A sustainability approach to standards for rammed earth construction in Bhutan

“I hereby declare that, except where specifically indicated, the work submitted herein is

my own original work”

A sustainability approach to standards for

rammed earth construction in Bhutan

by

Zareen Sethna (CL)

Fourth-year undergraduate project

Group D, 2007/2008

A sustainability approach to standards for rammed earth construction in Bhutan

Zareen Sethna, Clare College i

Contents Contents Contents Contents

Technical AbstractTechnical AbstractTechnical AbstractTechnical Abstract .................................................................................................................................................................................................................................................................................................................................................................................................................................................................... iiiiiiii

1111 IntroductionIntroductionIntroductionIntroduction ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 1111

1.1 Context ....................................................................................................................................... 1

1.2 Project Objectives ...................................................................................................................... 4

2222 MethodologyMethodologyMethodologyMethodology .................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 6666

3333 Data collectionData collectionData collectionData collection ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 10101010

3.1 Initial literature review ........................................................................................................... 10

3.2 Semi-structured Interviews .................................................................................................... 10

3.3 Site visits and informal interviews ........................................................................................ 12

3.4 Soil testing .............................................................................................................................. 15

3.5 Detailed literature review ....................................................................................................... 16

4444 FindingsFindingsFindingsFindings ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 18181818

4.1 Is there a need?...................................................................................................................... 19

4.2 What is needed? ..................................................................................................................... 23

4.3 What is known? ...................................................................................................................... 26

4.3.1 Materials ................................................................................................................................. 27

4.3.2 Design ..................................................................................................................................... 33

4.3.3 Construction ........................................................................................................................... 39

5555 Conclusions and RecommeConclusions and RecommeConclusions and RecommeConclusions and Recommendationsndationsndationsndations .................................................................................................................................................................................................................................................................................................................................... 40404040

6666 ReferencesReferencesReferencesReferences .................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 46464646

7777 Appendix AAppendix AAppendix AAppendix A ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 48484848


Zareen Sethna, Clare College ii

Technical AbstractTechnical AbstractTechnical AbstractTechnical Abstract

Background and motivation for wBackground and motivation for wBackground and motivation for wBackground and motivation for workorkorkork

Rammed earth has traditionally been used extensively in Bhutan and can be seen as a

highly sustainable building material. The exceptionally low material costs of rammed

earth construction give it a significant economic advantage over alternative materials,

such as brick, stone and cement, despite the additional costs incurred in using a more

labour intensive method. The high thermal mass of rammed earth reduces the energy

demand of buildings and the energy input required in production and transportation of

the material is inherently low: hence rammed earth is environmentally sustainable. Two

of the thirteen traditional arts and crafts of Bhutan, dozo (masonry) and shingzo

(woodwork), are inherent in the construction of rammed earth buildings and hence in

promoting the continuation of rammed earth these crafts will also be preserved.

Despite its many advantages, rammed earth construction in Bhutan has seen a steep

decline in recent years. Although there are many reasons behind this trend, the lack of a

code of practice in particular appeared to be acting as a barrier to rammed earth

construction in urban areas. The project therefore aspired to facilitate the continued use

of this highly sustainable material by conducting the research necessary to the

development of an appropriate code of practice for rammed earth construction in Bhutan.

ResearchResearchResearchResearch

Three key research questions were identified and corresponding research objectives

developed:

The research strategy was designed around the specific nature of each objective. Certain

research methods were suited to multiple objectives and hence research questions were

pursued in parallel through a combination of primary and secondary research methods.

These included semi-structured and informal interviews, site visits, soil testing and a

detailed literature review of Bhutanese codes, Eurocodes and rammed earth guidelines.

3. What is

known?

2. What is

needed?

1. Is there a

need?

Verify whether there is a need in Bhutan for

standards on rammed earth

Determine what is required of a code of

practice in Bhutan

Establish the state of knowledge on rammed

earth in Bhutan and internationally


Zareen Sethna, Clare College iii

FindingsFindingsFindingsFindings

1. Is there a need?

A code of practice on rammed earth construction does not currently exist in Bhutan and

such a code would facilitate the continued use of rammed earth in urban areas. Despite

there being a wealth of literature on rammed earth internationally, there is no existing

code of practice which is appropriate for use in Bhutan.

2. What is needed?

The research shows that the code should cover the same material, design and

construction considerations as are dealt with in national codes on rammed earth

construction from other countries, but at an appropriate level of detail; this should be

sufficient to enable the construction of safe, simple buildings but should not extend to

the level of detailed structural calculations.

3. What is known?

The materials used for rammed earth construction in Bhutan conform approximately to

the specifications of previous research literature. Traditional Bhutanese design and

construction methods were found to be conservative with respect to the design criteria of

various national standards. The exception to this finding is in relation to seismic design

features which are recommended for rammed earth buildings yet are not seen in

traditional rammed earth buildings in Bhutan.

4. Overall findings

A code of practice can be written on the basis of traditional Bhutanese design and

construction practices without contravening recommendations made by the various

national codes on rammed earth construction reviewed. This is with the exception of

considerations relating to seismic design, where further expert advice should be sought in

order to find a safe balance between traditional practice and conventional earthquake

resistant features. By incorporating the flexibility to enable mechanical ramming and

reduce wall thicknesses, the code could address some of the disincentives to

constructing rammed earth buildings; however in doing so it will stray from traditional

practices. International norms must be more strictly adhered to if this approach is taken,

since the wealth of traditional knowledge that currently provides the crucial safety factor

in Bhutanese rammed earth buildings will become redundant.


Zareen Sethna, Clare College 1

1111 IntroductionIntroductionIntroductionIntroduction

Any work of research must first justify its conception and objectives by showing there to

be a gap in the academic literature and, particularly in engineering, demonstrating a

distinct social or environmental need. This section therefore positions the project within a

scientific context and discusses the real need to which it responds.

1.11.11.11.1 ContextContextContextContext

1.1.11.1.11.1.11.1.1 Rammed earth construction in BhutanRammed earth construction in BhutanRammed earth construction in BhutanRammed earth construction in Bhutan

Rammed earth has traditionally been used extensively in Bhutan for the construction of

domestic, religious and administrative buildings. In recent years there has been a

dramatic reduction in the use of rammed earth. Whilst there are a number of

explanations for this trend there are also strong economic, environmental and social

incentives for the continued use of this highly sustainable technology.

Despite the increased labour costs associated with rammed earth it is invariably the more

economic option since the material costs of alternative construction materials are

substantial. Stone has been used widely in recent years, however given Bhutan’s fragile

landscape and unstable topography this trend was unsustainable and the National

Environment Commission (NEC) has now placed stringent limits on quarrying in Bhutan

and hence stone is becoming scarce and more expensive.

Cement, bricks and other construction materials often have to be transported long

distances hence incurring high environmental costs in addition to their embodied energy

which is invariably higher than that of rammed earth. They are also less appropriate to

the climate where hot sunny days and cold nights enable the high thermal mass of the

rammed earth to act to its utmost advantage.

Whilst most Bhutanese are keen to see their country develop they are also proud of their

traditions and in particular the 13 traditional arts and crafts of Bhutan, two of which, dozo

(masonry) and shingzo (woodwork), are inherent in the construction of rammed earth

buildings. There have been many attempts to document and encourage the revival of

traditional architecture and arts, however traditional construction appears to be in

decline.



1.1.21.1.21.1.21.1.2 The need for appropriate standardsThe need for appropriate standardsThe need for appropriate standardsThe need for appropriate standards

“The need for standards is not disputed”

Constructing Excellence (2006:2)

Standards are widely seen to “make life simpler and to increase the reliability and the

effectiveness” (http://www.bsi-global.com) of projects and hence improve the safety of

those pertaining to the built environment. In Bhutan there is an additional need; the lack

of standardisation appears to be acting as a barrier to rammed earth construction in

urban areas. In these areas where regulatory authorities exist rammed earth projects

have faced difficulties in obtaining insurance and planning permission. Although a

number of flagship buildings have been constructed, the lack of standardisation is

perceived to be preventing the construction of larger or multiple projects; many engineers

feel that without a code, rammed earth can only be used for one off buildings where

quality can be assured through close supervision.

Despite the interest in rammed earth construction in recent years there are relatively few

comprehensive standards on the method. However it is not so much the absence of

standards which is the justification behind this project, but rather the desire to provide

the engineering sector in Bhutan with an appropriate standard.

The concept of appropriacy can be traced back to the 1970s and the work of the

economist E.F Schumacher. In his last lecture in Caux he stated:

“If you want to be a good shoemaker, it is not good enough to make good

shoes...you also have to know a lot about feet”

New World News, 17 September 1977

This captures the essence of appropriacy; one size doesn’t fit all. In the same way as

Schumacher argues that modern western technologies are unsuitable for developing

countries, so this project is based on the premise that standards are also context

specific, and in assuming that they are universal we can do considerable harm. An

intermediate standard is hence required; one which improves on the baseline of no

standard at all, conforms to certain international norms, and yet focuses on delivering a



solution which meets the technical, social, economic and environmental requirements of

the situation (Francis & Mansell, 1988:44).

Based on these concepts, an appropriate code of practice can be regarded as one which

fulfils the following specifications:

• codify traditional practices rather than overrule them, and hence allow architects and

engineers to design buildings that can be constructed using traditional methods

• address the needs of the target audience in terms of style and content

• be sensitive to the social, environmental and economic issues relating to the

construction industry in Bhutan

• maintain the same breadth of coverage and technical rigour as codes used elsewhere

in the world.

• not only replicate but also develop current practices to incorporate relevant new

techniques and improvements



1.21.21.21.2 Project ObjectivesProject ObjectivesProject ObjectivesProject Objectives

In response to the apparent need for a code of practice the initial concept of the project

was “to produce an appropriate code of practice for rammed earth construction in

Bhutan”. However it is the research necessary to the development of such a standard

and not the production of the code itself which is the aim of this project. During the early

stages of the research it was perceived that there was a need to break this aim down

further:

The framework demonstrates the key research questions in the development of a code of

practice. This project includes the research activities and leaves the production of the

code for later work as it is not the remit of a 4th year project. Each research question

leads to a clearly specified project objective, these are described in greater detail below.

