar, 2010). Most of the ancient palaces of Kerala
about 100 years old were made of timber and laterite. Almost all traditional houses in
Kerala (Tharavadu) were made with laterite blocks plastered with mud and cow dung.
Later on with the advent of cement and concrete, the mud houses slowly gave way to
concrete and steel to such an extent that today mud houses are rare in Kerala apart from
the existing traditional mud houses. As per the census of India the use of traditional
materials (mud, laterite and lime) for walls in Kerala decreased from 63.7% in 1961 to
30.4% in 2001 (Nair, 2006). The census data is a clear evidence of the slow
disappearance of mud houses in Kerala.
The objective of this paper is to investigate the reasons behind the decline of the
popularity of mud construction in the context of the state of Kerala, India. The
methodology adopted for the study consists of literature review, interview with practicing
architects and engineers and case studies of their projects.
2 Mud construction practices
2.1 A review
Mud has been used as the main building material from time immemorial in different
forms such as mud blocks, mud walls and mud plaster. It is a fact that the world’s first
skyscraper was built of mud bricks. The Ziggurates of Mesopotamia (3000-2000 BC) and
The Great Wall of China (206 BC) are examples of wonders of the world made with sun
dried mud blocks. The Great Mosque Djenne, Mali, Africa built in 1907 is the largest
mud brick building in the world (Kaushik, 2012). A case study conducted by Papayianni
and Stefanidou (2007) on the durability aspects of ancient mortars of the archaeological
site of Olynthos revealed that most of the ancient structural mortars were mud mortars.
Even though the microscopic analysis showed the presence of few shrinkage cracks
located around the aggregates and inside the binder paste, the mortar structure was found
quite solid.
Coming to the Indian scenario, the construction of mud brick houses was first
initiated in the ancient age during the time of Indus valley civilisation. Houses were also
incorporated with the proper drainage system using earthenware pipes (Architecture:
Mud Brick Houses and Step Wells, http://www.indiaonline.in/about/Profile). Other
examples of magnificent mud construction are Adisakthi theatre and guest house in
Pondicherry. According to Laurie Baker around 58% of all buildings in India today are
made of mud brick, and among them some are as many as 50 to 100 years old [Stephanie,
(2003), http://www.satyamag.com/apr03/miller.html]. Auroville Earth Institute in
Pune is conducting research on Poured Earth where earth in proper consistency

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can be poured directly into the wall frame work (http://www.earthauroville.com/
pouredearthresearch_en.php).
The State of Kerala also hosts numerous mud constructions. The Banasura Hill
Resort, the largest mud resort in Asia with the bewitching backdrop of Banasura hills, is
18 km away from Mananthavady in Wayanad District (Gopakumar, 2010). Most of the
tribal houses in this region are made with wattle and daub technique of mud construction.
Mud can function as a flooring material, walling material and roofing material in a
building in different forms. While it can decorate floors and roofs in the form of tiles it
can function as walls either as blocks or as stabilised earth.
2.2 Mud for masonry walls
Mud can be used either in the form of building blocks or can be applied directly to
construct walls.
The prevailing common techniques of mud wall construction are
1 cob technique
2 rammed Earth technique
3 wattle and Daub Technique
4 compressed Earth and SMB.
The word ‘cob’ comes from Old English root meaning ‘a lump of rounded mass’. It is a
traditional building technique using hand formed lumps of earth mixed with sand and
straw. Cob is easy to learn and inexpensive to build (Sruthy, 2013). Rammed earth is a
clay soil compacted into a formwork. Nowadays, stabilised mud is used for rammed
earth. Wattle and daub construction consists of a bamboo framework with mud filling
(Jagadish, 2013). A study conducted on the compressive strength characteristics of
cement stabilised rammed earth walls by Jayasinhe and Kamaladasa (2007) indicate that
laterite soils stabilised with about 6% cement can be used as a wall material for single
storey houses in tropical climatic conditions.
One of the earliest methods of using earth as a raw material was in the form of mud
bricks. Mud was filled in mould, compacted manually, dried in sun and cured under
shade to make mud bricks. Taking into consideration the drawbacks of raw mud, cement
stabilised soil blocks properly compacted with manual or hydraulically operated
machines, were used as individual building units. Interlocking stabilised mud blocks
(SMB) are the latest innovation in this field.
The incorporation of fibres into soil to prevent shrinkage cracks also dates back in
history. The Ziggurates of Mesopotamia was constructed with clay bricks reinforced with
woven mats of reeds and plaited ropes. The sections of western part of The Great Wall of
China had clay reinforced with tree branches. Dey (2014) mention that soil mixed with
wheat straws was common in Indian villages.
In this context, Adobe, a natural building material made from sand, clay and water
with some kind of fibrous or organic material needs special mention (Sruthy, 2013). Use
of these sun-dried blocks dates back to 8000 BC (Blondet and Villa Garcia, 2011). Marin
et al. (2010) conducted studies on clay-based soil stabilised with natural polymer and
fibre and found that organic fibres check the development of shrinkage cracks in Adobe.

