Safe and Affordable Urban Housing in Bangladesh Promoting better building techniques in Dinajpur Town â€“ a Case Study
Safe and Affordable Housing in Bangladesh Disseminating better building techniques Team: John Arnold Azit Roy Marianne Keating Sam Stephens Shareq Rauf Chowdhury Poramol Roy Pulin Roy With thanks to: Apu Chandra Roy Imran Morshed Khazi Ishita Alam Abonee Ishita Mouri Rahman Khaled A Sheikh Mahmuda Alam Orko Jahanjir Rubiyat-ur-Rahman Showeb Al-Kadri Tushar Kanti Roy Uzzal Roy With support from: Simple Action For the Environment (SAFE) safebangladesh.wordpress.com Housing and Hazards www.housingandhazards.org Australian High Commission British Womenâ€™s Association (Dhaka) Urban Partnerships for Poverty Reduction (UPPR) 2
Contents Contents .......................................................................................................................................................... 3 Executive Summary ......................................................................................................................................... 4 Introduction .................................................................................................................................................... 5 The place and people ...................................................................................................................................... 8 Participatory Design and Construction â€“ the process ................................................................................... 13 12.
Recommended construction improvements .................................................................................... 16
Adaptable house designs for Jorgen Babur Mart ......................................................................................... 23 Costs .............................................................................................................................................................. 26 Key Issues, Chellenges and Next Steps ......................................................................................................... 27 List of Appendices ......................................................................................................................................... 30
Executive Summary This report details a pilot project to design and build 10 safe and affordable homes in a slum area in Dinajpur town, in the north east of Bangladesh. A multidisciplinary team of architects, engineers and a local NGO (SAFE) worked with a slum community to identify and demonstrate improved construction techniques using traditional materials. The principle behind these improvements is that they remain affordable but produce a house which is more liveable, safer and ultimately lasts longer â€“ saving households money in the longer term and leaving them less vulnerable to disaster. The aim of this project was to demonstrate these improvements in such a way that they would be replicated by the local community after the project was finished. To this end a participatory process involving local families was used during the design and construction so that improvements would be appropriate and understood by all. Although it is too early to see if techniques have been fully accepted and replicated, the participatory process was successful and a strong relationship formed between the NGO and the community. This helped the construction work go smoothly with few delays. The 10 demonstration houses and input from the NGO were almost fully subsidized, but with labour and in some cases financial contributions from the households. Even at this early stage, it is clear that households are taking pride in their new homes, carrying out regular maintenance and contributing to a local savings scheme dedicated for future maintenance. Different contexts (i.e land values, environmental conditions, resources available) will require different housing solutions, and any significant investment in housing will require some degree of secure land tenure. This project focuses on low-cost low-rise, typically self-built housing that would be appropriate for households with limited resources, or/and a limited security of tenure (eg.10 year lease or â€˜right to stayâ€™). Supporting households in self-built housing offers an opportunity to rapidly increase the supply of safe lowincome housing in Bangladesh. This project demonstrates an approach that supports this mode of construction to produce safer and more economical houses in the longer term. Key to the project is not just the technical elements but its participatory nature, designed to transfer skills and understanding to the local community so that the ideas might be replicated in the future.
Introduction Urbanisation - an opportunity Urban populations in Bangladesh have seen huge growth since the country’s independence in 1971. Approximately 40 million (25% of the population) people now live in towns or cities compared with 8% at independence1. Dhaka, the capital, has approximately 16 million inhabitants and is the 9th largest and one of the fastest growing cities in the world. Much of this urban migration can be attributed to economic opportunities. Urban populations now contribute to over 70% of the national GDP. Managed well, towns and cities can be drivers of economic growth, and can be seen as Bangladesh’s best opportunity of reducing poverty2. Unfortunately Bangladesh’s towns and cities are ill equipped to manage this growth, which places huge demands on space and infrastructure. Scarcity of land, poor transport, lack of planning and lack of affordable credit often makes it difficult for people, especially lower income groups, to find suitable housing convenient to their place of work. The result has been a huge increase in the numbers of slums – areas of housing characterised by lack of secure land tenure, lack of formal services like water or electricity and cramped, insanitary conditions. Project scope Different contexts will require different housing solutions: a site in Dhaka where land values are high may preclude anything but multi-storey development in order to keep unit costs down; a household owning land maybe willing to invest in more permanent housing than a household with informal rights; a household who are not saving, or planning for the future beyond the current year are unlikely to be ready to invest in their own housing at all, preferring perhaps to rent. This project focuses on low-cost low-rise, typically self-built housing that would be appropriate for households with limited resources, or/and a limited security of tenure (eg.10 year lease or ‘right to stay’).
Islam, Nazrul and Salma A. Shafi (2008) “A Proposal for a Housing Development Programme in Dhaka City,” Centre for Urban Studies (CUS), Dhaka. 2 World Bank (2007) ”Bangladesh: Strategy for Sustained Growth”. Bangladesh Development Series, Paper no. 18. Dhaka, Bangladesh. 1
Aerial view of Jorgen Babur Mart
Self-built housing – an opportunity Self built housing is the prevalent mode of construction among low income groups in Bangladesh. Self-built, in this context, means that the homeowner is closely involved with every aspect of construction. For a household with limited resources it offers the most economical approach: improvements can be carried out incrementally as resources become available or as need requires (eg. adding an extra room for a newly married son). Self-construction is not usually guided by any safety standards, but by word of mouth and informal knowledge, and can often lead to hap-hazard buildings which are vulnerable to hazards such as earthquakes or storms. However self-construction, if properly supported, presents an opportunity to increase the supply of affordable homes which are safer and longer-lasting. The issues of securing tenure and access to finance –of which both have a huge affect on the type of housing options available are beyond the scope of this project. Communicating improved self-built construction There are many issues and constraints which will influence a project aimed at improving self-built construction practices. Important factors that should be considered include:
`Opportunity cost of households time. Time is money, especially in slums. Households may not be able to afford time to participate and so those households who spent significant time attending workshops during the planning stages were compensated. Other workshops and events were held on Fridays when residents were not working.
Security of tenure. If there is a threat of eviction then households are unlikely to want to invest money in their home. The families involved in this project held ‘right to stay’ documentation from the local government, and had been settled for many years without threat of eviction.
No extra cash. Resources are scarce, and when they are available households have to balance many competing demands for their use. To invest in housing, households must be thinking and planning several years ahead and saving accordingly.
Benefits of improved housing may seem marginal. In the face of many (more immediate) risks, the threat of a risk such as a storm, and its potential impact on health, livelihood etc may seem too far off to justify importance.
Further to these, any improvements in construction are more likely to be replicated if they are: 6
A workshop with local community to explain the techniques being used in the construction of the new houses.
Desirable. One of the main challenges to this project is that traditional materials, such as bamboo and mud are often associated with poverty/low status.
Simple and affordable
Available locally. includes not just materials but also skilled labour within local communities.
Their benefits are fully understood. For example, if a household is going to pay extra money for treated bamboo they must be aware of the payback period.
To address these issues fully – to understand what people have and what they want, to share ideas and to have them understood - a participatory approach which builds trust between all parties provides many advantages. The participatory process we have followed in this project is outlined in later chapter ‘Participatory Design and Construction – the process’. An important component of the process is that learning is transferred to the local community and builders through doing practical work – building demonstration houses or through practical workshops, considered much more effective and appropriate means of teaching in this context.3
‘Learning by doing’ –Ian Davis, (1996), Shelter After Disaster
An initial meeting between SAFE and community members
The place and people Jorgen Babu Mart is an area situated approximately 2km from the centre of Dinajpur town. Originally the land belonged to Jorgen Babu, a Hindu land owner who emigrated to India during the partition of India and the former East Pakistan. The government is now the de-facto owner of the land. Households do not possess individual title deeds but many do have â€˜right to stayâ€™ documents from the local government. The area has been established for many years and with threat of eviction low many households have invested in pucca (permanent) housing. This project has focussed on one section of Jorgen Babur Mart inhabited by approximately 50 families. The land they occupy was once waterlogged and uninhabitable but was reclaimed approximately 7 years ago by the NGO CARE. Many of the families were previously squatting on land belonging to Bangladesh Railways. The people who make up this area of Jorgen Babur Mart are both Hindu and Muslim. They have come from different parts of the NW of Banlgadesh and many for economic reasons. They are involved in occupations ranging from TV-repair men to day labourers to rickshaw pullers and earn between Tk.100-250 per day. Although some women work outside the area, most stay at home but generate extra income through home-based activities such as poppadom rolling or handicraft production. In a survey of 30 of these families over half had existing micro-loans and a similar number also held small savings with 1 of 3 organisations. Detailed interviews of 10 households are given in appendix G.