3. What is

known?

2. What is

needed? 1. Is there a

need?

Produce a

code

4Th Year Research Project

yes

no

Figure 1: Project frameworkFigure 1: Project frameworkFigure 1: Project frameworkFigure 1: Project framework

No project

3. What is

known?

2. What is

needed?

1. Is there a

need?

Verify whether there is a need in Bhutan for

standards on rammed earth

Determine what is required of a code of

practice in Bhutan

Establish the state of knowledge on rammed

earth in Bhutan and internationally

Research QuestionsResearch QuestionsResearch QuestionsResearch Questions

Research ObjectiveResearch ObjectiveResearch ObjectiveResearch Objectivessss



Verify Verify Verify Verify whether whether whether whether there is a there is a there is a there is a need in Bhutan for standards on rammed earthneed in Bhutan for standards on rammed earthneed in Bhutan for standards on rammed earthneed in Bhutan for standards on rammed earth

The project was conceived following a work placement with the Royal Government of

Bhutan’s Department for Urban Development and Engineering Services in the summer of

2007. This experience, combined with discussions with a development practitioner, led

to the initial perception of the need for a code of practice; however it was important to

verify that a code would be relevant in facilitating the continued use of rammed earth in

Bhutan.

Determine what is required of a code of practice in BhutanDetermine what is required of a code of practice in BhutanDetermine what is required of a code of practice in BhutanDetermine what is required of a code of practice in Bhutan

Once the need has been established it is necessary to develop an understanding of the

requirements of a code of practice in the context in which it will be used. This involved

determining who the target audience is, what their needs are and hence what form a

code should take.

Establish the state of knowledge on rammed earth in Bhutan and internationallyEstablish the state of knowledge on rammed earth in Bhutan and internationallyEstablish the state of knowledge on rammed earth in Bhutan and internationallyEstablish the state of knowledge on rammed earth in Bhutan and internationally

In order to produce an appropriate code of practice it was essential to capture the wealth

of knowledge on rammed earth construction that exists in Bhutan and gain an in depth

understanding of the issues surrounding it. A working knowledge of the existing literature

on rammed earth and codes of practice from other countries was also required for

comparative purposes and to improve on aspects of current practice such as those

relating to seismic design.



2222 MethodologyMethodologyMethodologyMethodology

This section lays out the principles behind the methods chosen in this study. Whilst in

concept a code of practice is seen as a highly objective tool by most engineers, the

process of its creation and the associated research involve a complex combination of

primary and secondary methods taken from both scientific and social science disciplines.

2.12.12.12.1 Appropriate methods to achieve research objectivesAppropriate methods to achieve research objectivesAppropriate methods to achieve research objectivesAppropriate methods to achieve research objectives

The research strategy was designed around the specific nature of each objective. Certain

research methods were suited to multiple objectives and hence research questions were

pursued in parallel as can be seen from the colour coded lines in the diagram above.

The first objective required two lines of enquiry: firstly does an appropriate standard exist

and secondly would a standard be useful? These were pursued through an initial

literature review and semi-structured interviews respectively. The interviews were also

used to ascertain what stakeholders require of a code of practice and what shortcomings

they find in the codes they use. This was then backed up by a detailed review of the

current codes in use in Bhutan and elsewhere in order to develop a detailed picture of

what is required of a code of practice (objective 2). A combination of informal interviews,

Comparative

analysis

Initial literature

review

Research methodsResearch methodsResearch methodsResearch methods

Site visits

Soil testing

Semi-structured

Interviews

Primary Primary Primary Primary methodsmethodsmethodsmethods

Secondary Secondary Secondary Secondary

methodsmethodsmethodsmethods

Informal

Interviews 3. What is

known?

2. What is

needed?

1. Is there a

need?

Research Research Research Research

QuestionsQuestionsQuestionsQuestions

Detailed

literature review

AnalysisAnalysisAnalysisAnalysis

Convergent

validation

Figure 2: Methodological FrameworkFigure 2: Methodological FrameworkFigure 2: Methodological FrameworkFigure 2: Methodological Framework



site visits and soil testing were used to generate an in depth understanding of Bhutanese

traditions and practices; these were then analysed with reference to the international

standards established from the detailed literature review.

2.22.22.22.2 Choice of methods appropriate to the contextChoice of methods appropriate to the contextChoice of methods appropriate to the contextChoice of methods appropriate to the context

In-depth interviews and detailed literature reviews formed key components of the

research as it was essential that the choice of methods be consistent with the ethos of

the project; namely in giving primacy to the needs and knowledge of people in Bhutan

and yet not neglecting the body of technical literature on the subject. Detailed data on

rammed earth construction was generated through site visits whilst soil testing enabled

comparison with other national standards; as well as giving the research credence within

the engineering community.

2.32.32.32.3 An inductive approaAn inductive approaAn inductive approaAn inductive approachchchch

The first objective would tend to indicate the use of deductive reasoning in that “the

hypothesis come[s] first” (Bryman 2001:8), however the study overall follows an inductive

approach in that it starts with “an area of study and allows the theory to emerge from the

data” (Strauss and Corbin cited in Bartlett, 2005:43). Inductive approaches are useful

when all the relevant concepts are not known, and where there is not a formal body of

theory from which to deduce hypotheses for empirical scrutiny (Bryman, 2001:5); this is

certainly the case in this area, both the preliminary literature review and subsequent

interviews confirmed that there has been very little work done on appropriate standards

for Bhutan.

2.42.42.42.4 A combination of methodsA combination of methodsA combination of methodsA combination of methods

Qualitative and quantitative research are differentiated on the basis of data types

employed: quantitative data is expressed numerically whereas qualitative data cannot be

expressed numerically (Strauss and Corbin cited in Bartlett, 2005:42). The study uses

both qualitative and quantitative methods, an approach which is often seen as

advantageous:

“Theory-building researchers typically combine multiple data collection

methods......of special note is the combining of qualitative with quantitative

evidence.....[which] can be highly synergistic” (Eisenhardt,

1989:537)



The use of a range of methods also enables a process of triangulation, in this technique

multiple methods are used “in the validation process to ensure that the variance

reflected that of the trait and not of the method...In short ‘within-method’ triangulation

essentially involves cross-checking for internal consistency or reliability while ‘between-

method’ triangulation tests the degree of external validity” (Todd, 1979:604). In this

study for example, within-method triangulation is used to confirm that methods of

construction are consistent across site visits whilst between-method triangulation is used

to validate the description of construction processes given in interviews by comparing

them to those observed on site.

2.52.52.52.5 The use of iThe use of iThe use of iThe use of interviewsnterviewsnterviewsnterviews

Interviews constitute a key element of the study since qualitative methods are deemed to

“facilitate study of issues in depth and detail” (Patton cited in Bartlett, 2005:43); clearly

necessary qualities in research leading to the creation of a code of practice. Interviews

were also used to supplement direct test results and site visits since “much of what we

cannot observe for ourselves has been or is being observed by others” (Stake as cited in

Bartlett, 2005:53).

Interviews can be classified as structured, semi-structured and unstructured (Robson,

2002:269). In structured interviews the researcher asks a pre-determined set of

questions whilst in unstructured interviews interviewees are not directed, but are free to

talk about anything (Bartlett, 2005:53); both styles were deemed inappropriate for

researching the first two objectives since though the researcher was looking to address

certain key questions, it was also essential to allow the interviewees to introduce issues

previously unknown to her. Semi-structured interviews were therefore conducted with

engineers, urban planners and architects, as this enables the conversation to be guided

by a list of themes, and yet ensures the interviewer may also seek clarification,

elaboration and enter into a dialogue with the interviewee (May, 2001:121).

Unstructured interviews in the form of informal interviews were considered appropriate to

the third objective; Robson designates informal interviews as times when the researcher

“takes an opportunity that arises to have a (usually short) chat with someone in the

research setting about anything which seems relevant” (Robson, 2002:282). The third

objective, to establish the state of knowledge on rammed earth, was therefore pursued

through site visits combined with informal interviews allowing the researcher to discuss

detailed aspects of the construction process with the traditional craftsmen in context.



For research to be considered valid and the results generalisable it is essential that the

interview sample be representative of the study population; after all “no amount of

analytic sophistication can compensate if the right people were not asked the right

questions in the right way” (Fisher cited in Bartlett, 2005:53). Many researchers

therefore use methods such as random sampling, stratified random sampling or cluster

sampling (Haralambos and Holborn, 2000:994) to ensure the sample reflects the wider

population. However “standard sampling...techniques require the researcher to...have a

sampling frame, a list of all members in the population” (Salganik and Heckathorn,

2004:194). Clearly the key stakeholders in the creation of a code of practice for Bhutan

are difficult to identify let alone produce a sampling frame from, and hence snowball (or

chain-referral) sampling is used. In this method “respondents are selected not from a

sampling frame but from the...network of existing members of the sample. The sampling

process begins when the researchers select a small number of seeds who are the first

people to participate in the study” (Salganik and Heckathorn, 2004:194). Snowball

sampling is also quicker and allows a larger sample size within the tight timescale of the

field visit; hence this method was used to find appropriate interviewees.

2.62.62.62.6 Comparison with literatureComparison with literatureComparison with literatureComparison with literature

“Overall, tying the emergent theory to existing literature enhances the

internal validity [and] generalizability...it is particularly crucial in theory-

building research because the findings often rest on a very limited number

of cases. In this situation, any further corroboration of internal validity or

generalizability is an important improvement.” (Eisenhardt, 1989:545)

The comparison of field work results with the findings from the detailed literature review

hence plays a key role in enhancing the validity of the research. The process of

comparison involved “asking what is this similar to, what does it contradict, and why”

(Eisenhardt, 1989:544) and in doing so furthers the depth of understanding of the

subject and hence improves the quality of the eventual code.



3333 Data collectionData collectionData collectionData collection

Data were collected through a combination of literature reviews, interviews, site visits and

soil testing. This section looks at each method in turn reviewing the work that was

undertaken, the issues that emerged and how they were overcome.