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Numerous studies have been conducted on the feasibility of using fibres as
reinforcements in mud construction. Binici et al. (2005) investigated on the feasibility of
fibre reinforced mud brick as a building material and found that fibres distributed
randomly possess more compressive strength than those in longitudinal and transverse
directions.
The selection of construction techniques depends upon many factors such as the
availability of suitable mud for each method, availability of skilled labour, transportation
facilities and climatic conditions. Cob walls are generally used in consideration with
aesthetics than functionality whereas rammed earth walls give priority to structural
aspects of the building. Wattle and daub construction is more suitable for earth quake
prone area. Fibre reinforcement in rammed earth construction is suitable for improving
the strength and durability. Adopting the suitable soil and proper methods of stabilisation,
it is possible to construct two storey mud buildings with rammed earth technique and two
or more storeys with compressed earth blocks.
2.3 Mud as masonry mortar
Mud mortars were used traditionally for a longer period of time. Later on lime and
cement mortars came to be used conventionally. While cement mortars gave greater
strength and durability, lime mortars gave better finish to the walls. Reddy and Gupta
(2006) investigated the compressive strengths and elastic properties of stabilised mud
mortar masonry using cement mortar, cement-lime mortar and cement-soil mortars and
came to the conclusion that an increase in cement content of a cement-soil mortar from
10%–15% results in about 20% increase in the masonry compressive strength.
Unlike the conventional plasters, mud possesses a unique property known as
breathability, an important factor in any wall system. If the resistance to water
penetration and termite attack is properly ensured mud is the most suitable and
sustainable material for a healthy living. Chandra et al. (1998) made a study on the use of
cactus in mortars and concrete. It was seen that cactus extract increases the plasticity of
the mortar and improves water resistance and freeze-salt resistance. Painting of the
concrete with this extract has also shown improved water resistance. Mud walls can also
be painted with cactus or similar cellulose extracts to improve water resistance without
damaging the breathability of walls.
The use of non-erodible mud (NEM) plaster was an innovation in this context.
Central Building Research Institute, Rourkee conducted experiments on the effectiveness
of NEM. The soil for NEM consists of 40%–45% sand, 20%–25% clay and remaining
silt or loam. To this wheat straw 6% by weight of dry soil is added. The purpose
of wheat straw is to act as networking agent to prevent cracking. Bitumen of
80/100 grade penetration and kerosene oil is mixed in the proportion of 5:1 preparing cut
back, i.e., 53.25 kg of bitumen and 10.5 litre of kerosene oil for every cubic metre of dry
soil. Bitumen is heated till it melts and this molten bitumen is slowly added to the
kerosene oil kept in a separate container, keeping the whole mixture stirred until the
whole of bitumen is added. The bitumen cut back so prepared is added to the mud mortar
prepared earlier in the traditional manner (Central Building Research Institute,
cbri.res.in/CSIR-800/.../WebTech/RBEA3-NonErodableMudPlaster.pdf). The presence
of bitumen makes the mortar flexible. This is effective in checking the termite attack also.
The plastered wall will have a black dotted appearance of bitumen.