Nurul Islam Nurul lives in a small single room house with his wife Hasina and his two youngest children Hasan and Sumi. They moved to Jorgen Babur Mart in 2001 with help from NGO CARE after being evicted from there previous house in a nearby slum. He did not start life out in Dinajpur, but was born in Dhan Ghora, a village near Rangpur about 60km to the west. He lost both parents within the first year of his life – his father died before he was 2 months old and his mother suffered from mental illness and disappeared. He was taken in by his grandmother who looked after him throughout his childhood. In 1974 when Nurul was about 11, Bangladesh suffered severe famines under the new government formed after independence with Pakistan. Nurul came to Dinajpur with his grandmother in search of work and food. They settled in a slum area called Sheshshahir Moor Bosti where he remained until the slum was cleared in 2001. During that time Nurul marries Hasina, they have 3 children and he has a variety of jobs including cart puller and lorry driver’s assistant. It is during this last job that Nurul suffers a severe accident which affects his back and leaves him unable to walk for 3 years – relying on help from his family to move him around. With no savings, he is unable to get any professional medical help and Hasina starts working full time as a day labourer to compensate. With the help of pain killers and a bamboo brace, he slowly regains strength and starts to walk and work again. With his back partially recovered things are better. He now works as a rickshaw peddler earning Tk150-200 per day, though can only manage about 3 days a week due to back pain. His wife works as a house builder, often 7 days a week when there is work. They save Tk10 a week as part of an NGO savings scheme but currently only have Tk400. Their daughter, Sumi, age 9, attends a Nurul and family outside their home in Jorgen nearby BRAC school in the afternoons. When she grows up she Babur Mart wants to be a teacher. Hasan, 7, doesn’t like going to school and often truants despite being taken there by his mother before she starts work. He is falling way behind and his mother is worried that he will drop out completely. She tells us with an exasperated look how he recently sold his books in exchange for some peanuts. Their house is not the best – small at 9ft x 18ft, in poor condition and located next to the communal toilets. Despite that he is proud and happy to have his own land without the threat of eviction. Owing to the poor condition of his home, Nurul’s home was chosen by the community to be the first demonstration house to be built.
Shahin Islam in his bedroom and study he shares with his brother. There are no windows.
Physical environment Housing in this area is linear with plots laid out on two sides of a single narrow lane. On either side of the lane behind the plots run two surface drains. Communal toilets have been built in the centre of the area. This infrastructure was provided by INGO CARE when the land was reclaimed, but is in poor condition with no structures set up to take responsibility for maintenance. Plot sizes vary between 8ft x 18ft up to 30ft x 18ft and are often divided up into several small rooms to cater for 3 generations of the same family. The houses area simply constructed with a bamboo frame, lean-to roofs of Corrugated Iron (CI) sheet and wall materials of either CI sheet or bamboo mat. Several houses have private tube wells and 2 houses have private latrines constructed in partnership with the Urban Partnerships for Poverty Reduction project. A formal electric connection exists to the area with many households connected. A few trees exist within the plots though there is little greenery and no households grow any vegetables.
Plan of existing house for 8 family members A typical cross-section of existing housing â€“ see plan overleaf
Plan of existing house for 8 family members
Existing settlement pattern. Households involved in construction are highlighted.
Existing Problems and Opportunities
All houses lack adequate ventilation with very few windows or gaps to allow natural ventilation. As a consequence many households use electric lights and fans during the daytime.
The CI sheet used for roofs and walls provides very poor insulation and rooms are stiflingly hot during the day and cold during the winter.
The drainage of the whole area is poor and all houses are regularly flooded during the monsoon season. This is compounded by the poor maintenance of the existing surface drains.
Most households cook on small portable clay stoves, and burn locally purchased wood. Without adequate ventilation many women prefer to cook outside, however when it is raining the resulting smoke inside the houses is a problem.
With up to 3 generations sharing a small plot, space is a real issue. A husband, wife and children will often sharing a room as small as 11’ x 9’. As a consequence and owing to the heat many women who roll and dry poppadoms prefer to do so in the congested and dirty lane outside.
Drains running behind houses are not regularly maintained and flood intermittently during the rainy season.
The bamboo used in construction rots quickly in the ground and is subject to attack from insects above. Posts need to be replaced every 1-2 years but are often left leaving houses weak.
With many families living in the area for a long time there is a strong sense of community
Drains and toilets exist, but just needs to be properly maintained.
Strong winds do occasionally affect the region however they are of a much smaller scale that the cyclones affecting the south of Bangladesh. The area is not exposed.
Participatory Design and Construction â€“ the process The design process has been undertaken in conjunction with the community and local builders. This is important to ensure that our design matches the requirements of the households, and is specific to Jorgen Babur Mart â€“ using available materials and addressing the issues specific to this place. The process is designed to build trust between all parties and to ensure that all households and builders understand the improved techniques we are promoting. The process we have undertaken for this project is as follows: 1. Initial meetings. Primarily with the Community Based Organisation and then the whole community to explain the project. 2. Study. This involved short survey of approx. 30 households within community including identifying existing house types and construction techniques; identification of local builders, available materials, and; mapping of the community. 3. Selection of 10 households. Households were chosen by the community based on need, and verified by our own surveys. The chosen households were announced by the CBO at a community meeting. 4. Dream house workshop. A 1 day workshop attended by the 10 households, CBO members and facilitated by the SAFE team and architecture students from BRAC University. Each household was given materials and asked to build their dream house â€“ the only constraints being that it must be on their existing land. This helped us to understand what people wanted in terms of their space requirements. Ideas which came out of this workshop included an area for growing vegetables, extra flexible space - for guests, for children to play and for income generating activities like drying poppadoms. To get this extra space many households built 2 storey houses. At the end of this workshop the group decided on who would build the first house. 5. Initial design. Appropriate improvements were selected by the design team and design options worked up. A tentative budget of US$500 for construction was developed. 6. Design workshop. A 3 day workshop attended by local house builders, households, CBO members and facilitated again by the SAFE team and architecture students from BRAC University. 13
Participants present their dream houses
The first part of the workshop was used to show people improved building techniques as practiced by SAFE. This included a practical demonstration of a low cost method of treating bamboo. A local song team attended and sang songs which reinforced these messages. The second part focussed on developing initial designs. Working in mixed groups â€“ builders, household members and architecture students, models were built of two different designs which incorporated the improvements discussed on the first day of the workshop. Next the groups worked out the costs of each house. These came out higher than the tentative budget set previously and the groups were encouraged to find ways of reducing costs, whilst maintaining the agreed improvements. These included recycling materials from their old houses, reducing optional extras like expensive window and door frames, households adding their own money and/or undertaking more of the labour themselves. At the end of the workshop a timeframe for construction of the first house was agreed. See Appendix H for a detailed programme from this workshop. The workshop programme is detailed in Appendix H. 7. Detailed design and costing. Two generic designs were developed and costed by SAFE and BRAC architecture students. The full costing which has been developed further during construction phase, is given in Appendix C. 8. Construction of first demonstration house. Although the costs for the basic house were met be met by the project, responsibilities were agreed between SAFE and participants: households were be responsible for dismantling houses, keeping site clean, providing 2 people daily for labour during construction and carrying materials to site â€“ this was recorded clearly in an informal written contract between SAFE and the household. The first house provided an opportunity to review the design and construction as people at full-scale. 9. Regular workshops. As the construction progressed a further 6 practical workshops were carried out. These workshops further reinforced understanding about the house design and construction techniques. To try and spread the word, different participants were invited â€“ other households from the same area, and builders and other community leaders from surrounding slums. 10. Construction of remaining 9 houses. Following a review of the first house, and with improvements taken on board for the remaining houses, a timeframe for the construction of the remaining houses was agreed and construction commenced. Houses were built incrementally 14
BRAC architecture students, builders and household work on the design during the workshops
with up to 3 (connected row) houses at a time. Construction of 1 house with approx 4no. builders took on average 3-4 weeks. As the construction continued, leaders emerged from the building team and more responsibility was placed on the builders and households with SAFE taking a more ‘hands off’ role.Local play or ‘jattra’. An evenings’ programme of events was organised to further promote the project within the immediate community. This including performances from a local song team, and a short play acted by the local builders and participating households. The play and many of the songs reinforce the safer building techniques of the project. 11. Promotional leaflets. Instructional leaflets were produced in Bangla giving further information on cross-bracing techniques and distributed amongst residents of Jorgen Babur Mart. See appendix C. 12. Savings group for maintenance. Although these houses may require less maintenance that traditional techniques, regular maintenance is still essential if the houses are to remain strong and safe in the longer term. The 10 households were encouraged to start a savings group. A small weekly amount is deposited with the savings groups leader and this money could be used when repairs were needed.