3.13.13.13.1 Initial literature reviewInitial literature reviewInitial literature reviewInitial literature review

Between October and December 2007 an initial literature review was undertaken in order

to discover if there were any existing codes on rammed earth construction and whether

any of them would be appropriate to the needs of the Bhutanese engineering sector. The

review also provided a framework for the fieldwork in clarifying aspects of construction

which would need investigating and highlighting gaps in the literature which should be

addressed.

The review looked at UK building regulations and Eurocodes, as well as published

literature on rammed earth. The key texts examined included:

• BS EN 1996 Eurocode 6 Design of masonry structures

• BS EN 1997 Eurocode 7 Geotechnical design

• Approved Document A, The Building Regulations 2000. 2004 Edition.

• Gernot Minke (2000) “Earth Construction Handbook”

• Julian Keable (1996) “Rammed Earth Structures: a code of practice”

The main difficulty faced was in obtaining standards and literature from Bhutan since

these are not available on the internet and are too large to be sent via email. It was

therefore decided to use the interviews and site visits to obtain further Bhutanese

documentation.

3.23.23.23.2 SemiSemiSemiSemi----structured structured structured structured InterviewsInterviewsInterviewsInterviews

The researcher met with the director of the Department of Urban Development and

Engineering Services (DUDES) on the first day of the field visit to establish key points of

contact. Within the first three working days of the visit meetings were conducted with

representatives from SNV (Netherlands Development Organisation), SPBD (Schools

Planning and Building Division), SQCA (Standards & Quality Control Authority) and Tashi

Dawa Associates (a Thimphu based architectural practice). On return to the capital

further interviews were arranged with the Urban Planning and Structural Engineering



section within DUDES. The interviews hence covered a range of stakeholders from the

private, voluntary and government sector as well as a variety of engineers, architects and

urban planners.

InterviInterviInterviInterview questionsew questionsew questionsew questions

The semi-structured interviews focussed on the first two research objectives: is there a

need for a code and what is required of a code if there is. Before each interview an

interview plan was prepared depending on the nature of the organisation to be visited; for

instance interviews with SPBD and Tashi Dawa Associates focussed more on the current

codes they use and any problems experience in using them whilst the interview with

SQCA discussed how Indian Codes have been adapted for use in Bhutan and the

production of Bhutanese codes. All interviews were also used to find new contacts,

sources of literature and suggestions of relevant sites to visit.

Conducting the interviewsConducting the interviewsConducting the interviewsConducting the interviews

The researcher made certain to explain the research and its objectives at the start of

each interview. During the interviews brief notes were made in a field notebook and

interviews were recorded with the prior permission of interviewees. It was the intention

that all interviews be reviewed within 48 hours however this was rarely achievable for a

number of reasons: firstly the researcher was staying as a guest in the houses of contacts

made on a previous visit and hence it would have been considered as impolite to work all

evening, secondly there was not always an area with sufficient lighting and heating to

work at night. Although all houses had electricity none had more than single electric light

bulbs and sometimes one electric bar heater. The researcher therefore made certain to

record key sites, contacts and titles of necessary literature in the field notebook to ensure

all leads were followed up whilst in Bhutan.

Style of interviewingStyle of interviewingStyle of interviewingStyle of interviewing

Gummesson (cited Bartlett, 2005:56) suggests that pre-understanding is essential in a

study taking an inductive approach and quotes Andersson as stating “personal

experience of the area of study is considered to be a scientific merit” (Gummesson cited

Bartlett, 2005:56). As a young, female, foreign engineer it was of considerable

advantage to the researcher to have prior understanding of Bhutanese culture and

knowledge of the engineering sector in Bhutan. The researcher was therefore able to

dress appropriately in traditional dress (a habit requiring considerable practice) and use



Figure 3:Figure 3:Figure 3:Figure 3: Map of Bhutan showing location of Thimphu and Wangdue (http://maps.google.co.uk/maps)

the correct terms of address in speaking with senior officials. These measures, combined

with a few words of introduction in Dzongkha (although the interviews were all conducted

in English) are considered to have been crucial to the quality of the interviews and the

level of understanding achieved.

The interviews followed the ethical approach advocated by Scheyvens and Storey (2003)

which requires “building mutually beneficial relationships with the people you meet in the

field and...acting in a sensitive and respectful manner”. The Bhutanese are exceptionally

polite and it therefore required concentration and discipline to both ensure the

researcher was not told what it was presumed she wanted to hear, and to push questions

without seeming rude in a culture which is by nature non-confrontational. In addition to

deliberately conforming to Bhutanese etiquette the researcher therefore discussed the

potential of the work and suggested collaboration with key interviewees in the production

of the code.

3.33.33.33.3 Site visits and informal interviewsSite visits and informal interviewsSite visits and informal interviewsSite visits and informal interviews

A total of 11 sites were visited in the areas surrounding Thimphu and Wangdue

Phodrang, these included 5 sites under construction, 3 recently completed and 3

structures of over 100 years old. At the ongoing sites measurements, photos, video

footage and a visual inspection were taken. Drawings were obtained for the buildings

wherever possible and a detailed informal interview with the skilled craftsmen conducted



by means of a translator. During site visits to recently completed and older structures

photos and measurements were taken and where possible interviews conducted with the

occupants to obtain information on the age of the building, maintenance procedures and

its predicted future lifespan and mode of failure.

Data gatheredData gatheredData gatheredData gathered

Through a combination of observation and interviews data was gathered on the materials

used, water content and soil testing procedure as well as current material storage

practices. Earth samples were taken and wherever possible the mud was collected just

before being rammed.

Dimensions of foundations and stonework up to plinth level were obtained as were wall

thicknesses and heights. Measurements of the wooden shuttering were taken and the

ramming process was observed in detail to ascertain the quantity of earth used the level

of compaction and time taken. Particular attention was given to how wall connections

were made and how the walls were reinforced, however this relied heavily on interviews

and the descriptions were sometimes conflicting. The sites visited were at various stages

of completion enabling a better understanding of how the buildings work and in particular

the flooring systems which were viewed at various stages of progression.

Both completed buildings and those still under construction were examined closely for

signs of movement and any evidence of cracking was photographed in detail. The

dimensions and details given in interviews were checked against the actual site

measurements and then crosschecked on further site visits.

Issues of translationIssues of translationIssues of translationIssues of translation

Translation was not required for the semi-structured interviews since all were

professionals fluent in English; informal interviews were conducted with the craftsmen

who rarely had any knowledge of English and hence it was essential to be accompanied

by someone with a reasonable level of Dzongkha and English. In most cases this

translation support could be provided by the site engineer or otherwise contacts made on

the previous visit; it was therefore not considered necessary to find an interpreter.

In some cases this approach did not work; the engineers were not used to acting as

translators and would hence attempt to answer my question themselves or their first



language was not Dzongkha and hence there were communication difficulties between

them and the craftsmen. In other instances however it worked well; particularly where

the site engineer was from a rural background and spoke the local dialect, since in these

cases there was a real rapport between the craftspeople and the site engineer and they

would often volunteer information and elaborate without further questioning.

Investigation approachInvestigation approachInvestigation approachInvestigation approach

There were several public holidays during the field visit and sites were often deserted

preventing both interviews and the collection of ‘ready to be rammed’ mud samples;

some sites were visited three times before the head craftsman could be located and

explain the method in detail.

“Flexibility is controlled opportunism in which researchers take advantage

of the uniqueness of a specific case...to improve resultant theory.”

(Eisenhardt, 1989:539)

Potential opportunities for site visits and interviews often arose at short notice and it was

essential to be flexible both in timing and questioning. Often new construction details or

explanations would emerge that were then included and cross checked on subsequent

sites.

Data collection was facilitated by the relationships formed previously between the

researcher and the engineers in Wangdue Phodrang. The engineers went out of their way

to accompany the researcher on site visits at weekends in appreciation of the tight time

constraints of the field visit as well as discussing the research and suggesting potential

sites and sources of further information. These engineers also made excellent

translators; although their grasp of English was not always good, their understanding of

the motivations of the project and the needs of the research meant they would often

follow up questions themselves and engage in conversation with the craftsmen, only then

relaying the information to the researcher once they themselves were convinced by the

thorough nature of the response.

As with the formal interviews the nature of the research and intended use of the data

were explained at the outset of the interview and consent obtained before using the

dictaphone. Permission was also sought before taking photographs and video footage



and the researcher made a conscious effort to photograph the buildings and not the

people, and also to be seen to be doing so.

3.43.43.43.4 Soil testingSoil testingSoil testingSoil testing

The soil samples were tested to determine their basis characteristics: the natural (as

used) moisture content, the particle size distribution, the liquid and plastic limits and

hence the plasticity index and undrained shear strength (at the liquid limit and natural

moisture content). The tests were performed following procedures given in BS

1377:1975 Methods for Test of Soils for Civil Engineering Purposes.

Only three of six samples were collected at the point of being rammed, however the

moisture content (BS 1377-2.1.1, 1975) of all samples was taken. This was done by

weighing can and the can plus the soil and leaving it in an oven at 105º C for at least 24

hours, after which the dry soil sample is again weighed. The water content can then be

deduced.

Once all the soil had been oven dried it was then prepared for testing using a rubber

pestle and mortar and subsequently sieving the sample through a 425µm filter before

determining the plastic limit (BS 1377-2.3, 1975). Water was added and the sample

formed into a small ball. This was then broken into sixths and each one rolled over a

glass sheet until it crumbled as it reached a diameter of approximately 3mm. The

moisture content of the samples was then taken.

The liquid limit test (BS 1377-2.2.1, 1975) used a cone penetrometer with an 80g

standard cone. A cup is filled with the sample and the cone poised with its tip just

touching the surface. This is released for 5 seconds and the penetration recorded. Five

different moisture contents were tested with each sample; at each moisture content tests

were repeated until three readings were achieved where the penetration was the same to

within 1mm. This test proved to be by far the most variable with tests having to be

repeated up to 15 times to achieve the level of accuracy desired.

The particle size distribution test (BS 1377-2.7.2, 1975) was performed by placing a

sample of soil on a stack of sieves and placing these on a mechanical shaker for a

minimum of 30 minutes. Each sieve was then weighed with and without the soil

accumulated on it. A wet sieving and sedimentation analysis would have yielded more



accurate results given there was a small but significant proportion of fines; however,

given the time constraints of the research, a dry sieving method was used.