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Normal plastering can be done with cow dung, activated carbon and fenugreek seeds
which are all available naturally. Mud walls constructed using rammed earth technique
presents a rough textured appearance on removing the rammed earth form work .The
walls can be given a smooth appearance by the technique of smooth plastering.
3 Mud stabilisation
The major drawbacks with raw mud are its vulnerability to erosion, termite attack and
development of shrinkage cracks. Hence, it has to be properly stabilised to improve its
physical and mechanical properties using natural or chemical stabilisers. In ancient days,
cow dung was used as a stabiliser to protect the mud walls and to enhance the durability.
Conventionally, lime and cement are used as stabilisers along with mud depending upon
the soil composition.
Fibres used as reinforcement in mud can be used for different purposes in different
forms. It can be used for reinforcing mud blocks or mud walls and for reinforcing mud
mortar to prevent cracking. Hejazi et al. (2012) in their study found that plant roots,
shredded tyres and recycled waste fibres can also be used as reinforcement in addition to
factory manufactured synthetic fibres. It was also observed that shrinkage crack reduction
and hydraulic conductivity of compacted clay soil have been increased with an increase
in fibre content. Recent studies show that the incorporation of fibres into the soil matrix
would enhance the strength and durability of soil mixes.
Mud can be applied as a plaster material for straw bale buildings, an eco-friendly
concept. Ashour and Derbala (2010) made a study on the shrinkage of natural plastering
materials for straw bale buildings affected by reinforcement fibres and drying. They
observed that the reinforcement fibre had greater effect on the drying shrinkage than
sand. Marin et al. (2010) found that the compressive strength of stabilised soil specimens
increases with the addition of natural polymer and fibre. Kaci et al. (2011) made a study
on the adhesive and rheological properties of fresh fibre reinforced mortars using probe
tack test and came to the conclusion that the addition of fibres leads to the decrease of the
mortar adherence to the support.
In further studies of fibre reinforced mud, it is necessary to discuss the type of
reinforcement and the effective orientation of fibres with respect to the soil strength.
4 Interviews and case studies
To keep in line with the objective of this study, a thorough analysis of the present status
of mud construction in the state of Kerala was necessary. Interviews were conducted with
selected experts practising mud construction. This was followed by case studies on their
works to confirm the real situation in the field.
4.1 Interviews
Practising architect (G. Shankar), practising engineers (P.K. Sreenivasan and
P.I. Aravind) and an academician (Architect Eugene Pandala) were identified as experts
for the interview.

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Table 1 Details of experts in mud construction interviewed
Sl. no. Name of expert Designation and address Experience in the field
of mud construction Major projects Date of interview
1 G. Shankar Founder and Director, Habitat
Group of Technology,
Thiruvananthapuram and
Padmasree winner
More than 20 years Earth building in Dhaka
(6 lakh sq. ft.), low cost township at
Sirumugai, Coimbatore
April 12, 2014
2 P.K. Sreenivasan Founder and Director,
Vasthukam – the organic
architects, Thrissur
More than 20 years Aadisakthi (5,300 sq. ft.– theatre
campus in Pondicherry, mass housing
of 10 mud houses (each 357 sq. ft.)
for Kairali tribal colony, Wayanad
District
May 6, 2014
3 Aravind P.I. Project Engineer, Kereala
State Nirmithi Kendra
(KESNIK), Thiruvananthap
uram
More than 20 years Implementation of cost effective
techniques such as filler slab roofs,
mud press blocks, stabilisation of
laterite soil for blocks
May 11, 2014
4 Eugene Pandala Professor, Department of
Architecture, T.K.M. College
of Engineering, Kollam
More than 30 years Bodhi (residential building), Banasura
Hill resort, Wayanad
April 16, 2014