Local builders promote the project in a jattra (local play)
Local community members learn about cross-bracing and cement stabilisation of earth during practical workshops
Recommended construction improvements Rather than produce a single design to be indiscriminately copied SAFE recommends a range of design improvement options. These are modest technological changes that will increase the performance of existing housing types by strengthening or improving parts which are particularly weak or vulnerable to the local climate. This will save households money in the long run through increased longevity of materials while making them less vulnerable to hazards such as floods or strong winds. These improved building techniques use available materials and are low cost – scaled to the actual costs that low income households invest in housing. We aim for these improvements to increase total costs of building by only 20%. Techniques are based on practical experience from SAFE’s team and existing best practice on the subject4,5,6. Techniques are context specific but would be applicable in many locations throughout Bangladesh. This approach is adaptable. It acknowledges that no two houses are the same – different people have different aspirations, family sizes, occupations and budgets, and as such will need different houses. 1.
Plinth Stabilisation and preparation. Flood water and rain causes cracking and damage to mud plinths. They require regular maintenance and obtaining this mud from local sources can be problematic. When flood water enters the house floors become muddy and create a poor environment. Stabilising the plinth with a small amount of cement has been found to substantially increase its resistance to dampness and erosion by water, preventing the need for regular maintenance. The entire plinth does not need to be stabilised - only a capping layer of approximately 3 – 6in. Prior to this the plinth should be constructed in compacted layers of regular soil. The plinth should have a minimum slope of 1% for drainage. Cement stabilisation is suitable for soil that has a low clay content. Soil with more than 10% clay content may need to be modified by the addition of sand.
Iftekar, K.A. (2005) Handbook on Design and Construction of Housing for Flood-Prone Rural Areas of Bangladesh, ADPC. Available at www.sheltercentre.org 5 Mallick, F.H. et al.(2008) Improved design and construction of rural housing in Noakhali, IUCN. 6 Chisholm, M.P. (1979) A study of the provision of rural housing in Bangladesh. BArch thesis, vols. I & II. University of Newcastle upon Tyne, UK. 4
Plinth capping with cement stabilised mud – taken from Handbook on Design and Construction of Housing for Flood-Prone Rural Areas
2. ‘Kaatla’ or concrete stump When in contact with the ground bamboo posts rot quickly in as little as 1 year. The use of a concrete stump ensures that the bamboo is raised above the ground level. A good connection between the kaatla and the bamboo is required. For the two storey buildings constructed in this project we recommend a slightly larger kaatla than shown adjacent in order to resist uplift from the wind – see drwg MCL100-005 in Appendix B. 3. Bamboo treatment Untreated bamboo will be attacked by insects and a life-span of approximately 4-6 years can be expected. Treated bamboo should last 15–20 years if it is kept protected from the elements. A cost effective way of treating bamboo, undertaken previously by SAFE, uses a solution of borax, boric acid and water. This solution penetrates the bamboo easily, reducing the level of sap in the bamboo and making it less likely to be damaged by insects. The method used here is known as the Vertical Soak Diffusion technique7: the bamboo is stacked vertically and the solution is poured inside from the top end (prior to this a hole was made in each diaphragm using a long metal rod, hammered into one end; the last diaphragm being left so that water
Above: Kaatla or concrete posts; left: bamboo treatment using vertical soak method 7
Vertical Soak Diffusion for Bamboo Preservation, Environmental Bamboo Foundation, 2003. www.bamboocentral.org
Bamboo treatment with borax/boric acid solution
would be contained within the bamboo). This method increases the cost of the bamboo by approx. 20%. 4. Cross bracing Cross bracing and plan bracing are essential to increase stability in high winds. Currently very few houses use cross bracing. The location of the cross bracing and the connection between to the frame is important to ensure that it functions correctly. As part of this project, field testing was undertaken to determine the strength of these bolted connections, and simple guidelines in English and Bangla produced to ensure correct installation of cross bracing. These can be found in Appendices D & E. The position of cross bracing is also detailed in the design drawings in Appendix B.
> 50mm/ 2â€?
Cross bracing fixing detail. Fixing no less than 50mm from end of culm with a node between the fixing and the end. Refer to Appendix E.
5. Stronger joints Existing practice is to use jute string (natural and degrades quickly) or nails (which can cause culm to split). It is essential that good connections are made between the foundations, walls and roof to ensure that the structure is not damaged during strong winds. Bolted connections were used where stronger connections were required - between wall posts and foundations and first floor joists and for cross bracing. Bamboo nails and nylon string were used in other locations.
6. Wall materials Different wall materials depending on the location:
Wattle and daub type. Mud stabilised with cement is applied to a bamboo lattice approx 1-2” thick. This type of wall requires regular maintenance if exposed to rain and so is best suited to walls protected by a roof overhang. The mud provides better insulation than materials such as CI sheets or bamboo mat.
CI sheet/bamboo mat. CI sheet is placed on the lower part of the wall where it is more likely to get wet and with bamboo matting above. This reduces costs while maintaining the longevity of the wall. Cement stabilised ‘wattle and daub’ wall
7. Stronger roof structure Improvements to the existing construction were used which will make the roof structure more resistant to strong winds:
Roof form pitched with a slope between 30-40 degrees where possible.
Overhangs should be 2ft 6in to provide protection from rain whilst resisting uplift by wind.
Strong connections should be made between the roof structure and the walls using nylon string and bamboo nails as shown in (5).
CI sheets should be fixed at every 3 corrugations with twisted roofing nails and at every 2 corrugations along edges.
CI sheet should be of minimum gauge 0.35mm. Thinner CI sheet is widely used but is less cost effective due to its shorter life span.
Extra fixings at the bottom of the sheet
CI sheet at the bottom of the wall where subject to splash back from rain improves longevity
8. Ventilation, insulation and lighting
Adequately sized, lockable windows were included. Windows were constructed with timber frames and bamboo slats. Refer to Appendix A for more pictures of the completed houses.
Bamboo louvers at the top of walls were used to increase the amount of airflow, however these were omitted in later houses due to cold drafts in the winter months.
A trial ‘solar bottle bulb’ was installed in the roof of one house as well as clear plastic roof sheet. A report on the installation and costs of these is given in Appendix F.
Flat ceilings of bamboo mat were installed underneath the roof, to provide a degree of protection from the heat transmitted through the roof sheets.
For the two storey houses the first floor was made using a bamboo joists and slats, with a 1” layer of cement stabilised mud. This mud layers provides a degree of insulation to the room below. Louvers at the top of the wall for improved ventilation
Solar light bottle bulb
Windows improve ventilation and lighting
9. Kitchen garden and planting The growing of vegetables offers an opportunity for households to save money and eat a more nutritious diet, while improving their immediate environment. Vegetation and planting were encouraged through:
Promotion at workshops, where pictures of ‘good practice’ from other slums were shown. The houses were designed with space at front and back to allow for planting. Frames were provided to encourage climbing plants. A competition was held where prizes were given to households who had done the best planting.
10. Improved cook stove GIZ’s (German govt.s development organisation) improved cook stove or ‘bondo chula’ is available locally. When maintained and used properly it will reduce fuel consumption by up to 40% from a traditional stove. It would be installed with an exhaust flue to remove smoke from the kitchen area. Where budget permited, households installed improved cook stoves.
Adaptable house designs for Jorgen Babur Mart Although all the houses are slightly different, owing to households’ needs and space constraints, they were based on 2 generic designs for a single storey and two storey (ground+1) building. Photos of the houses are given in appendix A. Architectural and structural design drawings for these houses are found in appendix B. Structural calculations were undertaken for the two storey house to ensure the house would resist strong winds. Calculations were made using the Indian Design Code IS85:1987 and a design wind speed of 139km/h. Using this wind force and the dimensions of the house, forces acting on the crossbracing were discerned. Practical testing of the bamboo cross-bracing connections was undertaken to ascertain their ability to withstand the expected forces and is shown in Appendix D. A 100kPa allowable soil bearing pressure was used to size foundations to resist forces arising from gravity loading as well as overturning due to wind. By inspection, wind-force design will be sufficient to account for expected earthquake forces. The features of the design which offer significant improvement from existing practice are as follows: Single storey design (refer to Appendices A & B for further photos and architectural and structural sketches) The design features of this house, other than the improvement mentioned above are as follows:
One storey house as per the space requirements
2 ft. recess from the narrow lane has been provided at the front to allow space for growing vegetables and plants
Space has been allowed for the later provision of a tube well and latrine.
Kitchen at the rear allows easy access to drain and proposed tube well.
Retractable door at the front to allow overnight storage of rickshaw.
Louvers to allow improved ventilation and access for drying popadoms on roof.