The plasticity index (IP) was deduced from the liquid (wL) and plastic limits (wP):

IP = wL - wP (BS 1377-2.4, 1975)

The undrained shear strength (su) of the soil was calculated from the weight of the cone

(W), the cone angle constant (F) and the depth of penetration (d) using the expression:

W = F su d2 (Soga and White, 2007:3)

3.53.53.53.5 Detailed literature reviewDetailed literature reviewDetailed literature reviewDetailed literature review

The field visit to Bhutan produced a wealth of information in the form of current codes of

practice, architectural literature on historic practices and technical drawings of rammed

earth buildings:

• Codes of practice:

- IS 456: 2000 Plain and reinforced concrete COP

- BTS-009-2003 Bhutan Building Code –Section 8 Masonry Structures

- IS 13826:1993 Improving earthquake resistance of low strength masonry

buildings – guidelines

- IS 13827:1993 Improving earthquake resistance of earthen buildings – guidelines

- Standards for timber doors and windows, Standard & Quality Control Division

(N.B. IS = Indian Standards)

• Drawings:

- SPBD community school and staff quarter drawing in rammed earth

- Gup office structural and architectural design drawings in masonry/rammed earth

• Literature:

- Clear Exposition of Bhutanese Architecture. Chang Dorji (2004)

- Improved traditional housing. Department of Works and Housing

- Survey on Historical Monuments in Wangdue Phodrang Dzongkhag. Junko Mukai

(2006)

- Architectural Heritage Journal, July 2006. Division for Conservation of Architectural

Heritage

- An Introduction to Traditional Architecture of Bhutan. Department of Works and

Housing



The codes were used to establish whether rammed earth was covered at all in existing

literature and examine differences in format, coverage and presentation of Bhutanese

and UK codes of practice. The literature and technical drawings were reviewed against

the primary data gathered to check for consistency of method and technique in

Bhutanese practices.

Contemporary academic research and handbooks on rammed earth construction were

also reviewed and compared against Bhutanese practices and the results of soil sample

testing. The key literature reviewed included:

• Jaquin (2008) Analysis of historic rammed earth construction

• Arya (2007) Earthquake disaster reduction: masonry building, design and construction

• Walker et al. (2005) Rammed earth: design and construction guidelines

• Walker & Maniatidis (2003) A review of rammed earth construction

• Gernot Minke (2001) Construction manual for earthquake-resistant houses built of

earth

• Lilley & Robinson (1995) Ultimate strength of rammed earth walls with openings



4444 FindingsFindingsFindingsFindings

The results of the various data collection methods and analysis are drawn together in this

section. Each research question is reviewed in turn and the associated research

presented in order to give a complete and detailed picture of the findings.



4.14.14.14.1 Is there a nIs there a nIs there a nIs there a need?eed?eed?eed?

The first objective was to verify the need for standards on rammed earth construction for

Bhutan. This necessitated two lines of enquiry: firstly, does an appropriate standard

exist, and secondly, would a code facilitate the continued use of rammed earth in Bhutan.

The results of the initial literature review and semi-structured interviews pertaining to

these two questions are summarised below.

4.1.14.1.14.1.14.1.1 Existing standardsExisting standardsExisting standardsExisting standards

The initial literature review demonstrated that, despite there being a wealth of literature

on rammed earth, there are few codes of practice and none of them appropriate to the

needs of the engineering sector in Bhutan. Codes range from the simply presented

descriptions of traditional methods as per Keable’s “Rammed Earth Structures: a code of

practice” (1996) to the descriptions of more modern techniques involving cement

stabilization and mechanical ramming, as laid out in codes from New Zealand and the

United States. These findings were corroborated by the interviews in Bhutan and a more

detailed literature review.

The Standards and Quality Control Authority (SQCA) of Bhutan confirmed that they do not

currently have a code for rammed earth construction, although they were able to provide

the researcher with Indian standards on the earthquake resistance of earthen and low

strength masonry buildings (IS 13827:1993 and IS 13828:1993) which appear to be the

closest the available literature in Bhutan or India comes to a standard for rammed earth

buildings.

The detailed literature review confirmed that there is no national standard for rammed

earth construction in the UK although guidelines were published by Walker, Keable et al.

in 2005. Although there have been several landmark buildings constructed in rammed

earth in the UK “no standard specifically for rammed earth construction was used during

the design of any of the examined projects [11 UK projects including the Eden project,

Dragons Retreat (Devon) and the Stables (Northamptonshire)]. [However] some guidance

was sought from current literature” (Walker and Maniatidis, 2003:81). The design

procedures used in these projects have generally been based on those used for

unreinforced masonry or the rammed earth has been treated as a low strength mass

concrete (Walker and Maniatidis, 2003:82).



Standards are available for Australia, New Zealand, USA (New Mexico), Zimbabwe,

Germany and Spain and “provisions set out in the Australian, New Zealand and New

Mexican codes often reflect the common use of cement stabilisation in these countries”

(Walker and Maniatidis, 2003:2). Although other countries have produced codes on

earthen construction they either do not cover rammed earth, have been withdrawn, or

copies are unavailable (Walker and Maniatidis, 2003:5).

As well as clearly being inappropriate for direct application in Bhutan owing to cultural,

economic and environmental differences, there has also been criticism that existing

guidelines are highly conservative, thereby preventing economically viable construction

especially in seismically active areas.

“Guidelines for modern construction are simplistic with structural design

guidelines being based on those for unreinforced masonry, and materials

specifications being compliance rather than method based. Because of

this lack of understanding, large material safety factors must be used in

structural design, Walker, Keable et al. (2005) recommend that material

safety factors of between 3 and 6 should be used...These factors are

obviously unacceptable for efficient building design....As the use of

rammed earth becomes more widespread there is an increasing need for

rational structural design guidelines.” Jaquin (2008)

4.1.24.1.24.1.24.1.2 Existing needs Existing needs Existing needs Existing needs

All interviews confirmed that a code for rammed earth structures does not exist and that

the lack of a code is acting as a barrier to rammed earth construction.

“We can’t offer mud rammed structures to clients since there is no

code” A design engineer

“They [Thimphu City Corporation] wanted us to make this two-storey

rammed earth building "earthquake safe" by following standards and

codes applied for masonry construction. For instance, they insisted that

we use G.I pipe or steel rods as vertical reinforcement, which I am sure

you aware, is not compatible for carrying out proper ramming”

An architect



Whilst uncertain of the direct impact of a code for rammed earth construction in the

immediate future, most interviewees expressed a desire for more sustainable

construction in Bhutan and hence felt that the code would contribute to this agenda in

the long term.

“We would want our structures to be very efficient, I mean efficient from

every point of view, but I think that might take a little time.” An architect

“I am sure with time, having codes of practice would be very essential to

promote and protect the traditional methods of construction especially the

rammed earth construction.” An architect

Interviewees also highlighted the complexity and uncertainty surrounding the future of

rammed earth in Bhutan. For instance it became clear that whilst the need for a code

exists mostly in urban areas (since there are no regulatory authorities in rural areas) it is

also in these areas that rammed earth construction faces the greatest obstacles. Most

towns in Bhutan are now planned and the plot sizes are often incompatible with

traditional rammed earth buildings.

A key determinant will be the economic viability of rammed earth buildings, however

opinion was divided as to whether it is cheaper or more expensive than other

construction methods.

“Is there a future for rammed earth in Bhutan? In the city I have my

reservations...because the people they may not be able to afford. Firstly

you have to have land, second thing is the space, consumption of big

space, third thing is it is possible but at what cost?” An urban planner

“It’s actually far cheaper using mud and its also much warmer you know,

especially in a place like Thimphu.” An engineer

“In fact what I’m interested in is, I would like to compare how cost effective it is

to do it in the mechanised form and to do it the manual, the customary

practice one. That would be very useful to us.” An urban planner



The slow pace of construction and a diminishing pool of skilled labour were also seen as

disincentives and hence strong interest was expressed in the possible use of mechanical

ramming.

“This technique has lost its popularity because we don’t have the required

man power. If you go by the customary practice it takes a lot of time, just

trying to do it manually. But maybe the mechanical equipment could

facilitate trying to do it in a shorter period of time.” An architect

“Because it’s so rarely used it’s difficult, I think, to find even the workers to

actually build using mud anymore” An engineer

4.1.34.1.34.1.34.1.3 ConcluConcluConcluConclusion sion sion sion –––– is there a need?is there a need?is there a need?is there a need?

It was verified that the existing Bhutan Building Code (BTS-009-2003) does not include

earth structures. Whilst various national codes exist for other countries, they are

invariably inappropriate for direct application in Bhutan owing to cultural, economic and

environmental differences. Many codes have been developed in areas where stabilized

earth is most commonly used and hence not proven to be appropriate to natural

(unstabilized) rammed earth. Owing to a poor understanding of rammed earth behaviour

many national codes are based on standards for masonry construction and are so

cautious, particularly with regards to design in seismic areas, that their adoption would

render rammed earth construction in Bhutan almost unviable.

The interviews demonstrated that there is a need for a code of practice for rammed earth

construction in Bhutan and that such a code would facilitate the continued use of this

method of construction. However many other issues surrounding the viability of rammed

earth buildings arose. Some of these issues could be addressed by a code; for example

the speed of construction could be increased if the code could incorporate the flexibility

to enable both manual and mechanical ramming. Other factors such as the perceived

economic viability certainly need addressing, however this is outside the remit of a code

of practice and hence does not fall within the scope of this research.



4.24.24.24.2 What is needed?What is needed?What is needed?What is needed?

The second objective was to determine what is required of a code of practice in Bhutan.

A detailed literature review compared the current Bhutan Building Code (BTS-009-2003)

with the equivalent Eurocode, as well as examining the coverage of guidelines on

rammed earth, whilst interviews attempted to establish the shortcomings of current

codes and obtain recommendations for improvements.

4.2.14.2.14.2.14.2.1 Existing codesExisting codesExisting codesExisting codes

LeLeLeLevel of detail vel of detail vel of detail vel of detail

A comparison of the masonry structures section of the Bhutan Building Code (BTS-009-

2003) with the equivalent Eurocode (BS EN 1996 Eurocode 6 Design of masonry

structures) revealed significant differences in the level of detail between the two

documents. This was surprising given that, according to several interviewees, the

Bhutanese codes are based on the Indian codes which were in turn taken from British

codes.