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Table 2 Inference from interviews
Experts 1 2 3 4
1 Technology adopted
for walls
Interlocking mud blocks Rammed earth technique,
exposed laterite blocks
Rammed earth technique Rammed earth
technique, cob technology
2 Composition of mud
preferred
15% gravel, 50% sand,
15% silt and 20% clay
Gravelly soil for
rammed earth walls
Red colour mud with higher iron
content; 70% sand and 30% clay
80% sand and 20% clay
3 Field tests Yes Yes Yes Yes
4a Stabilisation methods
used
Cement or lime depending
upon the composition of soil
Cement in the ratio one
part of cement: 50 parts of mud
Cement or lime 5% cement
4b Traditional methods Cow dung, activated
carbon, fenugreek seeds
Rice husk, neem seeds,
methi seeds, fenugreek seeds
Cow dung, neem seed oil Bull’s blood, pig’s urine, sticky
weeds, fish with slimy secretion
4c Suitable reinforcement
materials in mud
Straw, animal hair,
wool and synthetic fibres
Rice husk, straw Natural fibres such as sisal,
banana, bagasse, bamboo, straw
Non-degradable materials
5 Type of plaster used Non-erodible mud
plaster for inside walls
Cement plaster for outside walls,
mud plaster for inside walls
Mud p laster Lime o r mud plaster
6a Drawbacks identified Erosion during rainy
seasons and termite attack
Erosion during rainy
seasons and termite attack
Erosion during rainy
seasons and termite attack
Erosion during rainy
seasons and termite attack
6b Remedial measures Use of crushed
neem seeds, NEM plaster
Provide roof and shade overhang
to about 75 cm, chemical
pesticide, roasted fenugreek
seeds, crushed neem seeds for
termite attack
Provide eaves projection about
2 ft. over the walls and
using NEM plaster coated
with neem seed oil.
Stabilisation with
5% cement, bitumen
7 Frequency of
maintenance
Maintenance not required Not required Not required Not required
8 Precautions, if any Soil with organic
smell has to be discarded
Up to sill height cement plaster
can be given to protect timber
floors and tiles. Alignment
should be properly checked
for rammed earth construction.
Smooth coat should be applied
only after rough coat had dried.
Mud walls have to be completed
before rainy season.
Construction should be
completed before rainy season.
Natural fibres pose a problem
of decay and degradation.
9 Economy 20%–25% cost
reduction in structure
15%–20% cost reduction 20%–25% cost reduction,
more economical in the
case of mass housing
40% cost reduction

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A questionnaire survey was also conducted among the experts on the relevant aspects of
mud construction. Table 1 shows the details of experts and their work. The inference
from the questionnaire survey with the experts is summarised in Table 2.
It can be observed from Table 2 that mud when properly stabilised and reinforced can
overcome its draw backs and can function as an excellent building material. More
economy can be achieved if the required quantity of mud is dug from the site itself.
4.2 Case studies
Selected projects constructed by the experts were identified and taken for case study.
Among these, four houses are made of interlocking mud blocks under taken by Habitat
Group in Thiruvananthapuram and the remaining three are constructed using rammed
earth technique. Among the rammed earth buildings, the first one is the residential
building by P.K. Sreenivasan at Thrissur, second one is a demo mud house constructed
by KESNIK in their campus at Thiruvananthapuram and the third one is a 3D studio by
Eugene Pandala at Thiruvananthapuram. In this case study, a residential building made of
interlocking mud blocks and three rammed earth buildings have been presented. A
similar questionnaire survey was conducted among the inhabitants of the mud houses to
check their comfort level and problems if any, while residing in these houses.
4.2.1 Expert 1 – case study 1, Thiruvananthapuram
4.2.1.1 Year of construction: 2004
The Habitat Group uses inter blocking mud blocks as their latest technique of
construction. The residential building selected for case study at Thiruvananathapuram
was made of stabilised interlocking mud blocks and has completed 11 years (Figure 1).
The outer walls were left unplastered and one inside wall was plastered with NEM
plaster. All other inner walls were cement plastered and painted.
Figure 1 Residence with stabilised inter locking mud blocks (see online version for colours)

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The response from the inhabitants reinstate that mud is an excellent thermal regulator. It
keeps the house warm in winter and cool in summer. In addition to this, the positive
energy which they feel while residing in these houses makes them energetic and
enthusiastic in their day-to-day activities.
4.2.2 Expert 2 – case study 2 (Anpu, Thrissur)
4.2.2.1 Year of construction: 2004
The residential building of P.K. Sreenivasan itself ‘ANPU’ is taken for the case study. It
was constructed in a traditional Nalukettu style (Figure 2) with an area of 1/900 sq. ft.,
completed 11 years and the cost of construction was Rs. 430 per sq. ft. It was constructed
using rammed earth technique. An overlying coat of smooth plaster was applied over the
rough texture in different shades of colours thus demonstrating the fact that it is possible
to give variety of colours to inner walls by the art of smooth plastering. Stabilisation was
done with cement and reinforcement was done with rice husk. The smooth plaster coat
was made possible with mud, sand, cement and lime. Some portion of the flooring was
done with wooden planks retrieved from an abandoned house and rest of the flooring was
done of a material made with hibiscus flowers, coconut shells, charcoal, kaajal and
cement to give a smooth mirrored finish.
Figure 2 Anpu (a residence at Thrissur) (see online version for colours)
The inhabitants feel great thermal comfort within the building. The smooth plastered
walls give a soothing pleasant earthy smell refreshing the air within the building.
Normally, people refrain from the concept of mud buildings due to the rough texture
and dark shades within the rooms. Sreenivasan’s smooth plastering technique is an
answer to the above queries. A variety of natural colours may be made possible like deep
red, soft yellow, yellow ochre, chrome yellow, muted brownish gold by mixing different
textures of mud. He has demonstrated the same in his own residence. Now, the demand
for mud buildings with smooth plaster has increased in this locality.