Wide door allows overnight storage of rickshaw
Two storey row house (refer to Appendices A & B for photos and architectural and structural sketches) The design features of this house, other than the improvements mentioned above are as follows:
Two storey house so that family has extra space
Veranda on 1st floor overlooking street to provides utility space for activities such as drying clothes and rolling popodoms, whilst allowing users to socially interact with neighbours.
Shared wall between adjoining properties, which saved costs. A written agreement between the neighbours to clarify responsibilities for maintenance was drawn up.
2 ft. Set back from the lane has been provided at the front to allow space for growing vegetables and plants. Space also provided at the rear for the same.
Space has been allowed for the later provision of a latrine towards the rear.
Kitchen at the rear allows easy access to drain and proposed tube well.
Pitched roof provided more strength in high winds.
Discussing the design of the first house with the household and builders
Costs A detailed cost breakdown for each house type is given in appendix C. The costs for materials and labour (excluding the costs for design, workshops and other costs for SAFE to manage etc) are as follows: Single storey house (Nurul’s) Total floor area – 256 sqft Total cost – Tk 41,728 ($ 521) Total cost per sqft – 160Tk/sqft ($2)
Two-storey house (Rubi) Total floor area – 284 sqft Total cost – Tk 39,597 ($495) Total cost per sqft – 139Tk/sqft ($1.74)
The relative difference between the two designs can be explained by the significant cost of the metal roofing sheets. The 2-storey house has a smaller footprint than the single storey house and therefore required less roofing sheets.
Key Issues, Chellenges and Next Steps Take up by other households At the time of writing only 5 months had passed since the final house was completed. This is too early to assess whether improved techniques are being copied in the wider community and a further assessment will be required at the end of the following construction season (June 2013). One barrier to this will be the social stigma attached with traditional materials such as bamboo and mud - associated with poverty and low social status. The aspiration of most households is to own a brick or â€˜pukkaâ€™ house. It is hoped that because the houses look distinctive, that they combine new ideas with traditional materials, and ultimately because they are significantly cheaper than brick houses that this may be overcome. Another barrier is that the total cost of the houses still far exceeds what many people could afford through their own savings. Many of the improvements used in this project can be implemented incrementally, reducing the need to make a large one off investment. However it is important to note that savings programmes and access to affordable credit for housing construction are key to enable poor households to improve their housing. Linking the provision of credit with improved self-build construction has been trialled with some degree of success in Delhi by Micro Home Solutions8 Participatory design and construction At this stage it may be too early to tell whether the participatory process has successfully passed on information to the wider community. However the participatory approach helped to make the construction phase run smoothly. Working in such a small area with poor access and shared with many other families it was important to have the full cooperation and trust of the community to ensure there were no delays. Also even at this early stage, households are taking pride in their new homes, carrying out regular maintenance and contributing to a local savings scheme dedicated for future maintenance. During the construction it was planned that more control would be handed over to local builders and households, especially with regard to finance. Although households were involved to some degree in the purchasing of materials, most of the financial planning and accounting was done by the SAFE. In Micro Home Solutions (2011), Self Construction: enabling safe and affordable housing, available at www.microhomesolutions.org 8
reality for this to happen the money needs to be in the hands of the household – either in the form of their own funds, or perhaps given by the NGO at staggered intervals during construction (eg. After successful completion of the foundations, money is given for the walls). Scaling up In this project the costs the houses were fully subsidized. It is likely that subsidies will always be required to demonstrate and promote new techniques such as these, but it is hoped that households could meet more of the costs as SAFE has done in its rural programmes. Again, the presence of savings and affordable credit amongst the community would be important here. Below is an outline framework for the participatory approach used here (detailed more in the previous chapter ‘Participatory Design and Construction – the process’). With the training of community level building specialists at its core, it is a model which could be replicated at scale across many communities in Bangladesh, given some security of tenure and access to savings or affordable credit.
Familiarisation with locality and it’s problems;
Develop potential design improvement options;
Documentation of settlement patterns, existing house typologies, costs of construction and impact of disaster on households.
Build relationship with community;
Focus group discussions; 2.
Design and Implementation
To decide on design improvement options appropriate to place;
Design workshop involving participating households, local builders; Focus group discussions;
To agree improvement options with local builders and households;
Build models with the community
To demonstrate design improvements;
Construction of one demonstration house using design improvement options.
To train local builders and households in these new techniques;
Mini-workshops to train builders and households about improved construction techniques. Ensure participation by the household including decision making and contribution of labour and available resources; Review and make changes to design improvements where required.
To make local people independent from external consultants;
Construction and/or strengthening of 5-10 houses, replicating activities from step (3);
SAFE team to take a more â€˜hands-offâ€™ role with responsibility for construction quality, costs and programme transferred to builders and households. Undertake more workshops to disseminate within wider community and other poor communities in local area. Promotional activities: produce leaflets & other media such as local play; provide limited no. of small subsidies for using new techniques â€“ giving more exposure within the community. Link other poor communities in the town. Involve them in workshops, try and create links between community leaders.
List of Appendices Appendix A - p31 A selection of photos of the houses during and after construction Appendix B - p36 Key plan of location of houses and house owners Sketch of cross section of Rubi & Shabitribalaâ€™s house looking east. Sketch of typical single storey house Structural drawings for typical 2-storey house Appendix C - p48 Cost budget for single storey house Breakdown of costs for 2-storey house (Rubi and Fahimaâ€™s) Appendix D - p52 Field tests of bolted bamboo connections Appendix E - p68 Simple guidelines for cross-bracing - leaflet Appendix F - p73 Solar light bulb installation report Appendix G - p79 Location key plan of households & interview of household Appendix H - p89 3-day design workshop programme
Appendix A A selection of photos of the houses during and after construction
Appendix B Key plan of location of houses and house owners Sketch of cross section of Rubi & Shabitribalaâ€™s house looking east. Sketch of typical single storey house Structural drawings for typical 2-storey house
Appendix C Cost budget for single storey house Breakdown of costs for 2-storey house (Rubi and Fahimaâ€™s)
Cost budget breakdown for typical single storey house Notes These figures are budget costs only and based on outline design for single‐storey house shown in Appendix B Labour is assumed at 200Tk/day Household is assumed to provide 2 labourers throughout construction Cost does not include extra cost of SAFE supervision, training or transport costs Labour costs given are minimum ‐ the first 2‐3 houses will require approx. 50% more labour as builders are learning new techniques and design CI sheet = Corrugated Iron Sheet Assume recycled Corrugated Iron (CI) sheet 270 sqft Total floor area Improved cook stove not included in price
Quantity 1 Plinth Plinth volume = 1' x 266 Assume compaction ration of Total volume of earth required Volume of 1 trolley Total no. trolleys required, say Cost of 1 trolley of earth Total cost of earth for plinth Labour for carrying and placing earth
256 0.75 341 90 4 500
Material Labour Total cost (tk) Cost (Tk) Cost (Tk)
cuft cuft cuft Tk 2000 400
Sub‐total 2 Stabilisation of capping layer Assume average thickness 3" Volume of cement reqired Cost of cement @ 375Tk/bag Labour
bags 563 900
Sub‐total 3 Concrete stump ('kaatla') No. required Total cost @ 140Tk/stump (incl 2no. 3/8" screws per kaatla) Labour for making kaatla Labour for fixing in ground
14 1960 200 200
Sub‐total 4 Posts Average length required 8', assume 1 culm gives 2 posts Cost of 1no. 3‐4" dia culm (Borobas) Total cost Labour to fix to kaatla & posts
2360 15 8 220
no. culms Tk 1760 200
Sub‐total 5 Cross bracing & wall plates 5no. walls cross braced, approx length 11.5 ft Bamboo req. @ 2no. piece per culm, 220Tk ea 6" nails for cross bracing joints Bamboo for wall plates, approx length 16ft, maklabas @ 160Tk/ea Labour Nylon string for all bamboo nailed joints, 2kg
3 40 6
no. pc. no.