Whilst Eurocode 6 covers 152 pages (including annexes), section 8 of the Bhutanese

code is just 23 pages long, although it does have a narrower scope (excluding reinforced

masonry) and makes reference to other documents in certain areas. The Bhutanese

code is also characterised by concise descriptive text and data tables in contrast to the

Eurocode which makes greater use of equations. This is strongly indicative of the level of

detail and style of guidelines required by the Bhutanese engineering sector and

demonstrates the need for a standard which enables the construction of safe, simple

buildings and does not need to extend to the detailed calculations which would permit

more experimental structural design.

FormatFormatFormatFormat

The format of the Bhutanese codes (BTS BTS-009-2003 and the Standards for timber

doors and windows, Standard & Quality Control Division) is clearer and uses a larger font

size than the Indian or European codes. Whilst the codes are increasingly available on

CD there is still much use of photocopying and hence this clearer format is more

appropriate.



The Standards for timber doors and windows (Standard & Quality Control Division) is one

of the few Bhutanese codes based on traditional practices rather than drawn from

external codes. The standards present several “typical illustrations” where window and

door designs are shown which comply with the code; this approach would appear to suit

the needs of the sector. As one of the interviewees stated:

“What the challenge is...people would like to build, but what we make them

do is come with building plans and...they would not have the capacity to do

a building plan. If we had something on our shelves...like something

standard, we could give it to them and they could actually follow those.”

An architect

ContentContentContentContent

The various national guidelines and reviews on rammed earth construction, although they

should not be used as a basis for the code, provide an excellent point of reference by

which to verify that the code developed covers the necessary aspects of design and

construction and enters into a safe but appropriate level of detail.

One of the key concepts in developing a sustainable code is to “codify traditional

practices rather than overrule them” and the research so far has indicated that content

should not extend to detailed structural calculations. Walker and Maniatidis (2003:24)

also give further credence to this proposal:

“Load bearing earth buildings have developed over millennia completely in

the absence of structural design standards or codes. Rules of thumb for

geometric wall proportions developed through the experience of trial and

error have proven sufficient to enable earth building to achieve at least 10

stories high...In many low rise situations rigorous structural design of walls

is not necessary and wall proportions will follow ‘rule of thumb’ guidelines

for maximum slenderness.” Walker and Maniatidis (2003:24)



4.2.24.2.24.2.24.2.2 Perceived problems with current codes Perceived problems with current codes Perceived problems with current codes Perceived problems with current codes

The key problem highlighted with the Indian standards used in Bhutan is that they are

based on the properties of Indian materials and these often do not match the properties

of Bhutanese materials. This will clearly be addressed in the proposed code for rammed

earth construction since it will be based on Bhutanese materials and practices.

Despite the clearer presentation of the existing Bhutanese codes, interviewees

highlighted that Indian codes are sometimes used in preference to the equivalent

Bhutanese code, since the majority of engineers studied in India and hence are more

familiar with the Indian codes. Since the Bhutan Building Code (BTS-009-2003) was only

published in 2003 and the first batch of engineering students from the Royal University of

Bhutan only graduated in 2006, this situation is therefore hardly surprising, and is likely

to change in the near future. However it is worth bearing in mind how the proposed code

of practice would be introduced and the necessary training that would be needed to

ensure its successful adoption

4.2.34.2.34.2.34.2.3 Conclusion Conclusion Conclusion Conclusion –––– whawhawhawhat is needed?t is needed?t is needed?t is needed?

The level of detail required of a code of practice for rammed earth construction, which is

appropriate to the needs of Bhutanese engineers and is acceptable with regards to safety

considerations, was established as being that which is demonstrated in the Bhutan

Building Code (BTS-009-2003). This gives sufficient guidance to design all but the more

structurally experimental buildings and is hence considered adequate. The existing

codes were also found to be an excellent guide as to the format of the proposed code,

especially in their inclusion of ‘typical illustrations’, which are perceived to meet an

existing need for simple, pre-prepared design drawings.

The various national codes and reviews on rammed earth construction, and in particular

Walker and Maniatidis (2003), are taken to be a suitable guide as to the necessary

content of a code of practice on rammed earth construction. The literature review also

gives further support to the argument that it is safe to follow traditional practices (without

detailed structural calculations) by stating that ‘rule of thumb’ guidelines are acceptable

for most low rise buildings.



4.34.34.34.3 What is known?What is known?What is known?What is known?

The final objective was to establish the state of knowledge on rammed earth in Bhutan

and internationally. The following section therefore presents the knowledge of Bhutanese

practices, drawn from informal interviews, site visits, soil testing and Bhutanese

literature, with reference to existing national standards from around the world. This

section cannot be seen as a summary of the existing knowledge on rammed earth

internationally, but that information which is pertinent and comparable to the data

collected in Bhutan.

It is also important to note that this section deals only with material properties, basic

design considerations (layout, number of storeys etc.) and briefly construction practices.

Detailed design is simply not undertaken for rammed earth buildings in Bhutan,

traditional design is replicated with no calculations involved; therefore to discuss the

design of rammed earth construction in detail would simply repeat existing literature with

no new data from Bhutan for comparison. Seismic design principles are considered

throughout the section with respect to the different elements of design, as these

principles must be integral to the proposed code and not an additional check list at the

end.

The format follows the themes and structure of Walker and Maniatidis’ “A review of

rammed earth construction” (2003) rather than following the format of a guideline which

would necessitate a different approach.



Figure Figure Figure Figure 4444: : : : Photos of soil taken at different sites in BPhotos of soil taken at different sites in BPhotos of soil taken at different sites in BPhotos of soil taken at different sites in Bhutanhutanhutanhutan

4.3.14.3.14.3.14.3.1 MaterialsMaterialsMaterialsMaterials

Soil colourSoil colourSoil colourSoil colour

There was a wide variation in the soil colour between sites, reflecting contrasting

mineralogies and states of weathering; colours ranged from sandy yellow, to grey brown

and deep red; although red was clearly perceived to be the ideal colour. Soil was always

used directly from the site; even when red soil was available in the local area it was never

transported to site, despite the yellow site soil being of apparently poorer quality. This

may reflect the cost of transportation and the inaccessibility of the sites as much as a

lack of preference.

This preference for red coloured soils was echoed in the literature review (Walker and

Maniatidis, 2003:6). Lilley and Robinson (1995:278) comment that the soil used for

rammed earth tends to be “rich in compounds of iron. This accounts for the general

reddish appearance of lateritic soil”.

Moisture ContentMoisture ContentMoisture ContentMoisture Content

The moisture content of the 3 samples collected immediately before ramming was found

to be between 18% and 21%. This seems relatively high compared to Lilley and Robinson

(1995:281) who found the optimum moisture content to be approximately 12%.

This disparity prompts two questions: firstly is the result correct and secondly are the

figures comparable. There is a significant probability, given that the soil samples were

transported from site back to England in containers which are not entirely airtight, that

the results are not true to the original moisture content. However if anything the moisture

content is likely to have decreased not increased and therefore this would not explain the

discrepancy. So it is likely that the optimum moisture content is higher for these soils at

around 20%.



“Values of dry density and optimum moisture content for a given soil are dependent on

compactive effort” (Walker and Maniatidis, 2003:12) and it is therefore likely that the

compactive effort achieved by the soil compaction tests (BS 1377-4, 1990) on which

Lilley and Robinson’s figure is based is not equal to the compactive effort achieved on

site in Bhutan, nor is the particle size distribution the same. Lilley and Robinson

(1995:281) also note that “using soils at their optimum moisture contents indicated by

BS 1377 proved difficult, as the soils tended to adhere to the rammers and the

shuttering”, yet this was certainly not the case in the samples which even at 20%

moisture content were not even “sticking to the hand” (Lilley and Robinson’s (1995:280)

description of checking the optimum water content for pisé,). This criterion of ‘damp but

not sticky’ also matches the description given by Bhutanese craftsmen that the soil

should have the consistency of rice.

It is also possible to gauge a rough estimate of the optimum moisture content using field

tests such as the ‘drop test’ advocated by Walker and Maniatidis (2003:12). It is

interesting to note the remarkable similarity between their description of the test and the

test described by craftsmen in Bhutan:

“You have to make to make a ball of this mud, and you slam it onto the

wall and if the whole of the thing falls down it’s not considered good and if

half of the mud falls and half of the mud stays that is considered best.”

A craftsman

A ball of moist soil...is dropped onto a hard flat surface from a height of

approximately 1.5m. When the soil is too dry the ball breaks into many

pieces. When enough water has been added so that the ball breaks into

only a few pieces, the soil is very close to its optimum moisture content. If

the ball remains in one piece then the soil is too wet.

Walker and Maniatidis (2003)

Hence although the calculated moisture content appears higher, the qualitative tests

would indicate a similar moisture content in both cases.



Figure Figure Figure Figure 5555: : : : Particle size distribution of samples from Bhutan overlayed onto the findings of Lilley and Particle size distribution of samples from Bhutan overlayed onto the findings of Lilley and Particle size distribution of samples from Bhutan overlayed onto the findings of Lilley and Particle size distribution of samples from Bhutan overlayed onto the findings of Lilley and Robinson (1995:27Robinson (1995:27Robinson (1995:27Robinson (1995:279999))))

Particle size distributioParticle size distributioParticle size distributioParticle size distributionnnn

The particle size distribution of each of the soil samples taken is shown in Figure 5

overlaid on the results of Lilley and Robinson (1995:279).

The discrepancy between the results from the Bhutanese soil samples and those of Lilley

and Robinson are due to a combination of factors. Firstly the particle size distribution

was found using dry sieving, since the soil contained significant quantities of fines the

wet sieving method should have been used. The findings are therefore likely to

underestimate the quantity of clay and silt since they will have been trapped on the layers

of soil above. Also owing to the small size of sample (150g approx.) large stones were

effectively excluded from the sample and hence the largest sieve used was 2.36mm,

thereby potentially under representing the largest particle sizes.