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4.2.3 Expert 3 – case study 3 (Demo house, KESNIK)
4.2.3.1 Year of construction: 2012
The demo house in the KESNIK campus is about 650 sq. ft. in area (Figure 3) and was
constructed with the purpose of creating awareness among people in promoting mud
construction in the state of Kerala. Rammed Earth technique has been adopted for the
construction. Plastering was done with NEM plaster coated with neem seed oil and eaves
projection of 2 ft. was provided around the walls. The construction cost came to about
7 lakhs and the house was completed in two years.
Figure 3 Demo house at KESNIK (see online version for colours)
4.2.4 Expert 4 – case study on Revathy Kalamandir, Thiruvananthapuram
4.2.4.1 Year of construction: 2013
Revathy Kalamandir, a 3D studio building at Thiruvananathapuram [Figure 4(a),
Figure 4(b), Figure 4(c)] in rammed earth technique is a master piece of Eugene Pandala.
It has an area of about 12,000 sq. ft., constructed from the soil available at the nearby site.
The walls are rough and are left un-plastered. Stabilisation was done with 5% cement to
check water penetration and termite attack. The pillars are carved aesthetically using cob
technology. Lot of ventilation and jally works are given for proper air circulation. Cavity
wall required for the studio portion was done using rammed earth technique. Cement
plastering was given for the soffit of arches, wall and column bases and top surface of
stairs. The building stands out as an example of the effective utilisation of mud
minimising the use of cement and steel. During its construction phase itself, the building
was exposed to the vagaries of nature for eight long years. Yet, the structure withstood all
adverse climatic conditions and still remains free from cracks and termite attack,
radiating its earthy colour in the lush green KINFRA campus.

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Figure 4 (a) Revathykalamandir (3D studio), Thiruvananthapuram (b) Pillars in cob technology
(c) Corridor arches (see online version for colours)
(a)
(b)
(c)

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5 Discussion and inference
The major findings from the literature review, interviews and case studies are discussed
in this section. Literature review reveals that mud is a versatile and sustainable material
for construction. Yet, there is scope for a detailed scientific study on mud as a
construction material. Raw mud has to be properly stabilised with traditional (cow dung),
conventional (cement or lime) or artificial stabilisers (bitumen) which when reinforced
with either natural or artificial fibres impart better strength and durability to the structure.
The discussion with experts suggests that any burnt material is unsuitable for building
construction. The walls of the houses should be able to breathe. Stabilisation with 5%
cement is enough to make the mud walls strong and resistant to termite attack and water
penetration. Other methods of tackling termite attack are through NEM plaster, roasted
fenugreek seeds and crushed neem seeds. NEM plaster can also check erosion of mud
walls. Lime plastering provides better finish and good appearance.
It has been found from case studies that majority of Keralites who wish to have mud
houses prefer stabilised interlocking mud blocks to rammed earth technique. The reason
for preferring interlocking mud blocks may be imparted to its easy procurement, good
finish, greater strength and durability. Since it is available as a finished product, its cost is
also high about Rs. 24–28 per block. It was also evident that real group of rustic earth
lovers still prefer rammed earth technique leaving a natural rough earthy appearance to
their buildings.
The added advantage of mud constructions is that plastering is optional. Most of the
customers prefer to leave the walls un-plastered in order to expose the beauty of laterite
blocks or stones. By doing so, economy in plastering can also be achieved. If required,
the walls can be plastered with mud itself. It is possible to give different shades of
colours to the mud walls by mixing different textures of mud collected from various
localities. The cost comparison of structure alone reveals that about 20%–25% in
economy can be achieved with mud walls when compared with brick walls with cement
plastering.
6 Conclusions and recommendations
This study about the potential of mud as sustainable building material, identified some of
the positive aspects for choosing mud as a construction material and those are listed
below:
1 Environment friendly: Mud is a fresh unpolluted material posing zero embodied
energy staying close to nature. Anything built of mud can be reused without
affecting the environment.
2 Health aspects: Due to the unique property of breath ability, mud buildings ensure
better health and impart positive energy to its inhabitants.
3 Thermal comfort: The response from the inhabitants assures that mud is an excellent
thermal regulator. Mud buildings can be a solution to reduce global warming. There
is a greater demand for mud houses now considering the cooling effect within the
building.