660 75 640 800 175
Sub‐total 6 Roof frame Use 'maklabas' bamboo dia 2‐3", spacing @ 2ft 3in c/c Bamboo required, assume 22ft usable length per culm Labour to fix rafters Purlins, use 'goranime' timber, 2"x1" @ 420Tk/cuft, total length 250ft Labour to fix purlins Nails to fix purlins to rafters Side roof, length 10ft, make using bamboo and recycled CI sheet Bamboo required
1470 400 220
Sub‐total 7 Roof sheet Use 0.26mm thick CI sheet @ 4800Tk per 72ft x2.5ft (1no. 'ban') Length of roof spans = 8ft + 7ft + 7ft Width 18ft Total length Ridge plate, 18ft length Roofing nails Labour to fix roof sheets
22 8 176
ft sheets ft
11733 560 500 400
Cost budget breakdown for typical single storey house
Sub‐total 8 Walls External walls to have 3no. rails to support windows and wall cladding Bamboo req, use 1‐2"dia 'maklabas' bamboo @ 160/Tk ea, assume 18ft usable length
Louver, made with 8no. bamboo strip or 'bata', total length required = (2x16') + (2x10') Bamboo req, assume that 1no. bamboo gives 8no. strips 18ft long. Labour to fix louvers
Lower part of external wall use recycled CI sheet Labour to fix rails and CI sheet
Assume recycled CI sheet will be used on walls where possible, assume area of CI sheet walls fixed with horizontal bamboo strip at 2ft c/c, length of strip required Bamboo req, assume that 1no. bamboo gives 8no. strips 18ft long. Tying wire Labour, assume 2 men can fix 240sqft in 1 day
150 200 1.4
Remaining area of internal and external walls to be constructed with bamboo mat ('bera') Use bamboo strips or 'bata' at 1 ft c/c on both sides of mat in a grid pattern Bamboo req, assume that 1no. bamboo gives 8no. strips 18ft long. Cost of bamboo mat, @ 150Tk for 4'6" x 6' sheet Labour to fix walls, assume 2 men can make and fix 100 sqft in one day
280 1220 9 11
sqft ft no.
160 400 250
sqft ft no. no.
1440 1650 1120
Sub‐total 9 Borax treatment @ 1Tk per 1ft bamboo, based on vertical soak diffussion method, reusing borax solution 4 times. Total culms (25') Total length to be treated Assume labour undertaken by household
Sub‐total 10 Doors and windows ‐ basic option Recycle 1no. door, make 1 new. Use mango wood @450 Tk/cuft Labour Windows ‐ use bamboo and recycled CI sheet Bamboo required Labour
Hinges and nails etc
Total costs Cost per square foot
Extras costs to improve the finish of the house ‐ make it stand out Paint & brushes for lower CI sheet panels Extra bamboo for trims and finishes Windows and doors ‐ extra costs for expensive option Extra bamboo for bamboo strip cladding Window and door timber, use mango wood @ 450Tk/cuft Locking chains for doors Hinges and nails etc Labour for making and fitting
960 765 160 330
Ladder for access for drying popodoms and access to roof Bamboo required Labour
Bamboo frame for roof climbing plants Bamboo required Labour
Plants Labour to contruct flower bed
480 400 500 400
Total cost including extra costs Cost per square foot
Appendix C - Breakdown of costs 2 storey house (Rubi and Fahima’s)
No detailed bill of quantities has been produced but a typical cross section of this house given in Appendix B – “Sketch of cross section of Rubi & Shabitribala’s house looking east” (house on the right hand side of page) Costs include labour and materials only and do not include overheads and management costs of SAFE. The floor area of each house is 12’ x 17’ downstairs and 12’ x 15’ upstairs. Total floor area = 384 sqft. Total cost per house = Tk 39,575 per house Total cost per sqft = 39,575/384 = 103 Tk/sqft or $1.25 sqft
Note: Costs below are for 2 houses Job 100 101 102 103 104 105 106 107
Rubi and Fahima's House Katla Treated Bamboo (131 pc) Floor CI Sheet Bamboo Matt Wood/Purlin Bolts/Others
BDT 4,379 BDT 22,308 BDT 1,800 BDT 12,318 BDT 1,450 BDT 1,389 BDT 4,980
Materials Transport Total Monthly Expenditure Total Expenditure
Appendix D Field tests of bolted bamboo connections
Improvised field testing of bolted bamboo connections for use in bracing of informal housing. 15 June 2012 Samuel G Stephens BE (Hons) Structural Engineer SAFE (NGO) Bangladesh
The following report and all its recommendations are to be used for informative purposes only. The Author and SAFE (NGO) Bangladesh take no responsibility for damage to property or life resulting from this report being used for anything other than its intended purpose. The following does not purport to be a scientific or definitive document. Field testing was carried out in an improvised manner to provide at least some Engineering basis for the improvement of low-cost housing construction in Bangladesh.
Abstract Improvised field testing was carried out to ascertain a reasonable strength value for bolted bamboo connections used in the cross-bracing of informal housing. A single connection strength of 3.9kN was determined (which includes a 0.60 safety factor for variations in materials and construction) provided that the following requirements are met; • All cross-bracing members must terminate in a node (a 'node' is a naturally occurring, regular spaced thickening present in bamboo). • The end distance between the bolt and the end of the cross-bracing member must not be less than 2" (51mm) • The minimum wall thickness of bamboo to be used as a cross-bracing member is to be 3/4" (19mm) • The minimum outer diameter of bamboo to be used as a cross-bracing member is to be 2.5" (63mm) Further testing is required to confirm these results.
Contents Abstract ................................................................................................................................................... 1 1.
Introduction .................................................................................................................................... 3
Materials and methods ................................................................................................................... 3
As-built cross-bracing survey .......................................................................................................... 5
Results ............................................................................................................................................. 5
Findings ........................................................................................................................................... 7 a.
Initial ........................................................................................................................................... 7
Load Capacity ............................................................................................................................. 7
Discussion........................................................................................................................................ 7 a.
Suitability of Load Capacity ......................................................................................................... 7
Guidelines for construction......................................................................................................... 8
Other possible failure mechanisms............................................................................................. 8 i.
Receiving member (bamboo beam or post) failure due to splitting. ..................................... 8
Foundations ............................................................................................................................ 9
iii. Tension failure of bamboo brace .............................................................................................. 9 7.
Knowledge dissemination ............................................................................................................... 9
Literature cited................................................................................................................................ 9
Appendix A (As-built Survey) ............................................................................................................... 10 Appendix B (Test Data) ......................................................................................................................... 12
1. Introduction SAFE (NGO) works in improvement low-cost housing in Bangladesh. Working primarily in Bamboo, SAFE strives to build stronger and longer lasting houses for low-income families. High-winds are one of the biggest hazards for housing in Bangladesh. SAFE has been providing bamboo cross-bracing to its bamboo framed houses to provide lateral stability. Testing of these bamboo bracing connections was undertaken, along with Structural Engineering Design Calculations, to provide an Engineering basis for future design and implementation.
2. Materials and methods Bracing bays are provided (as shown in figure 1) to every external wall, no more than 12' (3660mm) apart. Two sets of bracing are used (on either side of the posts) if the wall is shared between two houses or rooms.
Figure 1 Typical Bracing Bay
Half bamboo members are used to provide tension-only cross bracing. These half bamboo crossbraces are fixed to vertical bamboo posts or beams using M10 bolts and 32mm circular washers to construct bracing bays. By inspection, it was hypothesized that the weakest part of the bracing system would be this bolted connection between the cross brace and the post or beam (figure 2). The bamboo used in testing was of the same species, from the same cultivation area and had undergone the same treatment process as the bamboo used in SAFE construction.
Figure 2 in-situ bracing connection
Figure 3 test specimen
It was expected that the connection would fail in a 'pull out' mode, which is to say that Bolt A would pull out the end of the bamboo cross-brace. This hypothesis was reached because of; â€˘ the small edge distance between the bolt and the end of the cross brace in the direction of loading. â€˘ the high strength of the bolt compared to the bamboo. â€˘ the much larger size of the full-bamboo post/beam when compared to the half-bamboo cross brace. From conventional timber Engineering knowledge (which, as another naturally occurring, cellular material can be considered a reasonable comparison) it was assumed that the wall thickness of the test specimen would have a greater effect on its resistance to bolt pull out (and therefore strength) than the outer diameter of the test specimen. To best test this connection, it was devised to suspend an idealised connection or test specimen (figure 3) from a frame (figure 4) with a known weight attached. Weight and therefore force on the test connection would then be gradually increased until the connection failed.
Figure 4 testing rig
Picture 1 testing rig in use
3. As-built cross-bracing survey A survey was undertaken of completed SAFE demonstration houses to ascertain the section properties of as-built cross-bracing. Summary of findings all values in mm min end distance brace diameter brace wall thickness
max 30 57 9
average 150 73.8 75 63.8 18 13.5
The results of the survey show large variations in the size and wall thickness of cross-bracing members as well as end distance. 27% of braces were found to not terminate at a node. Full survey results can be found in Appendix B.