There is however wide variation in the recommendations for the grading of soils used for

rammed earth and hence researchers usually publish upper and lower limits for each of

the main soil elements (Walker and Maniatidis, 2003:8). Despite the potential

inaccuracy of the results found (due to the method used), they are presented in figure 6

alongside the findings of Maniatidis and Walker’s review of particle size distributions for

comparison.



These graphs demonstrate that the findings lie within the bounds of previous research,

although the levels of sand and gravel are higher (and hence levels of silt and clay are

lower) than usual. This is likely to be, at lease in part, the result of the method used,

however further testing would be required to corroborate this interpretation.

In summary therefore the particle size distribution found in testing does not correlate

exactly with previous research, however results of previous studies would also indicate

that a wide variety of soils can be used. Despite the use of dry sieving, which leads to an

apparently coarser grading than actual, the results also follow the generally accepted rule

that “the soil should have a high sand/gravel content, with some silt and just enough clay

to act as a binder and assist soil compaction” (Keable (1996) cited in Maniatidis and

Walker, 2003:8).

3020

3525

35 3015

0

80

30 030

00 30

30

20

75

70

75

70 80

70 93

Alley, 1948 Houben &

Guillaud,

1994

McHenry,

1984

Norton,

1997

Radonovic,

1996

Shrader,

1981

SAZS

724:2001

TEST DATA

Up

per

pe

rcen

tage

ra

nge

Sand & Gravel

Silt

Clay

25

0

30

10

3020

5 0

50

10

0

15 0

15

7

10

45

65

45

65

70

5070

Alley, 1948 Houben &

Guillaud,

McHenry,

1984

Norton,

1997

Radonovic,

1996

Shrader,

1981

SAZS

724:2001

TEST DATA

Lo

we

r p

erc

en

tage r

an

ge

Sand & Gravel

Silt

Clay

Figure Figure Figure Figure 6666: : : : Test results from Bhutan presented against suggested upper and lower particle size Test results from Bhutan presented against suggested upper and lower particle size Test results from Bhutan presented against suggested upper and lower particle size Test results from Bhutan presented against suggested upper and lower particle size distributions from Manitidis and Walker (2003:8)distributions from Manitidis and Walker (2003:8)distributions from Manitidis and Walker (2003:8)distributions from Manitidis and Walker (2003:8)



Figure Figure Figure Figure 7777: : : : Plastic limit of soilPlastic limit of soilPlastic limit of soilPlastic limit of soil samples from Bhutan with Houben & Guillaud’s recommended and samples from Bhutan with Houben & Guillaud’s recommended and samples from Bhutan with Houben & Guillaud’s recommended and samples from Bhutan with Houben & Guillaud’s recommended and preferred ranges indicated.preferred ranges indicated.preferred ranges indicated.preferred ranges indicated.

Figure Figure Figure Figure 8888: : : : Liquid limit of soil samples from Bhutan with Houben & Guillaud’s recommended and Liquid limit of soil samples from Bhutan with Houben & Guillaud’s recommended and Liquid limit of soil samples from Bhutan with Houben & Guillaud’s recommended and Liquid limit of soil samples from Bhutan with Houben & Guillaud’s recommended and preferred ranges indicated.preferred ranges indicated.preferred ranges indicated.preferred ranges indicated.

Plastic limitPlastic limitPlastic limitPlastic limit

The plastic limit for all samples fell between 14% and 28% with all but one sample lying

between 20% and 28% (see figure 7). Several results are therefore slightly higher than

recommended by Houben and Guillaud (cited Walker and Maniatidis, 2003:12) who

propose the plastic limit lie between 10% and 25% (12%-22% preferred).

Liquid limitLiquid limitLiquid limitLiquid limit

The liquid limits of samples lay within Houben & Guillaud’s (cited Walker and Maniatidis,

2003:12) recommended range of 25-50%. All but one sample had a liquid limit of

between 34% and 37%, almost within Houben & Guillaud’s preferred range of 30%-35%.



PlPlPlPlasticity indexasticity indexasticity indexasticity index

The plasticity index ranged from 8% to 23%. Alley (cited Walker and Maniatidis, 2003:12)

proposed a plasticity index of 6%, however clearly Houben & Guillaud’s recommended

plastic and liquid limits would lead to a significantly higher value.

Conclusion of materialsConclusion of materialsConclusion of materialsConclusion of materials

The results of the soil testing indicate that the soil selection of Bhutanese craftsmen

corresponds quite closely to the recommendations of the literature reviewed with regards

to the liquid and plastic limits, although the plastic limit is often slightly higher than

advised. The moisture content is significantly higher than recommended. The proportion

of sand and gravel also appears high; however this may largely be due to the method of

dry sieving and hence needs verifying through further testing.

Judging by qualitative measures and the high quality of rammed earth buildings in

Bhutan, it would appear that despite the afore mentioned discrepancies, the soil

selection of Bhutanese craftsmen appears to be effective. It is also noted that given the

different methods of compaction used in Bhutan and those prescribed in the various

national codes, different gradings and moisture contents may be required.

It is also important to note that, according to Walker and Maniatidis (2003:23), “standard

soil characterisation tests...are not reliable to establish the suitability of a soil for rammed

earth. Further testing for mechanical strength and weathering resistance should be

conducted prior to any soil selection...Test performance criteria should be agreed and

specified at the design stage.” This would clearly be difficult in Bhutan and therefore the

implications of choosing a soil purely based on characterisation tests (or the traditional

Bhutanese variation) must be carefully considered in the development of a code.



Figure 9: Typical Bhutanese house with timber frame ecra Figure 9: Typical Bhutanese house with timber frame ecra Figure 9: Typical Bhutanese house with timber frame ecra Figure 9: Typical Bhutanese house with timber frame ecra walls comprising half of each side wall and the front wall at walls comprising half of each side wall and the front wall at walls comprising half of each side wall and the front wall at walls comprising half of each side wall and the front wall at

first floor level. Very few openings in earth walls.first floor level. Very few openings in earth walls.first floor level. Very few openings in earth walls.first floor level. Very few openings in earth walls.

FigureFigureFigureFigure 10: Ruins of rammed earth 10: Ruins of rammed earth 10: Ruins of rammed earth 10: Ruins of rammed earth houses showing how the houses showing how the houses showing how the houses showing how the walls only walls only walls only walls only extend to roof level at the back and extend to roof level at the back and extend to roof level at the back and extend to roof level at the back and

half of each side.half of each side.half of each side.half of each side.

4.3.24.3.24.3.24.3.2 DDDDesignesignesignesign

Architectural design and orientationArchitectural design and orientationArchitectural design and orientationArchitectural design and orientation

The traditional architecture of Bhutan is well documented and hence it may seem

unnecessary to discuss it here. However the code must not just aim to facilitate the

construction of rammed earth buildings, but sustainable buildings also, and hence it is

important bring the sustainable traditions of Bhutanese architecture into the code;

especially given the absence of sustainability criteria in Bhutanese regulations currently.

Bhutanese buildings demonstrate contemporary sustainability principles in their use of

orientation to reduce heat losses and maximise passive solar gain. For instance in

Bhutanese villages “houses and trees are arranged in such a way as to provide each

other with maximum wind shelter” (DoWHR, 1993:188). It is also interesting to note the

use of thermal mass and wind sheltering to create ‘outdoor hot-zones’ both between

buildings in a cluster (DoWHR, 1993:227), and also around the building by means of a

2m high boundary-type wall (DoWHR, 1993:205). Individual buildings generally follow a

typical layout:

“Firstly there is a wall of rammed mud which runs along the back. This wall

generally faces north. Here one finds few, if any, openings...[On the front]

one finds the largest openings. To allow maximum light to enter, the most

prominent rooms are located [here]” (DoWHR, 1993:195)



Figure 11: A four storey house near Thimphu. Figure 11: A four storey house near Thimphu. Figure 11: A four storey house near Thimphu. Figure 11: A four storey house near Thimphu. Occupants said the building had so far lasted 6 Occupants said the building had so far lasted 6 Occupants said the building had so far lasted 6 Occupants said the building had so far lasted 6

generations.generations.generations.generations.

Rammed earth is used on all four sides of all but the top floor; here the front wall and half

of each side wall consist of a timber frame structure with a fill in of plastered bamboo

weaving (known in Bhutan as an ‘ekra wall’), somewhat similar to the English wattle and

daub walls. This type of walling allows greater structural freedom and hence enables

large south facing windows, a key element of passive solar design in climates where

demand for winter heating exceeds that for summer cooling (Walker and Maniatidis,

2003:34). Bhutanese houses often incorporate outdoor landings which “serve as an

outdoor space used during the cold winter months when sunshine hours are plenty and

the outdoor temperature of the sun is considerably higher than that of indoors” (DoWHR,

1993:203).

“A long experience with earthquakes and tremors has made the Bhutanese people

careful” (DoWHR, 1993:201) and hence traditional architecture incorporates many

features characteristic of good seismic design. Houses in Bhutan are invariably

symmetric in plan with symmetric openings, an important precautionary measure in

seismic design (Arya, 2007:101). House plans are also generally square or rectangular,

as advocated by Minke (2001:9).

The major discrepancy between Bhutanese

practice and the recommendations with

regards to seismic design for rammed earth

buildings is the number of storeys. Arya

(2007:101) recommends that the height of

earth buildings should be restricted to one

storey only whilst the Indian Standards (IS

13827- 10.1.1, 1993) advise that in zone 5

(which Bhutan is in) buildings should be

restricted to one storey and important

buildings should not be constructed at all.

Despite these warnings the majority of earth

buildings in Bhutan are two or three storeys

high with a substantial number of taller

buildings. Many of these having survived a

sizeable earthquake in the early 1980s.



Figure 12: Photograph showing masonry Figure 12: Photograph showing masonry Figure 12: Photograph showing masonry Figure 12: Photograph showing masonry footing with mud mortar and footing with mud mortar and footing with mud mortar and footing with mud mortar and stone plinth stone plinth stone plinth stone plinth

protectionprotectionprotectionprotection

FoundationsFoundationsFoundationsFoundations

Traditionally the foundations in Bhutan were always

strip footings made from rubble masonry and mud

mortar, although cement mortar is now often used.