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4 Economy: About 20%–25% economy in structure is achieved with mud buildings
compared to brick walls with cement plaster.
Even with these advantages mud buildings in Kerala gave way to concrete structures.
This study points also out some important facts as the reasons towards the decline of mud
constructions in Kerala. They are grouped under socio cultural factors and technological
factors as follows:
1 Socio cultural factors: Acceptance, awareness and availability are considered under
socio cultural factors.
a Acceptance: Poor acceptance of mud construction in Kerala is mainly due to the
prolonged construction period and availability of skilled labour. Mud
construction is not advisable in rainy season and hot summer seasons. Kerala
receives heavy rainfall from the two major rainy seasons – South West monsoon
period (May–August) and North East monsoon period (October–November).
Summer period starts during the beginning of March and extends till the mid of
May. Hence, it is difficult to schedule the construction period. This has led to
the prolonged construction period of many of the existing buildings.
b Awareness: Lack of proper awareness and unnecessary fear among people about
the durability of mud buildings make them refrain from mud construction.
c Availability: People in general prefers materials and methods, which are readily
available and easily accessible. Hence, they are reluctant to shift from the
conventional materials of construction (bricks, cement, concrete blocks, etc.).
This is justified by the case studies which reveal the superior preference of
interlocking mud blocks over other technological options which are cast in-situ
type.
2 Technological factors: Even though mud constructions are strong and durable people
are suspicious about the reliability aspects. Most of the technology is not accessible
to common man. Lack of skilled labour may result in poor aesthetic appearance with
bulges and cracks demanding proper maintenance.
Taking into consideration all the above aspects, this study recommends the following
measures which could be implemented to overcome the issues responsible for the decline
of mud buildings and to promote the existence of mud buildings in Kerala. These
measures are discussed below.
1 Selection and testing of soil: The soil should be selected after conducting relevant
field tests in the presence of a practising engineer. Top soil should be avoided.
2 Technology: Based on the nature of the soil and client’s choice a suitable technology
(cob, rammed earth, wattle and daub, inter locking mud blocks) may be adopted for
the mud building. If the soil at the site does not match the requirements, it has to be
transported from nearby sites.
3 Stabilisation: Depending on the soil composition, proper stabilisation is to be done
with cement, lime, cow dung, etc. Fibre reinforcement with coir fibres, straw fibre,
banana fibre, bagasse fibre, etc., will check shrinkage cracks.
4 Planning: The construction of mud buildings has to be carefully planned so as to
avoid too wet and too dry climates.

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n investigation on the potential of mud as sustainable building material 121
5 Finishing: The construction using interlocking mud blocks presents a neat finish,
hence no need for external plastering. But for all other techniques smooth plastering
with mud can be done over the rough textured walls to get a smooth and glossy
appearance. Sometimes one or two coats of lime plaster can also be applied for a
brighter finish.
6 Precautions: At least one skilled mason should be there to supervise the entire work.
While erecting rammed earth frame work care should be taken to keep the alignment
vertical otherwise the wall will be inclined once the frame work is removed. Eaves
projection of 2 ft. should be provided throughout the walls. Proper measures for
tackling termite attack and erosion as mentioned in Table 2 may be implemented.
Anyhow, there is a light at the end of the tunnel, that Kerala’s building architecture has
showed signs of heading backwards to earth and nature in the past 15 years. Eminent
architects of Kerala, with their untiring effect, have retrieved the ancient practice of mud
housing in Kerala and have proved that the properly modified mud is the most suited
material for building construction. Yet, wide popularity is essential in retrieving the lost
earthen buildings back to Kerala.
“It is concluded that the potential of mud as a sustainable building material is
undoubtful and immense provided that it should be promoted and practised
with prime importance given to the concepts of sustainable development.”
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