4. Results Due to time constraints and the limitations of working in rural Bangladesh, the testing was beset by problems with the testing equipment. In all, 13 tests were undertaken though only three can be said to have been completed successfully. Succesful tests Wall (mm) Ult. Load (kN) Reason for invalidation Test B3 10 8.13 Test C 11 6.48 Test E 14 8.17 Invalid Tests Test Ai Test Bi Test Ci Test A Test A2 Test A3 Test B1 Test B2 Test D Test F
15 9 13 15 15 15 10 10 11 11
0.9 2.09 3.52 1.04 2.82 7.62 4.72 3.95 4.98 7.22
craddle reached ground additional weight required loading hook failed loading hook failed ropes slipped beam failed bolt rotation in beam beam rotation loading bolt b pullout beam failure
The sample size is too small to give a scientific indication of joint performance but further testing is not possible at this time.
failure load (kN)
Bolted Bamboo Connection Testing Results 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00
test specimen wall thickness (mm)
Picture 2 test B3 under load
Picture 3 test B3 after failure
Picture 2 above shows a typical test specimen under load. Picture 3 shows the same specimen after it has failed due to Bolt A 'pulling out' through the end of the half bamboo test specimen. Nodes are visible at both ends of the test specimen. Full testing results can be found in Appendix B.
5. Findings a. Initial Initial testing was fraught with equipment failure though some early assumptions were quickly confirmed. Namely; I.
End distance (the spacing between the bolt and the end of the bamboo cross-brace in the direction of the load) has a significant impact on its load carrying capacity. From initial testing, it was decided that a 2" (51mm) minimum end distance would give significant additional capacity whilst still being reasonable to construct (greater end distances are sometimes not feasible due to conflict with door openings and other framing members).
Nodes. Bamboo has naturally occurring thickenings along its length from which shoots and leaves grow, known as nodes. These nodes are substantially thicker than the rest of the bamboo and also have a disrupted grain pattern. These physical characteristics provide an increased strength and resistance to bolt pull-out at the end of the bracing members. Therefore, all bracing members will be terminated at a node.
b. Load Capacity Using the limited test data available, a bolted connection strength has been reached by the following rationale; â€˘ The lower-bound of successful tests was 6.48kN â€˘ A connection safety factor (âˆ…) of 0.60 is deemed appropriate due to the uncontrolled nature of Bangladeshi construction, variability of materials and uncertainty due to the small testing sample size. = , Ă— âˆ… = 6.48 Ă— 0.60
= &. '()
6. Discussion a. Suitability of Load Capacity From 5. b. (above), a load capacity of 3.9kN has been ascertained for a single connection (including a 0.60 safety factor for connections). From structural analysis, it has been calculated that the likely (un-factored) force on this connection during wind loading is 2.32kN. 3.9 = 1.68 â‰Ľ 1.50 01234 5674 879:6;< âˆ´ ok 2.32
8 The value of 2.3kN has been determined from a design wind speed of 139km/h (35.5m/s). This design wind speed is based on the following conditions of IS 875:198722; 47m/s Basic Wind Speed 25 year design life terrain category three flat topography
b. Guidelines for construction From testing results and consideration of construction realities, the following parameters will be set for the construction of bamboo cross bracing; • All cross-bracing members must terminate in a node. • The end distance between the bolt and the end of the cross-bracing member must not be less than 2" (51mm) • The minimum wall thickness of bamboo to be used as a cross-bracing member is to be 3/4" (19mm) • The minimum outer diameter of bamboo to be used as a cross-bracing member is to be 2.5" (63mm) The minimum wall thickness prescribed above is significantly thicker than any used in testing. From experience, the use of thicker walled bracing will be achievable in practice and this will allow for some additional load capacity above that stated in this report.
c. Other possible failure mechanisms i. Receiving member (bamboo beam or post) failure due to splitting. During testing, failures were observed where Test Bolt A would rotate within the test beam resulting in the beam cracking longitudinally (picture 2). The testing involved the beam being loaded perpendicular to the grain (the weakest direction). In practice, the cross-brace will be placed at a 45⁰ angle and, therefore, the beam/post will be loaded at 45⁰ to the grain (as opposed to 90⁰ during the test). Studies have shown that bamboo's compressive strength is in the order of 4 times stronger in the direction of the grain (0⁰) than perpendicular to it (90⁰)1. Therefore, it follows that an increased strength magnitude of 2 could be reasonably assumed for loading at 45⁰ and applied to the testing results. From the two tests that failed due to bolt rotation and beam splitting (Test B1 and B2) the Picture 4 bolt rotation and cracking of test beam lowest strength ascertained was 3.95kN. However, this was using the same beam that had already split in test B1 where it achieved a load of 4.72kN and this would be a more accurate representation of the beams resistance to splitting. If a factor of 2 is applied to 4.72kN, a probable resistance of 9.44kN is found which is significantly higher than the lower-bound of 6.48kN used in the load capacity calculations pertaining to pull-out failure. Therefore this failure mechanism is assumed not to govern.
9 ii. Foundations After considering results of the bolted connection testing, it is now probable that the foundations (pre-cast concrete piles known as kaatlas) will govern the bracing design. However, design and testing of these kaatlas is outside the scope of this report.
iii. Tension failure of bamboo brace Tension failure of the half bamboo cross-brace itself is not expected to govern as this would have become apparent during tests. A short section of bamboo connected test bolt A from loading bolt B and would have served to test the bamboo tensile strength at the same time as testing bolt A.
7. Knowledge dissemination Findings from this testing will/have be actioned in three areas; • Structural drawings have been produced showing minimum dimensions and construction details of bracing for use in future SAFE projects. • This report will be made publicly available on the SAFE website. • A leaflet (in Bangla) has been produced and distributed to slum residents outlining construction requirements for cross-bracing. Refer to Figure 3 below for segment pertaining to dimensions of cross-bracing. The complete leaflet as well as an English draft can be found on the SAFE website (http://safebangladesh.wordpress.com)
Figure 3 section of Bangla cross-bracing leaflet
8. Literature cited 1. Mechanical and Physico-Chemical Properties of Bamboos carried out by Aerospace Engineering Department, Indian Institute of Technology – Bombay with Prof. NK Naik as Principal Investigator. Retrieved 16th June 2012 from http://www.bambootech.org/files/mechanicaltesting%20report.pdf 2. IS 875:19872. Indian Standard Code of practice for design loads (other than earthquake) For buildings and structures. Part 3 Wind Loads (Second Revision)
Appendix A (As-built Survey)
Appendix B (Test Data)
Appendix E Simple guidelines for cross-bracing - leaflet
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SAFE Bangladesh guidelines for better-building with Bamboo! Easy steps to help your house resist wind, earthquake, rain, last longer and save you Taka!
CROSS-BRACING By adding half pieces of bamboo cross bracing to your walls as outlined below, youâ€™re house will be stronger and resist high winds, storms and earthquakes.
! a p pŃ?
Where should I place cross-bracing? Cross-bracing should be added to EVERY external wall of your house. These walls should be no more than 12â€? apart. If they are, a middle wall will need to be braced TWICE. If house is two-stories, top story bracing should be placed directly above the bracing below.
How do I connect the bracing? A drill and M16 bolt with washer is required to connect each end of the cross bracing. You must be careful to have a node at the end of each cross brace and also have a minimum of 2” (50mm) from the bolt to the end of the cross brace. Connections are THE most important part of cross bracing What Bamboo should I use? Thicker bamboo is best but size should be at least 2.5” diameter and 3/4” wall thickness as shown on below; 2” (5
3/ (1 4” 9m m
0m m )
Roof Bracing Roof bracing is another easy way to strengthen your house. Add diagonal bamboo members to the corners at the top of your walls and fix with bamboo nails.
HANDY TIPS • Use bamboo treated against insect attack for longer lasting house (contact SAFE for more information) • Protect cross-bracing and all bamboo from rain and wind using CI sheet and careful planning. • Use concrete Katla foundation pads to prevent bamboo posts from rotting in the earth. • Mixing 5% cement with mud plaster will make walls and floor last MUCH longer. (more tips in Bangla RE: Maintenance) MORE INFORMATION SAFE Bangladesh promotes improved building techniques for low-cost housing in Bangladesh. By doing this, we help Bangladeshi’s build better and longer lasting houses, with their own hands! SAFE demonstration houses can be viewed in Jorgen Babur Mart, Dinajpur where you can see all of these techniques in action. If you have any questions, contact; Azit Roy xxxxxxxxxxxxxxxx Pulin Roy xxxxxxxxxxxxxxxx Masud xxxxxxxxxxxxxxxx
Appendix F Solar light bulb installation report
S. G. Stephens BE (Hons) June 2012
MEMORANDUM ON INITIAL TRIAL OF SOLAR BOTTLE BULB IN JORGEN BABUR MART SLUM, DINAJPUR, BANGLADESH Prepared by S. G. Stephens 7th June 2012 for SAFE Bangladesh (NGO) Pictures and video by Marianne Keating
INTRODUCTION SAFE Bangladesh is a small NGO working primarily in the low-cost housing sector in North West Bangladesh. As part of their work improving quality of life through improved building techniques, SAFE has started to experiment with using water-filled plastic bottles to provide low-heat and electricity-free lighting.