Some craftsmen insisted that if cement mortar was

used, a layer of plastic sheeting (to act as a damp

proof course) should be placed in between the top

of the stonework and the mud, however this was

not a universal practice. According to Walker et al.

(2005:61) the key function of footings at the base

of the wall is to protect the earth wall from

moisture ingress, hence although any simple mass

footing can be used (concrete, masonry, cement-

stabilised rammed earth), a continuous damp-

proofing barrier must be provided. However Minke

(2001:34) argues that horizontal damp-proof courses interrupt the necessary bond

between the plinth and the walls, hence preventing the transfer of shear forces (with

regards to seismic design). In addition to a rough plinth surface he argues that there

should be joints between the plinth and wall every 30-50cm. This is not a traditional

practice in Bhutan nor is it mentioned in any other literature.

The design of foundations for lightly loaded low rise rammed earth buildings can follow

rule of thumb guidelines (Walker and Maniatidis, 2003:65). The dimensions of

foundations measured on site visits and obtained through interviews with the skilled

craftsmen were remarkably consistent and are summarized in Table 1. They have also

been checked against, and found to be consistent with, the dimensions found in

traditional architecture (DoWHR, 1993:191).

Table 1: General guidelines for foundaTable 1: General guidelines for foundaTable 1: General guidelines for foundaTable 1: General guidelines for foundation dimensions in Bhutantion dimensions in Bhutantion dimensions in Bhutantion dimensions in Bhutan –––– Imperial units are given since in Imperial units are given since in Imperial units are given since in Imperial units are given since in practicepracticepracticepractice

the craftsmen invariably gave the measurements in feet and inches.the craftsmen invariably gave the measurements in feet and inches.the craftsmen invariably gave the measurements in feet and inches.the craftsmen invariably gave the measurements in feet and inches.

No. of storeys Depth of foundation Width of foundation Height of plinth upstand

1-2 1.2m (4ft) 0.9m (3ft)

0.6m - 0.9m (2 - 3ft) 3 1.8m (6ft)

1.05m (3.5ft)

4 1.2m (4ft)



Figure 1Figure 1Figure 1Figure 14444: : : : The classic tapered frontage of a 3 The classic tapered frontage of a 3 The classic tapered frontage of a 3 The classic tapered frontage of a 3 storey Bhutanese housestorey Bhutanese housestorey Bhutanese housestorey Bhutanese house

The dimensions of Bhutanese foundations were

all found to be larger than recommended in

various codes (Walker and Maniatidis,

2003:65) where foundation depth and width

never exceed 400mm, however these values

assume reinforced concrete footings. Good

drainage is essential in protecting rammed

earth walls and Bhutanese practice on this

aspect matched the guidance given by various

national codes.

WallsWallsWallsWalls

The minimum wall thickness found in Bhutan was 50cm, apparently in this case the

craftsmen had been given a design where the walls were only 30cm thick and had feared

collapse and hence increased the thickness. Generally the minimum found was 60cm

(2ft) and greater if the building was more than two storeys. This is greater than even the

Zimbabwean Code (generally the more conservative of the various national codes) which

recommends a minimum wall thickness of 300mm (cited in Walker and Maniatidis,

2003:27).

The room dimensions are generally prescribed by the length of available timber and

hence, given their considerable thickness, the wall slenderness is always considerably

less than the maximum dictated by the New Zealand Standard for engineering design of

earth buildings (cited in Walker and Maniatidis, 2003:28).

It is standard practice in Bhutan to taper walls of

buildings greater than 2 storeys and hence wall

thickness at the bottom of large buildings can

reach over 1m. Although the craftsmen explain

the need for tapering as being to prevent bulging

and enhance the aesthetic, Arya (2007:101)

notes that tapering walls provide better stability

against lateral forces and hence are highly

advantageous in seismic areas.

Figure 13: Plinth protection provided by sloping Figure 13: Plinth protection provided by sloping Figure 13: Plinth protection provided by sloping Figure 13: Plinth protection provided by sloping

paving leading to drainage channelpaving leading to drainage channelpaving leading to drainage channelpaving leading to drainage channel



Figure Figure Figure Figure 15: Walls are well connected at 15: Walls are well connected at 15: Walls are well connected at 15: Walls are well connected at corners by overlapping alternate corners by overlapping alternate corners by overlapping alternate corners by overlapping alternate

‘bl‘bl‘bl‘blocks’ ocks’ ocks’ ocks’

It is also common practice to place bundles of bamboo, or 3’’x4’’ planks, horizontally in

the middle of each ‘block’ of earth (one block is 2’-3’ height of earth rammed in a day and

is dictated by the height of the shuttering). This is done at corners and towards the

middle of a wall if there are no windows or doors, where the lintels would otherwise fulfil

a similar function. These would appear to fulfil the role of ‘bond beams’ as described by

Arya (2007:102) and hence improve the seismic performance of the building.

Although Bhutanese buildings do not incorporate ring beams or vertical reinforcement,

both of which are generally considered critical in seismic design, they achieve effective

seismic performance be means of ‘stabilization through mass’. Minke states that:

“Rammed earth walls 60 to 100cm thick...can withstand horizontal seismic

shocks...old age [buildings] withstood all earthquakes, whereas newly

constructed houses next to them collapsed, even when they were built with

bricks and a concrete ring beam.” Minke (2001:15)

The buildings conform to Minke’s first principle for

designing an earthquake-resistant structure, which

is that “walls and roof are well interconnected and

so rigid that no deformation occurs in the

earthquake” (Minke, 2001:12) and hence is not of

the type which requires a ring beam. Walls are well

connected by interlocking ‘blocks’ (the 2’-3’ layers

of earth which can be rammed in a day) at the

corners producing a ‘finger joint’.

The relatively small floor plan of Bhutanese houses

means that internal walls are rarely load bearing;

they are therefore usually made of ekra (wattle and

daub) or mud brick if higher levels of sound

insulation are required, such as in a school.



Figure Figure Figure Figure 16: Recently completed rammed earth 16: Recently completed rammed earth 16: Recently completed rammed earth 16: Recently completed rammed earth building showing roof truss with CGI sheeting building showing roof truss with CGI sheeting building showing roof truss with CGI sheeting building showing roof truss with CGI sheeting

above rammed earth flat roofabove rammed earth flat roofabove rammed earth flat roofabove rammed earth flat roof

OpeningsOpeningsOpeningsOpenings

Windows and doors in rammed earth walls are traditionally kept to a minimum in

Bhutanese buildings with the timber and ekra frontage on the upper floors providing the

light and ventilation required. They therefore invariably comply with both load bearing

and seismic design guidance which describes the maximum total length of openings,

distance to corners etc. They do not however comply with Minke’s recommendations

regarding emergency exits; doors open inwards and there is no form of emergency exit at

ground floor level (i.e. there is only one entrance and no windows large enough to serve

as an exit).

Roof and floorsRoof and floorsRoof and floorsRoof and floors

All floors of Bhutanese rammed earth buildings are multilayered. Primary wooden beams

support secondary wooden beams onto which planks are laid, these are then covered in

three inches of lightly rammed earth and covered with a layer of floor boards which are

then left exposed.

The same method is used for the roof,

though without the uppermost layer of floor

boards. Above this flat mud roof is an

additional sloping roof on a timber frame,

traditionally clad with shinglip (or wooden

shingles) and more recently corrugated

metal sheeting. This method of

construction runs contrary to the primary

seismic design principle of using a light

weight roof, however the roof is without

gables which is advised (Minke, 2001:37).

Conclusion of designConclusion of designConclusion of designConclusion of design

Overall, Bhutanese building designs are heavily conservative with regards to basic

structural design principles as found in various national standards. However although

they generally exhibit good seismic performance and integrate many principles of seismic

design, they do not conform to several key recommendations on earth-quake resistant

design: in particular the number of storeys, heavy roofs, lack of vertical reinforcement or

ring beam.



4.3.34.3.34.3.34.3.3 ConsConsConsConstruction truction truction truction

Whilst the construction of Bhutanese rammed earth buildings has been closely observed

and recorded by the researcher, it is unnecessary to document it in any detail here.

Although clearly manual and mechanical ramming require different strengths of formwork

etc, the construction processes observed in Bhutan do not pose any contradictions to the

existing literature and are generally more conservative with regards to compaction.

Therefore the proposed code of practice on rammed earth construction could certainly

follow traditional Bhutanese construction techniques without contravening any of the

various national codes reviewed.



5555 ConclusionsConclusionsConclusionsConclusions and Recommendationsand Recommendationsand Recommendationsand Recommendations

The aim of the project was to carry out the research necessary to the development of an

appropriate standard for rammed earth construction in Bhutan. This aim was broken

down into 3 key research questions and associated objectives which have formed the

basis and the structure of this report. The findings of each research strand have been

summarised within each section; it is hence the role of this section not to repeat the

conclusions already drawn, but to link these back to the overall aim, by explaining how

the conclusions translate into recommendations for a code of practice, as well as

highlighting areas where further research is required. Several issues emerged that

straddle multiple research questions and are hence discussed at the end of the section,

along with the overall findings.

Is there a need?Is there a need?Is there a need?Is there a need?

Verify whether there is a need in Bhutan for standards on rammed earth

This project was based on the premise that there was a need for standards in order to

facilitate and encourage the continued use of rammed earth in Bhutan, particularly in

urban areas. This need was verified through a literature review and interviews, these

demonstrated that:

• A lack of standards is acting as a barrier to rammed earth construction in urban areas

of Bhutan

• A code of practice on rammed earth construction would therefore facilitate and

encourage the continued use of this construction method

• The Bhutan Building Code (BTS-009-2003) does not cover rammed earth construction

• Whilst other countries have developed various national codes of practice and

guidelines, none of these are appropriate to the needs of the Bhutanese engineering

sector in terms of format, content and level of detail

It is therefore recommended that a Bhutanese code of practice on rammed earth

construction be developed. It is recognised however, that this recommendation assumes

that rammed earth construction is economically sustainable and will continued to be

used in Bhutan in the future. It would be unwise to invest in the development of a code if

the many other barriers to its continuation are not addressed; it is therefore

recommended that research be conducted into the sustainability of rammed earth

construction in Bhutan.



What is needed?What is needed?What is needed?What is needed?

Determine what is required of a code of practice in Bhutan

Since the need for a code of practice on rammed earth construction has been

established it is therefore essential to consider what the requirements of such a code

are, and how it can be made appropriate to the needs of the Bhutanese engineering

sector. A review of existing Bhutanese codes, Eurocodes, various national standards on

rammed earth construction and interviews showed that a code of practice for Bhutan

should:

• Provide sufficient level of detail to enable the construction of safe, simple buildings

but should not extend to detailed structural calculations

• Have a clear format (even when photocopied) and should include template design

drawings

• Cover all aspects of materials, design and construction

• Be based on the properties of Bhutanese materials

On the basis of these findings it is recommended that in the development of a code of

practice for rammed earth construction in Bhutan:

• The Bhutan Building Code (BTS-009-2003) be used as a benchmark with regards to

the level of detail required

• The Standards for Timber Doors & Windows (SQCD 2002) be used as a guideline on

the format, since it is considered highly appropriate in this respect

• National standards on rammed earth construction from other countries inform the

code with regards to the various aspects of material selection, design and

construction which should be covered

• Bhutanese materials and traditional practices be the basis of the content of the code



What is known?What is known?What is known?What is known?

Establish the state of knowledge on rammed earth in Bhutan and internationally

An appropriate standard was defined as being one which codifies traditional practices

rather than overruling them and yet maintains the breadth and technical rigour as codes

used elsewhere in the world. In order to develop such a code it was therefore essential to

gain an in depth understanding of Bhutanese practices and how these compare to

various national standards on rammed earth from different countries.

Large quantities of data on rammed earth construction and the design of traditional

housing in Bhutan were collected through a combination of site visits, informal interviews,

soil testing and literature reviews. Whilst all of this data will feed into the development of

a code of practice, only those aspects where there was significant correlation or

discrepancy between Bhutanese practices (and areas where data was directly

comparable – such as the soil tests) have been described within the findings section.

These are summarised below as they indicate areas where traditional practices may have

to be questioned, further research undertaken or where elements of traditional design

that would not normally be included in a code of practice are considered to be relevant

and hence should be incorporated.

Materials

• Despite some differences between the soil used in Bhutan and that recommended in

the various national standards, it would appear that the soil selection of Bhutanese

craftsmen generates high quality buildings.

• Further research should be conducted into the properties of the finished rammed

earth walls in Bhutan as these would be helpful, although not essential, in the basic

structural design.

• According to the literature reviewed standard soil characterisation tests are not seen

as reliable in establishing the suitability of a soil for rammed earth construction,

further testing of mechanical strength and weathering resistance are advised prior to

soil selection. However given the apparently consistent high quality of Bhutanese

buildings and the difficulties of performing such tests in Bhutan, serious consideration

must be given to how soil specifications will be stipulated in the code.



Design

• Bhutanese buildings satisfy all the basic structural design rules as found in various

national standards on rammed earth construction. Hence traditional Bhutanese rules

of thumb for building design may be safely followed with regards to basic structural

stability.

• Traditional rammed earth buildings in Bhutan exhibit many principles of good seismic

and sustainable building design and these should be incorporated into the code

• Most Bhutanese rammed earth buildings do not follow certain key recommendations

on earth-quake resistant design. Bhutanese traditional design should therefore not

followed blindly, however to insist on the incorporation of all conventional earth-quake

resistant design features would also be ill-advised since it would interfere with

construction practices and hence could potentially reduce the building’s capability to

withstand earthquakes. Further expert advice should therefore be sought on the

issue of seismic design.

Construction

• Construction processes observed in Bhutan do not pose any contradictions to the

existing literature and are generally more conservative with regards to compaction.

Therefore the proposed code of practice on rammed earth construction could follow

traditional Bhutanese construction techniques without contravening any of the

various national codes reviewed.



Overall findingsOverall findingsOverall findingsOverall findings

There is a clear need for a code of practice on rammed earth construction in Bhutan and

the requirements of such a code have been clearly identified.

A code of practice can be written on the basis of traditional Bhutanese design and

construction practices without contravening recommendations made by the various

national codes on rammed earth construction reviewed. This is with the exception of

considerations relating to seismic design; further expert advice should be sought in order

to find a safe balance between traditional practice and conventional earthquake resistant

features.

By incorporating the flexibility to enable mechanical ramming and reduce wall

thicknesses, the code could address some of the disincentives to constructing rammed

earth buildings, such as the slow pace of construction, a diminishing pool of skilled labour

and the large area required; however in doing so it will stray from traditional practices.

International norms must be more strictly adhered to if this approach is taken, since the

wealth of traditional knowledge that currently provides the crucial safety factor in

Bhutanese rammed earth buildings will become redundant.



6666 AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements

I would like to thank the Minister of MoWHS, the Director of DUDES and David Stiedl for

supporting my visit to Bhutan for a second time. I am grateful to all those I interviewed

and the various friends who stepped in as chauffeurs and translators for making my first

taste of research such a fascinating and rewarding one. I am indebted to Tsering

Choden, Yasoda, Khima and Bhima Luital for their incredible hospitality over the three

weeks I stayed with them and for teaching me to cook ema datze, kir and dahl. I would

also like to thank the whole of the Wangdue Phodrang Engineering Section; in particular

Yeshi Tenzin for his patience in driving me endlessly around the district in search of mud

houses and Sangay Pemo, Choki Wangmo and Karma Choden for dressing me in a kira

until I eventually learnt to do it for myself.

I really appreciate having had the opportunity to work in the Centre for Sustainable

Development this year, it is wonderful to work surrounded by such an inspiring crowd.

Lastly I would like to thank Professor Peter Guthrie whose pertinent questions forced me

to rediscover the fun of thinking.



7777 ReferencesReferencesReferencesReferences

Approved Document A, The Building Regulations 2000. 2004 Edition. Office of the Deputy Prime Minister Arya (2007) Earthquake disaster reduction: masonry building, design and construction, Knowledge World Publishers. Bartlett (2005) Understanding the Implementation of Sustainability Principles in UK Educational Building Projects Bhutan Building Code BTS-009-2003– Structural Design: Section 8 Masonry Structures Bryman, A. (2001) Social Research Methods, Oxford University Press, Oxford BS EN 1996 Eurocode 6 Design of masonry structures BS EN 1997 Eurocode 7 Geotechnical design BS EN 1998 Eurocode 8 Design of structures for earthquake resistance BS 1377:1975 Methods for Test of Soils for Civil Engineering Purposes BSI British Standards (2007) www.bsi-global.com/en/Standards-and-Publications/About-standards/What-is-a-standard/, accessed November 2007 Chang Dorji (2004) Clear Exposition of Bhutanese Architecture. Constructing Excellence in the Built Environment (May 2006) Rethinking standards in construction: can standards support industry performance improvement Department of Works, Housing and Roads, Bhutan (DoWHR) (1993) An Introduction to Traditional Architecture of Bhutan. Department of Works, Housing and Roads, Bhutan (DoWHR) Improved traditional housing (illustrated hand book). Division for Conservation of Architectural Heritage (July 2006) Architectural Heritage Journal Eisenhardt, K. M. (1989) Building Theories from Case Study Research Academy of Management Review, 14141414 (4),,,, pp.532-550. 3.Francis, A.J. and Mansell, D.S. (1988) Appropriate engineering technology for developing countries, Research Publications Pty. Ltd. Haralambos and Holborn (2000) Sociology themes and perspectives 5th edition, Collins. Indian Standard 456: 2000 Plain and reinforced concrete code of practice



Indian Standard 13826:1993 Improving earthquake resistance of low strength masonry buildings – guidelines Indian Standard IS 13827:1993 Improving earthquake resistance of earthen buildings – guidelines Jaquin, P. (2008) Analysis of historic rammed earth construction Junko Mukai (2006) Survey on Historical Monuments in Wangdue Phodrang Dzongkhag Lilley, D. M. and Robinson, J. (1995) Ultimate Strength of Rammed Earth Walls with Openings. Proceedings of the Institution of Civil Engineers-Structures and Buildings, 110110110110 (3), pp. 278-287. Keable, J. (1996) Rammed Earth Structures: a code of practice, Intermediate Technology Publications May, T. (2001) Social Research: Issues, Methods and Process, Open University Press. Minke, G. (2001) Construction manual for earthquake-resistant houses built of earth, GATE – Building Advisory Service and Information Network Minke, G. (2000) Earth Construction Handbook: The building material earth in modern architecture. WIT Press. Robson, C. (2002) Real World Research, Blackwell, Oxford. Salganik, M.J. and Heckathorn, D.D. (2004) Sampling and Estimation in Hidden Populations Using Respondent-Driven Sampling, Sociological Methodology, 34343434, pp. 193-239. Schumacher, E.F. (1977) Caring for real, New World News, 17 September 1977. Standard & Quality Control Division, Bhutan (2002) Standards for timber doors and windows Soga, K. and White, D. (2007) Soil Classification Tests: The Atterberg Limits, Engineering Tripos Part 2A: Paper 3D1, Laboratory Exercise Todd, D. J. (1979) Mixing Qualitative and Quantitative Methods: Triangulation in Action Administrative Science Quarterly, 24242424 (4), pp. 602-611. Walker, P., Keable, R., Martin, J. and Maniatidis, V. (2005) Rammed Earth: Design and Construction Guidelines. BRE Bookshop. Walker, P. and Maniatidis, V. (2003) A Review of Rammed Earth Construction – Dti Partners in Innovation Project ‘Developing Rammed Earth for UK Housing’. Natural Building Technology Group, Department of Architecture & Civil Engineering, University of Bath.



8888 Appendix AAppendix AAppendix AAppendix A –––– Risk assessment retrospectiveRisk assessment retrospectiveRisk assessment retrospectiveRisk assessment retrospective

The initial risk assessment submitted in October was followed up by a subsequent risk

assessment in April before conducting soil testing in the Geotechnical Laboratory.

In retrospect the risk assessment should have included the risk of dust in the air and the

need to wear a dust mask when performing some of the tests. However the testing was

completed safely.

Documents

A sustainability approach to standards for rammed earth construction in Bhutan