OVERVIEW OF INTIAL TRIAL Intial trial bulb was installed 6th June 2012, at the house of local slum builder Delowar. As this was an initial trial, bulb was placed near wall where it would be less-effective but where it could be placed through a small section of rather tired corrugated iron (CI) sheet that could be easily replaced. A 2L coke bottle was filled with a mix of boiled water and approximately 250ml of Clorox liquid bleach purchased in Dhaka. Bangladeshi bleach seems to be far weaker than the equivalent in the UK. The bottle of Clorox states an active ingredient (Sodium Hypochlorite) concentration of >5,25%. Taking the label at its word, the bottle bulb should contain approximately 6.5ml of Sodium Hypochlorite per liter. The bulb was initially placed and sealed into a small 500x500 section (or 'patch') of CI sheet using McCoy General Purpose Acetoxy Silione Sealent purchased from a glaziers in Dinajpur. After curing, a hole was cut in the roofing CI sheet and the bottle and 'patch' sealed on top.
Bottle and CI sheet 'patch' before sealing
Cutting hole in roofing sheet
S. G. Stephens BE (Hons) June 2012
Sealing between patch and roof sheeting
INTIAL COST ESTIMATE
Intial Cost Estimate of Solar Bottle Bulb In Dinajpur, Bangladesh (June 2012) Item Silicone applicator gun Tin Shears
Cost BDT 400 BDT 100
2nd hand plastic bottle Silicone 280ml tube Bleach (1L 5.25% NaOCl) CI sheet 'patch'
BDT 10 BDT 250 BDT 210 BDT 500
No. Bulbs Cost/Item ignored ignored 1 2 4 10
BDT 10 BDT 125 BDT 53 BDT 50 BDT 238
238BDT/bulb is possibly too expensive for the Solar Bottle Bulb to be widely adopted in JBM slum. The following areas could produce savings in the cost of each bulb; 1. Finding a cheaper silicone or sealant, possibly in bulk with a brush application. Important qualities for the sealent are; elastic, bonds to steel and plastic and resistant to water, sun and elevated temperatures. 2. Finding a cheaper and locally sourced bleach. 'Bleaching powder' was found in Dinajpur though this powder had only very week concentrations of Chlorine and was cut with an insoluble powder that would make the bulb ineffective. Bleach needs to be found with as little colouring as possible, the Clorox used in the test has a slight yellow tinge which coloured the bulb. 3. Using second hand CI sheet to form the patches. This was done for the initial test bulb though it is hard to discern a cost for such a second hand item and new CI sheet prices are used in the calculation above.
S. G. Stephens BE (Hons) June 2012
RESULTS Once placed, the bulb was very bright and provided a large amount of light into the previously very dark room. Please refer to http://youtu.be/rlS17jVZ6s0 for a visual demonstration of effectiveness. The installation will be monitored over the upcoming Bangladesh rainy-season to evaluate effectiveness and durability of sealing system used.
Room interior with Solar Bottle Bulb covered
Room interior with Solar Bottle Bulb un-covered
S. G. Stephens BE (Hons) June 2012
COMPARISSON TO OTHER LIGHTING ALTERNATIVES CLEAR PLASTIC CI SHEET One strip or even a short section of clear plastic corrugated sheet provides large amounts of light into a room. A 7' sheet costs 700BDT which is approximately 1.5times the cost of the thick CI it replaces. So, this is not inordinately expensive yet there is not one house in the slum where this has been used. Possible reasons for the clear plastic sheet not being adopted are; â€˘ Heat. A small, 1'x2' section of the plastic sheet was installed in a SAFE demonstration house and provided a lot of light though the owner complained about the heat. â€˘ Frailty and durability. The plastic sheeting is seen to be weaker than the CI sheet it replaces and is likely to get dirty. Comparing cost; A 2'4" x 2'6" clear plastic corrugated sheet suitable to make a skylight costs about 233BDT which is comparable with the 238BDT it cost for the initial trial solar bottle bulb. It is hoped that the cost of the bottle bulb can be significantly reduced and that it performs better that the plastic corrugated sheeting in terms of heat and durability therefore making the solar bottle bulb a viable alternative.
ELECTRIC BULB Almost all the houses in the slum use at least one electric bulb, sometimes through an illicit connection. The electric bulb works at night while the solar bulb obviously won't. This disadvantage is somewhat mitigated by the fact that the electricity supply is very intermittent. During peak irrigation season, rural areas of Dinajpur can receive as little as a few hours of electricity each day while the sun shines almost perpetually. Comparing cost; From a recent electricity bill, the current price of electricity in Dinajpur appears to be 4.2BDT/kWh (1/6th of the price in the UK). Assuming a 50watt bulb is used for 6 hours each day;
0.060 Ă— 6â„Ž Ă— 4.2 = 1.512 â„Ž At the initial solar bottle bulb cost of 238BDT, the payback period is about 5Â˝months. It is hoped that, by reducing the cost of the solar bottle bulb, the pay-back period can be reduced and the financial advantage increased. The cost of a traditional tungsten filament bulb is only 22BDT. If we consider a 5watt energysaver bulb, the pay-back period jumps to over 5years. However, the initial cost of an energy saver bulb is approximately 250BDT and therefore more expensive than the solar bottle bulb. An energy-saver bulb will also be susceptible to the sporadic electricity supply.
S. G. Stephens BE (Hons) June 2012
LESSONS LEARNED AND KNOWLEDGE GAINED 1. Bulb is effective yet expensive (â‰ˆ240BDT). Steps described earlier in 'Initial Cost Estimate' could significantly decrease cost and improve likelihood of technique being adopted. 2. A cheaper and possibly simpler form of sealant needs to be found locally. 3. A cheaper and possibly 'clearer' bleach or disinfectant needs to be found locally. 4. Monitoring and experimentation is required to see which concentrations of which bleaches/disinfectants are most effective and affordable. 5. It is important to use good quality CI sheet for the patch as well as select a good piece of receiving CI sheet on the roof. This is because worn CI sheet can have a less-pronounced or deformed corrugation profile and therefore be difficult to seal. 6. It is important to center both the hole in the patch and the hole in the receiving sheet to the same orientation of the corrugations. i.e. a corrugation ridge should correspond to the centerline of both the hole in the patch and the receiving sheet. 7. Financial and other advantages of these bulbs are currently not very convincing to slum residents. Further study is required to produce a stronger case to submit as to "why?" they should install a solar bottle bulb.
LONG-TERM VISION It is hoped that one or more of the local Jorgen Babur Mart slum builders (Delowar, Masud or Baush) can be trained how to install solar light bottles and do so for a reasonable price while earning some money for themselves. In short, to create a small entrepreneurial business to provide improved lighting throughout the slum.
Appendix G Location key plan of households & interview of household
Shujon Chandra Dash
Shujon going to work
wife growing vegetable
Shujon Chandra Dash: Shujon is the youngest son of Durgoty Das and Zudhishti Chandra Dash. He has 2 sisters and 2 brothers. All his siblings have now moved away and Shujon lives here with his wife, 2 young children and his mum and dad. Shujon works as a day labourer for pond owners outside Dinajpur who farm fish. His work involves catching the fish, maintaining the nets (often involves diving 20-25 ft to the bottom) and cleaning the water. In off season he repairs hemp sacks (bosti). The daily wage he gets from the fish farm varies from 40 taka ($0.5) to 300 taka ($3.5) but on average he will earn $ 35-40 per month. From this, and the income that his wife earns from rolling poppodoms, they support their family and also his aged parents. His dad is partially sighted and though he does look old he does not look the 101 years that Shujon claims! In January 2012, his father suddenly went missing. The whole family searched all over – the neighbourhood first, then the whole town. Exasperated, they went to seek the advice of fortune tellers. The first advised that he might have gone to Dhaka and so Shujon made the journey and visited friends in the capital but his dad was not to be found. The second
fortune teller advised him that his dad was " in a place from where if was difficult to come back to Bangladesh". On month later, news reached Shujon that his father had been found at his sister’s house in India. Without telling anyone, and without any papers or money, he had managed to cross the border in India, was arrested by the border police and kept in jail for 12 days. Finally the police took pity on his and let him go – one even gave him 150 taka. And so he managed to make his way to his sisters house.
Giribala: Giribala has one son and one daughter and is in her late 50s. Her son stays in Dhaka where he earns money as a rickshaw puller – he can earn much better money there. Giribala works as maid in two houses. Each day she will spend two-hour morning shift for washing clothes, cleaning the floor in a 4room house. She cuts the vegetables and does all the food preparation before the cooking begins. As a monthly wage, she get 350 taka ($5) from each of the houses, including a daily allowance in the form of breakfast and lunch. In the one-hour evening shift, she does almost the same amount of work, but does not get any allowance in the form of food. She is living with her daughter, who is about to get married. The new house will increase social value for her daughter's marriage.
After the 1971 Liberation War, Surujban came to stay in Jorgen Babu Marth, from Gaibandha district and started staying rental houses surrounding the field. Her main livelihood is making poppodoms. In the first step, the vendors give the balls of raw dough and she rolls them and lets them dry under the sun. In the second step, she has to repeat the whole process again to make the poppodom thinner and wider. In the dry season, she makes 500 poppodom for 50 taka ($0.60) per day. Her son and daughter-in-law earns 200 to 300 taka in off-season (rainy season) and approx 500 taka per day as brick layers during the construction season. They rent out their three-wheeler rickshaw â€˜vanâ€™. Surujban has the intention of saving so with the money she saved from her per diem from the SAFE Workshop, she brought a goat. The goat is now pregnant and she hopes to get two to three baby goats a year which she can sell.
Saidul Rahman, an Ice-cream vendor in his early 50s has got two daughter and a son. In the winter season, he collects recycling material from door to door in the exchange of his peanuts & pickle. He also sells ice cream around the local area. He works weekly four-to five days a week and earns around 250 taka ($3.00) per day. His eldest daughter got married at the age of 12. He says that if his daughter remained single beyond this age then there might be problems â€“ like she may have an affair. His other daughter, Shathi, is of sixteen years old and is disabled. Shathi was a normal child at birth with only a little working disability with her left hand, but at the age of nine month, was attacked by severe fever which made her lose her vision and left difficulty in her hearing. Over the years, she did regain her vision, but she never learnt to talk. She could still walk holding walls, doors and other kinds of vertical supports, but three years ago she had a severe road accident which took her ability to walk even. All of her family members including her younger brother have to feed her meals three times a day. Sometimes when all the family members are out to work, they tie her leg to the bed stands with rope, so that she does not go crawling around, getting herself hurt. A local NGO has given Shathi a wheelchair to help her become more mobile.
\ Rubi Begum came to Dinajpur after the Liberation War of 1971. She is Muslim. She got married at the age of 13 and had a 9‐years of married life before she became widow with a 2 1/2 year old son and was pregnant with her daughter. Soon enormous pressure was exerted on her to get married again and so she ran away from her home in Gaibanda leaving her son to be looked after by her mother. She worked as a maid for the first year, and then started to work as a day‐labourer, doing jobs in construction work, earth excavation, and at the rice mill factory. As she was young, it became really hard for her to work due to indecent verbal abuse from her male co‐ workers. She left these jobs and started selling door‐to door glass‐bangles, laces and necklaces. (Her Hindu neighbour sold bangles previously and taught her) Still is still doing this vendor work. She never gave up the fight and says her children were her inspiration to keep‐going in her life. Her daughter and son‐in‐law stay with her, and two grandchildren. In this new two‐storey house, she has now some space of her own to pray, do her vegetable gardening, as well as dry to poppodom in a hygienic way (i.e not in the street) on the verandah.
Dhirinchondro Ray was the actual owner of this land and house for the last ten years. Shabitribala was his wife's younger sister who has been living with them ever since she became a widow. Shabitribala has a one son and one daughter. Before the construction of this new demonstration house started Dhirinchondro Roy’s wife, Rongobala died suddenly. Couple of months later, after the new house was about to be finished, Dhirinchondro ran away to Dhaka to re‐ marry another elderly lady from Dinajpur. He left this house to Shabitribala and her children.
Shabitribala walks with difficulty following and earlier accident but she still works as maid. Shujon, son of Shabitribala, got married recently with a handsome dowry and is happy that he can use some of this money so that he may be able to help his sister into a good marriage. During the off‐season (rainy season), he repair's hessian sacks used for rice and other agricultural produce. During the dry season, he does fishing for the local pond owners earning 3000 to 4000 ($35‐$40)taka per month. This new house has allowed enough space for all kinds of functions including a room for Shabitribala, one for Shujon and his wife, a prayer space and vegetable gardening.
Beauty got married in her early teens and she moved with him to Dhaka. She says that a month after arriving in Dhaka she realized that her husband was trying to sell her off to sleep with other men. With the help of her cousin, she escaped from Dhaka and came back to mother's home in Dinajpur. Her parents didn't believe her. When husband came back, he convinced her family that everything was fine and stayed with them for two to three months, after which she fell pregnant with their first child. He then fled for 4 years without any trace. When he came back again, he told that he has been in prison all these years but was now a changed man, and Beauty again took him in. Unfortunately after 2.5 years he left again, this time for good and without a trace, leaving her pregnant with her second son, Akash (sky). During this period she earned her living from a variety of jobs including breaking bricks on construction sites and cleaning govt. drains. Due to social pressure, she had to remarry again and had a third son, Prem. This man was also unfaithful to her and when his activities got exposed he also left Beauty for good. Beauty with her two elder sons together earns about $5.00 per day. The two eldest sons stopped school so they could work to earn money for their mum. They work repairing jute sacks while Beauty now earns her living by selling deep fried snacks around the neighborhoods.
Nurjahan: Nurjahan got married when she was very young. She had two daughters and then her husband fell very ill. After suffering severely for couple of years, the illness at last took its toll and he passed away. Money was short and she didn’t even have enough money to pay for the funeral. As a widow she has found it difficult to earn money and she moved back to her father's house with her daughters. Within a few years her father also died and it was not possible for her to stay with her step‐mothers family. At certain time, Nurjahan started to beg around Dinajpur town. Later on, she became a day labor for quite a long time. Now she works as maid at some households and earns 600 taka ( $7) per month as well as some food from the houses.
Bhogoboty got married around 30 years back witt Atul Proshad Roy when she was 23. After 10 years of her mariage her Atul got married with Bhogobotie's younder sister and all stayed together in the same family for 12 years. Even though B didnâ€™t like Bhogoboty has got one son and three daughters and her sister has got one son and a daughter. Bhogoboty stays with her son now as and her hunsband comes to visit some times as he went to another house eight years back to stay with his younger wife. Bhogoboti cannot stop comming of her husband as their son requested that how can they deny the person who has given birth of them. She was involved in workshops of diffent ngos. She takes small loans from the N.G.O.s and buys clothes like saree and lungi from the retail market and sells to door to door as her profession. A monthly 2500 taka ($30) is her average income from this. She feels like at least she is not totally dependend on someone. Her son giot married at the age of 16. He stays at the same house with his wife. He works as sales man in a auto flower mill earning 3500 taka ($ 42) per month. Bhogoboty loves groing vegetables and plants. Wherever she could, she grew lots of vegeables. She also does three times prayer everyday in her praying space with hidu daities and their pictures.
Appendix H 3-day design workshop programme
11.05.11/JA Simple Action For the Environment (SAFE) Design Workshop – Jorgen Babur Mart community, Dinajpur, 15-17th May 2010 3 day design workshop with 10 members of the community of Jorgen Babur Mart, architects, engineers, carpenters and builders. Objectives: to build trust between partners; learn about building-for-safety techniques appropriate to the context of Jargon Babur Mart, develop designs for our proposed houses within a specific budget; produce an outline plan for construction. 15.05.11 Day 1 –Existing good practice 10:00 – 10:30
Introduction – getting to know each other. Objectives (see above) Activity – each household draws their house on the map. SAFE – about us
10:30 – 13:30
What is a hazard? What is a disaster? Activities – brainstorm different hazards and then in groups think of ways to design your houses to overcome them. Followed by short presentation by groups on their findings.
13:30 – 14:30
Lunch Good practices of resilient low-cost housing in Bangladesh, relevant to Jorgen Babur Mart context. Including
Bamboo treatment Lighting and ventilation – windows; natural ventilation; improved cook stove Stronger frame – improved bamboo joints; cross-bracing; concrete foundation posts (kaatla) Walling materials and heat Cement stabilisation for earthen plinth Growing vegetables
16.05.11 Day 2 – Initial design 10:00 – 10:30
Welcome and review of good practices from yesterday afternoon. Objectives for today.
10:30 – 13:30
Design house for Jorgen Babu Mart (2 groups). Activities include:
Presentation by architect students to groups about initial designs. Model building Groups to focus on different sized houses
13:30 – 14:30
14.30 – 16:15
Continue to develop design, incl. cost analysis of each house option (2 groups)
16:15 – 17:00
Informal presentation from each group about each house option
17.05.11 Day 3 – Design review and implementation 10:00 – 10:30
Welcome, objectives for today.
10:30 – 12:30
Design development including revisions with respect to costs.
10:30 – 12:30
Singing with song team
12:30 – 13:30
Presentation about each house option including costs.
13:30 – 14:30
14.30 – 16:30
Implementation and management
16:30 – close
Certificate award ceremony
Published on Jul 20, 2013
(February 2013 / J. Arnold) A report on the design and construction of 10 demonstration, low-cost houses in a slum area of Dinajpur.